A Technical Guide for Forest C-l Nursery Management in the

ia. United States{@i&j pv;;;;;t of-\

Forest Service

A Technical Guide for Forest C-lNursery Management in the

Southern ForestExperiment Station

New Orleans,Louisiana

Ck&~~~l Technical ReportLeon H. Liegel and Charles R. Venator

An Institute of Tropical Forestry publication in cooperationwith the University of kJeti0 RiCO

1

ACKNOWLEDGMENTS

The authors deeply appreciate the cooperation and personal assistance of numerousForest Service colleagues who were involved in the development and completion of thisguide.

Also, special appreciation is extended to Dr. C. B. Davey, Forestry Department, NorthCarolina State University, and Mr. Donald Thompson, Senior Research Officer, UnitedKingdom Forestry Commission, for their efforts in reviewing the manuscript: and to Dr. M.Robbins Church, Environmental Protection Agency, Corvallis, OR, for making completionof the draft possible at that location.

Finally, the authors gratefully acknowledge the contributions of those administrative andtechnical personnel of the following organizations who shared their knowledge of variousnursery practices with the authors and allowed them to photograph ongoing nursery work:Compania National de Reforestation (CONARE), Estado Monagas, Chaguaramas,Venezuela-large-scale bare-root operations; Forest Industries Development Corporation(FIDCO), Kingston, Jamaica; and The Department of Forestry and Soil Conservation,Kingston, Jamaica-large-scale, labor-intensive container operations.

.

This manual is the product of 20 years of nursery, plant physiology,and plantation research programs at the Institute of Tropical Fores-try, Southern Forest Experiment Station, ,Rio Piedras, Puerto Rico.The research was conducted in cooperation with the University ofPuerto Rico.

October 1987

CONTENTS

CHAPTER 1

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.1 Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.2 Audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.3 Subject Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.4 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.5 Source Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.6 Physical Setting.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.7 Dedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C H A P T E R 2

2. REVIEW OF REGIONAL NURSERY PRACTICES . . . . . . . . . . . . . . . . . . . . . . . . . .2.1 PuertoRico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1.1 Traditional Ap roaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1.2 Nursery ConsoPidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1.3 Nursery Centralization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1.4 The CatalinaNursery.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.15 The Experimental Nursery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2 The Caribbean and Tropical Americas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2.1 Traditional Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2.2 Non-Traditional Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


C H A P T E R 3

3. NURSERY SITE SELECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.1 Climate and Environment3.2 Location and Essential Facikies * : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : :3.3 Soils and Topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3.1 Physical Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.2 Chemical Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

;$ Fi;terSupply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

316 Labd;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::3.7 Nursery Equipment and Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

LITERATURECITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C H A P T E R 4

4. DESIGN AND LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.1 Production Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.2 Administrative/Employee Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.3 Storage-Shipping-Receiving Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.4 Operational Areas.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.5 Herbicide and Insecticide Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.6 Laboratory Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.7 Utility Lines .... .._ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.8 Protection

4.8.1 Windbreaks’:::::::::::::::::::::::::::::::::~~:::::::::::::::::::::4.8.2 Shade and Nursery Bed Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


CHAPTER 5

5. PRODUCTIONSCHEDULING.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.1 General Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.2 Some Specific Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

i

CONTENTS (Cant)5.2.1 Overall Planning and Coordination5.2.2 Disease

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.2.3 Seedling Growth Rates22

. . . . . . . . . . . . . . . . . . . . . . . .5.3 ACaseExample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

CHAPTER 6

6. SEED PROCESSING AND STORAGE 246.1 FruitTypesandProcessingPractices’:::::::::::::::::::::::::::::::::::: 246.2 Cones and Dry Fruits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.2.1 InitialInspectionandHandling..6.2.2 Air-Drying

. . . . . . . . . . . . . . . . . . . . . ::::::::::::::: :t. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.2.3 Kiln-Drying62.4 Solar Dryers

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

6.3 FleshyFruits ... . . . . . . :::::::::::::::::::::::::::::::::::::::::::::::::6.4 Moisture Content Considerations

2

6.5 Cleaningandstorage...........::::::::::::::::::::::::::::::::::::::: : ;;


CHAPTER 7

7. SEED TESTING7.1 Sampling

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.2 Weight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.3 Purity Analysis

30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.4 Moisture Content30

7.5 GerrninationPotential’::::::::::::::::::::::::::::::::::::::::::::::::::7.5.1 Germination Test Procedures

ia

7.5.2 Seedling Evaluation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

. . . . . . . . . . . . . . . . . . . . . . . .7.6 OtherSpecialTests.. . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.6.1 SeedVigor:::::::::::::::::::::::: 33;

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.6.2 IndirectIndicesofSeedVigor.. . . . . . . . . . . . . . . . . . . . . . . . . . ::::::::::::: ;;

LITERATURECITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

CHAPTER 8

8. SEED PRESOWING TREATMENTS8.1 Breaking Seedcoat Dormancy

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

8.1.1 Acid Scarification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

8.1.2 Water Soaking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

8.2 MechanicalScarification’::::::::::::::::::::::::::::::::::::::::::::::::8.3 StratificationMethods

ii

8.3.1 Cold Stratification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

8.3.2 ChemicalAlternati;es’:::::::::::::::::::::::::::::::::::::::::::::: it


CHAPTER 9

9. TRADITIONAL SEEDBED PREPARATION AND SOWING9.1 Container Systems

. . . . . . . . . . . . . . . . . 37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.1 Selection Criteria37

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379.1.1.1 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379.1.1.2 Shape/Volume Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.2 Selecting and Preparing Pot Media38

9.1.3 Filling Pots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389.1.4 Direct-Seeding Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389.1.5 Transplant Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

9.1.5.1 Germination Media9.1.5.la Sand/Soil.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i:9.1.5.lb RiceHulls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

ii

CONTENTS (Cant)

9.1.5.lc Vermiculite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.1.5.ld Tissue Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.5.2 Sowing and Germinating9.2 Bare-Root Systems

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1 Selectioncriteria’::::::::::::::::::::::::::::::::::::::::::””””:9.2.1.1 Advantages and Disadvantages

9.2.2 Bed Orientation. . . . . . . . . . . . . . . . . . . . . . . . . : : : : : : : : .

9.2.3 Fallows. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.4 Cultivatibn’:::::::::::::::::::::::::::::::::::::::::::::::::::::::::9.2.5 Sowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.2.6 Mulching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


C H A P T E R 1 0

10. TRADITIONAL EARLY TENDING OF SEEDBEDS AND CONTAINERS10.1 Container Systems

..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10.1.1 Transplanting10.1.1.1 Timing..

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . :::. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..... . . .

.

10.1.1.2 Procedures.

10.1.2 Resowing10.1.3 Watering

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10.1.4 Shade. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10.15 Weeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10.2 Bare-Root Systems. . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10.2.1 Watering10.2.2 Shade

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10.2.3 Weeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ::i:::::::::::::


C H A P T E R 1 1

45

51

11. TRADITIONAL LATER TENDING OF SEEDBEDS AND CONTAINERS11.1 Container Systems

.... 52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11.1.1 Grouping, Sizing, andLining-Out.. . . . . . . . . . . . . . . . . . . . . .11.1.2 Inoculation With Mycorrhizal Fungi

:::::::::::: Ez

11.1.3 Watering11.1.4 Weeding

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11.1.5 ShootandRootGrowthControl.. . . . . . . . . . . . . . . . . . . .11.1.6 Lifting and Transporting

:::::::::::::::: ii

11.2 Bare-Root Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11.2.1 Inoculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ::::::::::: it

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.2.2 Watering11.2.3 Weeding

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11.2.4 Shoot and Root Growth Control . . . . . . . . . . . . . . .11.2.5 Lifting and Transporting

: : : : : : : : : : : : : : : : : : : : : : Ei

11.2.6 Stump Planting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.3 OtherLaterTendingConsiderations.. . . . . . . . . . . . . . . . . . . . . .

11.3.1 Shoot/Root Ratios::::::::::::: ::

11.3.2 Hardening-Off. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

. . . . . . . . . . . . . . . . . . . . . . . . . _.11.3.3 Culling J-Root Plants

. . . . . . . . . . . . . . . . . . . . . . . . . . 57. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58


C H A P T E R 1 2

12. PROTECTION AND PEST CONTROL12.1 Property and Seedling Security

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

12.2 Pests and Diseases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

12.2.1 Symptorns.....::::::::::::::::::::::::::::::::::::::::::::::::::: :12.2.2 Control

ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12.3 Common Chewing Pests60

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.3.1 PineSeedlingCutworm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ::::::::::::: s6:

..*111

CONTENTS (Cant)

12.3.2 Crickets and Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.3.3 LeafMiners

62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12.3.4 Shoot and Root Borers62

12.4 CommonSuckingPests. ..:::::::::::::::::::::::::::::::::::::::::::::12.4.1 Aphids..

:;. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12.4.2 Mealybugs62

12.4.3 Thrips. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.4.4 Scales and Mites

62

12.5 Larger Pests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.51 Spiders12.52 Birds

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . :ian8.~...ce.::::::::::::::::::::::::: :::::::::. . . . . . .12.5.3 Rats .::. . . . . . .

12.6 Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.6.1 Damping-Off

. . . . . . . . . . . . . . . . ..

.:

. . . . . . . . .z63

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.6.2 SeedlingNeedleBlight.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.6.3 Brown Needle Disease

:::::::::::::: :i

12.6.4 PurpleFoliage12.65 Root Rot

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64


C H A P T E R 1 3

13. NURSERYNUTRITION.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

13.1 Essential Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13.2 Nutrient Deficiency Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13.3 Foliage (Tissue) Sampling

: : : : : : : : : : : : ::

13.4 SoilTests... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13.5 Special Soil Problems: Acidity and Salts . . . . . . . . . . . . . . . . . .13.6 Fertilizers

.,I : : : : : : : : : : : : ::. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13.6.1 Mixing Fertilizers With Growing Medium . . . . . . . . . . . . . . .13.6.2 Using Soluble Fertilizer Mixes

: : : : : : : : : : : : ;:

13.6.3 Formulating Nutrient Solutions on Site’ : : : : : : : : : : : : : : : : : : : : : : : : : : : : : zi


C H A P T E R 1 4

14. NURSERY EXPERIMENTATION . . . . . . . . . . . . . . . . . . . . . .14.1 PlanningtheExperiment . . . . . . . . . . . . . . . . . . . . . . . . . . .

14.1.1 Traits Assessed..::::::::::::::::::: ;z

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14.1.2 Sources of Variation

76

14.1.3 ExperimentalProcedures’:::::::::::::::::::::::::::::::::::::::::::14.1.3.1 Restricting Experiment Objectives

;:. . . . . . . . . . . . . . . . . . . . . . . . . . . .

14.1.3.2 Replicating the Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : :14.1.3.3 Randomly Assigning Treatments

;;

14.2 Experimental Design Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

14.2.1 PlotShape14.2.2 Plot Size

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ;:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14.2.3 Border, Surround, or Edge Rows78

14.2.4 Number of Replications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14.2.5 Experimental Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : : : : : : : : : :

14.2.5.1 Completely RandomEi

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14.2.5.2 Randomized Complete Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : :14.2.5.3 Latin Square

;s

14.2.5.4 Split Plot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14.3 Data Recording and Record Keeping

80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14.3.1 Data Recording Do’s and Don’ts81

14.3.2 Basic Statistics and Data Summarization : : : : : : : : : : : : : : : : : : : : : : : : : : : : ii


iv

CONTENTS (Cant)

C H A P T E R 1 5

1JTERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . .

CI IAPTER 16

15. MECHANIZED CONTAINER PRODUCTION15.1 CriteriaforSelectingContainers

151.1 Length. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15.1.2 Shape.......................................::::::::~~~~~~~~~~ ....15.1.3 Volume/Design Influences on Roots . . . . . . . . . . . . . . .I I I I 1: : : : 1: : : : : : : :_-.- -.-

15.1.3.1 Ribs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15.1.3.2 Holding Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15.1.3.3 Drainage/Root Egress Openings . . . . . . . . . . . . . . . . .

15.1.4 Container Construction Materials . . . . . . . . . . . . . . . . . . . : : : : : : : : : : : : : : : :15.1.5 Container Systems: Some Historical Perspectives15.1.6 Maior Container Svstems of the 197fYs rind 1

_ _ . _ I . . . . . . . . . . . . . . . . . . . .

15.2 Selecting Growing Me&&~-- - - - - - - - - . - I - - - - - 980’s . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .

15.2.1 IdealMediumProperties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ::: . . . . . .15.2.1.115.2.1.215.2.1.315.2.1.415.2.1.5_--. -

PeatVermicuiite ’ 1: 1:Perlite . . . . . . . . .Sugarcane WasteRice Hulls . . . . . .-

...............................................

...................... . . . . . . . . . . . . . . . . . . . . . . . . .

.............................................................................................

...............................................15.X1.6 Compost . . . . . . . . . . . . . . . . . . . . . . . . . . .15.2.1.7 Wood Products . . . . . . . . . . . . . . . . . . . . .

15.2.2 Optimum Growth Medium15.2.2.1 Porosity and Aeration Cbnside&dns15.2.2.2 Examples of Mix Proportions . . . . ,15.2.2.3 Synthetic Mixes . . . . . . . . . . . . . . . .

........ . . . . . . . . . . . . . . . . . . . .

............................

........................ . . . ........

__.............................

15.3 BasicEquipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...““’15.3.1 Compost Shredders . . . . . . . . . . . . . . . . . . .15.3.2 Soil and Compost Sievers . . . . . . . . . . . . .15.3.3 Medium Mixer15.3.4 Potting Machine’ : : : : : : : : : : : : : : : : : : : : : :15.3.5 Semi-Automatic Seeder15.3.6 FinalFiller . . . . . . . . . . . :::::::::::::::15.3.7 Forklift and Wagon . . . . . . . . . . . . . . . . . . .

15.4 Other Operational Techniques15.4.1 Medium and Facility Sterilization * : : : : :15.4.2 Filling Container Cavities . . . . . . . . . . . . .15.4.3 Sowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15.4.4 Lining-Out and Germinating

15.4.4.1 Stacked Method . . . . . . . . . : : : : : : : : : :15.4.4.2 Lined-Out Method

15.4.5 Thinning, Transplanting] and Grading’ :15.4.6 Later Tending Care . . . . . . . . . . . . . . . . . . .

15.4.6.1 Moisture and Fertilizers15.4.6.2 Protection and Pest Cont&i : : : : : : : :15.4.6.3 Inoculation With Mycorrhizal Fungi15.4.6.4 Root/Shoot Growth Control

15.4.7 Lifting, Packing, and Transporting ’ : : : :

......................... ., . . ................

......... ....................

......... ....................

.............................

.............................

.............................

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.............................

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.............................

.............................

..........................

.................... .

....... . . . . . . . . . . . . . . . . . . . . . . . . .

.............................

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

16. MECHANIZED BARE-ROOT PRODUCTION16.1 Bed Preparation . . . . . . . . . . . . . . . . . . . . . . . . .

16.1.1 Plowing and Disking . . . . . . . . . . . . . . . . .16.1.1.1 Soil Compaction . . . . . . . . . . . . . . . . .16.1.1.2 Deep Plowing and Ripping . . . . . . . .

16.1.2 Fallows and Cover Crops . . . . . . . . . . . . .16.1.3 Mounding . . . . . . . . . . . . . . . . . . . . . . . . . . .

16.2 Fumigating . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16.2.1 Methyl Bromide Procedures . . . . . . . . . .16.2.2 Other Considerations . . . . . . . . . . . . . . . .

16.3 Seed Sowing . . . . . . . . . . . . . . . . . . . . . . . . . . . .16.3.1 Sowing Procedures . . . . . . . . . . . . . . . . . . .

..............................

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9”::z9”;1;:100100101101

CONTENTS (Cont)

16.3.2 Planting Densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10116.3.3 Mulching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

16.4 Tending Seedlings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10116.4.1 Herbicides 10116.4.2 MoistureCo;;S’id;?ratidnE!‘::::::::::::::::::::::::::::::::::::::::::: 102

16.4.2.1 Watering Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10216.4.2.2 Irrigation Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

16.4.3 Repellents and Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10516.4.3.1 Seedcoat Repellents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10516.4.3.2 General Pesticide Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

16.4.4 Fertilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10516.4.5 Inoculation with Mycorrhizal Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10516.4.6 Root Growth Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

16.4.6.1 Wrenching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10516.4.6.2 Lateral Root Pruning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10616.4.6.3 Undercutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

16.4.7 Shoot Growth Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10716.4.7.1 Top Pruning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10716.4.7.2 Hardening-Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

16.5 Lifting and Transporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10716.5.1 Historical Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10716.5.2 Lifting.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10816.5.3 Grading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10816.5.4 Packaging and Delivering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

LITERATURECITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

APPENDICES-The Why and How-To-Do-It Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Appendices are not ordered consecutively but refer to actual chapters where a major topicis discussed. For example, the first is Appendix 4 because shading and nursery bed orienta-tion are discussed in Chapter 4.

4. Shading Procedures for Small, Covered Nursery Beds in Tropical Areas . . . . . . 1135. Flow Chart for Scheduling Mechanized Production of Container

Nursery Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1156. Non-Oven Procedures for Drying Pine Cones, Mahogany Pods, or Similar Seed-

Bearing Fruits at Traditional Nurseries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1178. Summary of Seed and Nursery Characteristics for Forest Tree Species Commonly

Growing or Planted in Tropical and Subtropical Regions . . . . . . . . . . . . . . . . . . . . . 1199. Practical Guides for Fumigating, Sowing, and Transplanting . . . . . . . . . . . . . . . . 125

I. Recommended Procedures for Use and Storage of Soil Fumigants .... 126II. Calculation of Materials Required for Producing 1 Million Bagged

Pine Seedlings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129III. Sowing and Transplanting Procedures for Important Species of

TropicalTrees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130IV. Publications on Particular Tree Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

12. Practical Guides for Using Herbicides and Pesticides . . . . . . . . . . . . . . . . . . . . . . . . 133I. Herbicide Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

II. Pesticide Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137III. Procedures for Calculating Solution Concentrations . . . . . . . . . . . . . . . . . 138

13. Guides for Applying Fertilizers and Preparing Compost . . . . . . . . . . . . . . . . . . . . . 139I. Important Fertilizer Facts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

II. Procedures for Building a Compost Pile . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

vi

CONTENTS (Cant)

15. Specialized Facts for Container Stock Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145I. List of Container Manufacturers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

II. Five Types of Containers that are Useful in Tropical Countries . . . . . . 148III. Suppliers of Commercial Potting Mixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150IV. Split-Level Nursery Operations for Producing Container Stock . . . . . . . 151

16. Practical Guides on Watering and Soluble-Fertilizer Application . . . . . . . . . . . . . 153I. Water System Alternatives for Forest Nurseries . . . . . . . . . . . . . . . . . . . . 154

II. General Management Scheme for Watering Nursery Seedlings . . . . . . . 155III. Injector Alternatives for Soluble-Nutrient Watering Systems . . . . . . . . 156

vii

A Technical Guide for Forest Nursery Management in theCaribbean and Latin America

Leon H. Liege1 and Charles R. Venator

CHAPTER 1

I. INTRODUCTION

Forest nursery stock is produced by bare-root andcontainer systems. Healthy seedlings are grown ineither system if proper nursery management andtechniques are used (fig. l-1). Each system has twolevels of operation: 1) the traditional way, which issmall-scale and usually hand-labor oriented, and 2)the more modern way, which is large-scale and highlymechanized. Level of mechanization in either systemdepends on available human and monetary resourcesand the actual number of seedlings that will beplanted.

1.1 Purpose and Scope

This technical guide’ is a comprehensive summaryof forest nursery practices for the Caribbean, tropicalLatin America, and, to a lesser degree, other tropicalareas in the world. Included are actual and the au-thors’ recommended practices, pointing out the ad-vantages and disadvantages wherever possible withspecific examples. Container and bare-root systemsare discussed since both are used in the region, some-times interchangeably within individual countries.However, guides for vegetative propagation tech-niques are excluded, except for passing reference insome sections.

The intent is to make the guide self-contained. In-cluded are both traditional and modern approaches,with as many mechanical alternatives as possible.However, specific guides, such as fertilizer rates or

‘Funding for secretarial support was obtained from the U.S.Agency for International Development, project AIDISCYEZI06:Growth and Site Relationships of Caribbean Pine. .in Costa Rica,Jamaica, Trinidad, and Venezuela, 1982-87.

herbicide rates, are difficult to prescribe because eachcountry has its own problems with product availabil-ity and distribution.

1.2 Audience

The guide is technical because it is assumed thatthe readers are individual nursery managers or ad-ministrators who already have a graduate degree inforestry, agriculture, agronomy, crop science, or a re-lated discipline and have practical nursery experi-ence, at least in their own countries. Thus, all discus-sions are fairly detailed. More generalized guides arefound in Chapter 7 of the Peace Corps Tropical Amer-ica Reforestation Manual, now under editorial re-view. Definitions for pesticide (herbicide and insecti-cide) and other technical terminology are given inappropriate appendices or within individual chapters.

1.3 Subject Arrangement

This guide is divided into six major areas: 1) gen-eral stage setting for situations in the region, past andpresent, 2) overall nursery establishment and plan-ning, 3) seed management, 4) small-scale (traditional)operations, 5) general management considerations,and 6) large-scale operations. Where subject overlapoccurs within major sections, it is so indicated withinparentheses.

Since each chapter is an individual unit, literaturecitations are placed after each chapter. For certaintopics, more specific or “how-to-do-it” guides are givenin various appendices. Rather than order these con-secutively by numbering or lettering systems, a num-bering system was chosen that refers to actual chap-ters where a topic is discussed in greatest detail orwhere it appeared first. For example, the first Ap-pendix is number 4, because shading and nursery bedorientation are first discussed in Chapter 4.

Some subject matter overlap within chapters wasintentional. For example, weeding and watering arecritical concerns for early and later tending care of

Leon H. Liege1 was research soil scientist at the Institute of Tropical Forestry, Forest Service-USDA, Southern Forest Experiment Station, CallBox 25000, Rio Piedras, PR 00928-2500, and is now at the Pacific Northwest Forest and Range Experiment Station, Forest Service-USDA,Corvallis, Oregon. Charles R. Venator was plant physiologist at the Institute of Tropical Forestry and is currently forestry advisor to Mexico,USDA/Forest Service, U.S. Embassy/Mexico City, P.O. Box 3087, Laredo, Texas.

1

C O N T A I N E R

2 - FILL3-PLACE IN BEDS

1 -OBTAIN SOIL

4 - A - S O W INTRAY rL

f w~-CARE 8 T E N D

B-SOW DIRECT PRICK OUT (\ hPf - R E M O V E

6ONTAlNER JUST’ PRIOR TO

Y PLANTING

I -CULTIVATE 8 R A I S E

BED IN NURSERY

I ’

a,-

6 - PACK IN CARTONS/CRATES/BOXESFOR TRANSPORT

B A R E R O O T3 - C A R E B TEND SEEDLINGS

4 -UNDERCUT 8 SIDECUTROOTS TO CONDITIONSEEDLINGS; LIFT WHENREADY FOR PLANTING

Z-SOW SEEDS USUALLYOVER WHOLE BED

IN DRILLS

5 -DIP TO PROTECTROOTS FROM G-SEAL INDRYING OUT BAGS 8 KEEP

UNDER SHADE

Figure 1-l.-Container and bare-root nursery procedures. Adapted from (Il.

2

bath mechanized container and bare-root systems.However, severity of the problem and effective con-trols are slightly different for each system; thus, thesetopics are discussed separately in each chapter.

1.4 Terminology

The terms “container” and “pot” are used inter-changeably throughout the text. Both refer to indi-vidual or unitized entities containing some kind ofgrowing material to support seedlings. Detailedbreakdown of various pot or container types is givenin Chapters 9 and 15 and Appendix 15.

The terms “pot mix” and “pot medium” (“containermix” and “container medium”) are also used inter-changeably, which may not suit the precise technicalvocabulary of mechanized greenhouse operators. Yetboth terms are used throughout the region, reflectingthe usual practice of including more than one mate-rial in the growing medium.

“Plastic bag” is the shorter form of “polyethylenebag.” The first form is retained throughout, exceptwhere another kind of material is used instead ofpolyethylene.

1.5 Source Materials

Most practical examples and illustrations aredrawn from forest nursery experiences in Puerto Rico.Nursery research in Puerto Rico has been quite exten-sive because the United States has provided continualfinancial and personnel support for local reforestationefforts since the early 1900’s.

Included, whenever possible, are examples andpractices seen in the authors’ travels in the Caribbeanand Latin America or related by visitors and PeaceCorps workers in this region. Because local nurserymanagers travel little outside the region, appropriateliterature citations from nursery research done in theAsian and African tropics are included as well. Suchreferences are not comprehensive but indicate thewide range of practices and problems existing else-where. Frequently, these citations will indicate otherstudies that may be of interest to some readers.

1.6 Physical Setting

The difficulty in prescribing specific nursery prac-tices for individual countries is due in part to physicaldiversity in the countries themselves. The “tropics” isordinarily delineated as areas between the Tropic ofCancer and Tropic of Capricorn. This area is large andincludes geologically young, coastal plain soils; olderdissected and eroded uplands; and steep mountainranges having young volcanic soils. Climates may bevery dry, almost desertic, to moist and very wet, allwithin relatively short distances (e.g., going from 700

to over 5,000 mm of rainfall annually within a hori-zontal distance of 185 km in Puerto Rico). Culturalvalues, traditions, and standards of living varygreatly as well.

As a result, the geological-soil-climatic-culturalmix of tropical countries is highly diverse and unique;generalizations are often difficult to make and sup-port. For native workers and long-term residents oftropical regions, such diversity is normal and com-monplace. When such diversity is overlooked, how-ever, reforestation and nursery failures frequentlyoccur because localized conditions do not meet ideal-ized misconceptions of what tropical conditions reallyare. The authors have attempted to avoid over-generalizations and misconceptions in this guide.

1.7 Dedication

This guide is dedicated to nursery managers andadministrators throughout the Caribbean and LatinAmerica. The authors hope that it offers them newideas and alternatives for better utilization and moreefficient use of their country’s inherent natural,human, monetary, cultural, and social resources, bothfor short- and long-term planning.

LITERATURE CITED

1. Evans, J. Plantation forestry in theford: Clarendon Press; 1982. 472 p.

tropics. Ox-

CHAPTER 2

2. REVIEW OF REGIONAL NURSERYPRACTICES

2.1 Puerto Rico

2.1 .l Traditional Approaches.- Designation of theLuquillo National Forest by President Theodore Roo-sevelt on January 17, 1903, signaled the beginning ofa professional forestry program in Puerto Rico (19 1. In1917, the U.S. Department of Agriculture (USDA)Forest Service was incorporated into the Puerto RicoDepartment of Agriculture and Works. In 1920, theUniversity of Puerto Rico granted a small parcel ofland in Rio Piedras for the first forest tree seedlingnursery.

In its first year of operation, the nursery distributed3,800 tree seedlings at no charge (2). Demand forseedlings increased so rapidly that by 1925 over

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40,000 seedlings were distributed in 1 month alone.‘I’his total included 9,577 coffee seedlings. Shade treeseedlings for coffee plantations were also a significantpart of the nursery’s total production.

In 1926, a second forest nursery was constructed inUtuado; it produced coffee and shade tree seedlings. Athird forestry nursery was established at the Poly-technical Institute campus in San German in 1927; itproduced seedlings for private farms in westernPuerto Rico. In 1928, the three nurseries distributeda total of 860,000 seedlings.

In 1934, tree distribution to private farms was putunder control of the USDA Agriculture ExtensionService. In 1936, a large model reforestation projectwas established on a private farm. This “Mercado pro-ject” marked a new direction for reforestation inPuerto Rico. Approximately 20 percent, of the 7 mil-lion trees distributed went to private farms. Of these,60 percent were considered commercial species (2).

2.1.2 Nursery Consolidation.-Forest tree nurseryconstruction continued at a rapid pace. By 1940, 25small nurseries existed (2 1, primarily on state forests.Then, in 1945, two centralized nurseries were built,one in the Luquillo National Forest at Catalina (fig.2-l) and the other at Toa Alta. All small nurserieswere eliminated.

During the Civilian Conservation Corps era andafterwards, Federal funds helped plant some 10,000ha between 1934 and 1954. However, between 1954and 1963 only 720 ha were planted (27). The numberof trees planted per hectare generally ranged from1,700 to 2,950.

The decline in forest tree seedling production, be-ginning in the 1950’s and continuing until thepresent, had its roots in two different areas. First, treeplanting until 1954 was done on degraded and defor-ested land acquired by the Puerto Rican governmentand set aside as public forests. By the mid-1950’s,about 50 percent of this total area had been reforestedby direct. seeding with maria (Callophyllum brasilen-sis ) and roble (Tabebuia sp.) seedlings or other speciesnot suited for direct seeding. Second, private landsreforested in this period were usually large blocksabandoned from sugar cane plantations and coffee ha-ciendas or lands acquired by consolidating smallfarms. By 1954, these areas were largely reforested tothe extent desired by owners. The largest percentageof Puerto Rico remaining unforested in the 1950’s be-longed to small landowners who saw few economicrewards in reforestation.

In summary, the first quarter-century of nurserywork in Puerto Rico was characterized by: 1) highdependence on hand labor techniques; 2) production ofa very heterogeneous species mix of mostly hardwoods(e.g., about 75 species were used); 3) dependency uponU.S. Federal Government funds; 4) neglect of re-search; 5) exclusion of conifers except for a few Arau-

4

carias; 6) emphasis on producing coffee and coffeeshade tree seedlings; and 7) emphasis on commercialspecies like mahogany G’wietenia sp.), eucalyptus,cordia (Cordia sp.), Spanish cedar (Cedrela odorata),teak (Tectona grandis ), maria, and mahoe (Hibiscuselatus).

2.1.3 Nursery Centralization.-Seedling produc-tion took on a new dimension in Puerto Rico whennursery operations for the entire Island were consoli-dated at Monterrey, southwest of Dorado, in 1963 (fig.2-2A). The nursery was located on a flat coastal plainsite having ample room for expansion. Improvementfor consolidating forest seedling production was paidin part with Federal funds.

Nursery production at Monterrey concentrated onthose species showing superior growth and perform-ance in the late 1950’s and early 1960’s: Honduraspine (Pinus caribaea var. hondurensis), kadam (An-thocephalus chinensis), hybrid mahogany (Swieteniamacrophylla x S. mahagoni), and mahoe. Operationswere labor intensive, with all seedlings produced in10 by 25 cm vented plastic bags.

In 1975, to increase pine seedling production, a con-tainerized nursery operation (see Chap. 15) for Hon-duras pine was established in Santa Ana, near VegaAlta. The intention was to separate forest treeseedling production from fruit tree production, whichwas also centered at Monterrey. Unfortunately, thisproject was abandoned in 1979. Annual productionbetween 1976 and 1979 averaged about 300,000seedlings that were grown in Styrofoam block contain-ers.

Forest seedlings are now produced at Monterrey bythe local Administration for Agricultural Promotionand Development (AFDA) for the Forestry Area of thePuerto Rico Department of Natural Resources (DNR).Plans were underway to increase pine seedling pro-duction to 2 million annually by 1984 (fig. 2-2B),using Styroblock and plastic bag stock. The DNRmaintains its own small nursery on the CambalacheState Forest for mahogany, teak, and othbr hard-woods (fig. 2-3). During 1980-82, an average of500,000 and 100,000 seedlings were distributed annu-ally from the Monterrey and Cambalache nurseries,respectively.

2.1.4 The Catalina Nursery.- Bare-root ma-hogany seedlings are still produced at the Catalinanursery (fig. 2-1B). They are used in line plantings toupgrade understocked natural forest lands within theCaribbean National Forest. During 1982-85, produc-tion averaged 25,000 seedlings per year.

2.1.5 The ExperimentalNursery.-The Institute ofTropical Forestry (ITF) has maintained an experi-mental nursery in Rio Piedras for almost half a cen-tury (fig. 2-4A). Investigations from 1939 through the1950’s involved finding correct germination proce-dures and seed extraction and storage techniques (10,

Figure 2-l.-The ~am~n~~~vursery. ,n, room JJSJ M IYCW L I WUY “II.2 “, IW” ccI*II VI ,I”,, ucr *co b,I 1 UC, G”producing forest tree seedlings for the entire Island. fB) Today (19861 the nursery producesbare-root mahogany seedlings exclusively for line plantings to upgmde nntltrnl foroat lands--- ._- _I.-_ ,-. _-” “ .within the Caribbean National Forest.

5

Figure 2-2.-The Monterrey nursery in Puerto Rico. (A) As it appeared in the mid-1960’s. (B) As itappeared in 1985.

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Figure 2-3.-The Puerto Rico Department of Naturat Resources Forest Division nursery at Cambalache StateForest. (Al Unshaded outdoor beds. (BI Beds where different shading intensities can be used.

7

Figure 2-4.-The institute of Tropical Forestry (ITF) experimental nursery, Rio Piedras, PuertoRico. (A) Overall view of facilities, 1970’s through 1984; bare-root and mised-bench container beds (center); open-sided, covered work area (top); small bedsirrigated from below (bottom, right); and central irrigation pump house (center,right). (B) Several container systems that were tested in the mid-19705 for Pinuscaribaea and P. oocarpa provenances: Styroblocks, book planters, and polypots, inaddition to the traditional plastic bag.

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15, 16) for hardwoods and conifers tested in island-wide adaptability trials (I 7,18). This early work suc-cessfully attributed poor pine growth across the Is-land to lack of native mycorrhizal fungi (3).

From the 1960’s through 1978, ITF nursery re-search included germination tests and observationson seedlings used for small field trials of kadam andGmelina provenances (C.R. Venator, unpublished ma-terials at ITF); a local pine seed orchard (71; and inter-national trials of mahogany (22,25 1, teak (4,24 >, andP. caribaea and P. oocarpa (28,29,30). Research onpines included suitability of bare-root (2) andcontainer-grown stock (fig. 2-4B) (32 ). Survival impli-cations of speed of germination, hypocotyl color andchlorophyll-a content, and emergence time of second-ary needles were shown for P. caribaea varieties. (33 1Albino or other “abnormal” seedlings were also re-ported (28 ).

Today, ITF has no ongoing nursery research pro-gram as it did from 1969 to 1978. Since 1979, only afew hundred to 1,000 or 2,000 seedlings have beenproduced annually. The facilities are used for summerstudent and thesis projects (6, 26) and short coursetraining exercises (II ). A small seed bank is stillmaintained for storing and distributing seeds to othergovernmental agencies for nursery research.

2.2 The Caribbean and Tropical Americas

2.2.1 Traditional Approaches.-Traditional nurs-ery practices in Caribbean and Tropical nations aregenerally similar. Operations are labor intensive andsmall-scale. Forest Department or Forest Divisionstaff manage the nurseries. The same staff providestechnical assistance on where and how to plantseedlings that are usually provided at no cost (I, 27).Most seedlings are used to reforest blocks of land that,once cut over for agriculture, are now idle or aban-doned. Small landowners clear and plant severalacres each year on private lands, and governmentworkers plant crownlands (21,231. Sometimes farm-ers receive cash incentives for tree planting.

Most countries have at least one small but perma-nent regional nursery that annually produces 10,000to 30,000 seedlings of several species. In a large coun-try like Jamaica, a regional nursery may produce500,000 to 1 million or more seedlings per year. Onsmall West Indies islands, temporary “flying” nurs-eries are established for special projects on local ero-sion control and improvement of understocked forests.Young seedlings are brought in from a regional nurs-ery and grow to outplanting size under temporaryshade, sometimes one large tree (fig. 9-3). Or, insteadof using germinated seedlings, naturally regeneratedseedlings (i.e., “wildings”) located close to the flyingnursery are dug up, transplanted into pots, and areleft to grow to outplant size.

Agroforestry plantings are common when farmersinterplant trees with food crops. When cultivationstops, the small tree crop remains. In Haiti, wherepopulation density is high, land is scarce, and fuel-wood is even scarcer, seedlings are given to or boughtby farmers who tend them in small parcels with foodcrops (14). After 2 or 3 years, the fast-growing treesare cut for fuelwood or charcoal; some trees may beleft for post and pole production.

The most common problem in traditional reforesta-tion practices is failure to plant seedlings immedi-ately after obtaining them. If seedlings are notwatered and protected from the sun or desiccatingwinds, they will all die before or shortly after plant-ing. Nursery stock in large containers can withstandharsher conditions than stock in small containerswhen delivered seedlings are not planted immedi-ately. However, when large containers are used, fewerseedlings are delivered to each landowner. Pines andeucalyptus are generally produced in containers.

Using bare-root and stump nursery stock elimi-nates cumbersome containers and allows easier dis-tribution of larger numbers of seedlings to individuallandowners (20 ). Not all species are plantable as bare-root or stump stock. Commonly planted bare-rootstock are mahogany and Gmelina; teak and Gmelinaare also planted as stumps (fig. ll-5B).

Two well-known traditional container productionsystems are those using tarpaper pots (34 1 and plasticbags (31). The somewhat mechanized tarpaper potsystem was developed in Surinam and was adaptedlater by several countries. Major drawbacks of tar-paper plots now are cost and availability of tarpaper.For small and highly organized reforestation projectswhere tarpaper is readily available, the tarpaper potsystem may work well.

The plastic bag system is widely used in American,Asian, and African countries. Clear and dark plasticare available, with small (400 cc) to large volume(~3,000 cc) capacities. Bags are usually filled withalluvial soil. In Puerto Rico, Trinidad, and Jamaica,sugarcane waste (bagasse), rice hulls, vermiculite,and peat moss are mixed with soil or compost withoutsoil.

Each country, and regional nursery within a coun-try, follows different practices for tending seedlings,including shading and applying fertilizers. Specificexamples are given in appropriate chapters of thisguide.

The biggest difference between traditional nurserypractices in Caribbean and Tropical American coun-tries is the type of container used to propagateseedlings. Common methods in any country depend onpast traditions and customs as well as local organiza-tion of seedling distribution and planting efforts. Themajor goal is to produce seedlings that can surviverigors of small scale operations, Highly efficient and

9

Figure 2-5.-Large-scale, bare-root seedling production of Caribbean pine (P. earibaea var. hon-

durensis) by CONARE (Compariia National de Reforestation) in Venezuela’s easternsavannas .

cost saving techniques are available to nursery man-agers, but sometimes these conflict with other over-riding community goals of providing employment.

2.2.2 Nontraditional Approaches-Large coun-tries with rising demands for wood products cannotobtain adequate numbers of seedlings for reforesta-tion projects from small traditional nurseries. In-stead, large-scale, semi- and fully-mechanized opera-tions at large central nurseries produce millions ofseedlings annually. Examples are Carton de Colom-bia’s hardwood and pine plantings in Colombia’s high-lands (12,13 1, CONARE’s (5 1 operations in the east-ern savannas of Venezuela with P. caribaea var.hondurensis and eucalyptus (fig. 2-5), and the JAR1project’s work (8, 9) in the Brazilian Amazon Basinwith P. caribaea var. hondurensis, Gmelina arborea,and eucalyptus. In 1983, production was 30 millionseedlings at three CONARE nurseries, each produc-ing 10 million.

In large-scale operations, seeding, tending, lifting,and outplanting activities are highly organized. Highoutplant survivals require same-day planting ofseedlings after lifting and transporting them to thefield. Large-scale seedling production is suitable forboth bare-root (CONARE-Venezuela) and container-ized (Carton de Colombia-Colombia) nursery stock.Stump plantings were initially used for Gmelina atJAR1 in Brazil; yearly production once approached1,000 ha and 1.3 million stumps. Before takeover bylocal Brazilian businesses in 1982, JAR1 field opera-

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tions for Gmelina had changed to operational directseeding on 500 ha.

Nontraditional, large-scale nursery operations forseeding, tending, and fertilizing are quite variablefrom country to country. Practices used depend onspecies planted (hardwoods versus conifers), soils(sands versus volcanic ash), local climate (dry versusmoist or wet), and outplanting technique (machines orby hand). Some of these large-scale practices are ex-plained in detail in Chapters 15 and 16.

LITERATURE CITED

1. Anonimo. Repoblacion forestal y frutal en Cubasocialista, Informe 1962. Departamento Fore-stal y Frutal, Instituto National de ReformaAgraria. La Habana, Cuba; 1962. 94 p.

2. Bague, J. Presencia do 10s montes en nuestra his-toria-Apuntes conjuntivos. Rev. de Agricul-tura de Puerto Rico. 49(l): 4-77; 1962.

3. Briscoe, Charles B. Early results of mycorrhizalinoculation of pine in Puerto Rico. CaribbeanForester. 20(3-4): 73-77; 1959.

4. Briscoe, C. B.; Nobles, R. W. Effects of pruningteak. Res. Note ITF-11. Rio Piedras, PR: U.S.Department of Agriculture, Forest Service, In-stitute of Tropical Forestry; 1966. 5 p.

5. CONARE. (Compania National de Reforesta-cion). Algunas consideraciones de politica fore-

stal relatives a las plantaciones forestales ybosques de production. Venezuela Forestal. 6:12-37; 1982.

6. Garcia, Aileen. Propagation sexual y asexual deSwietenia macrophylla. Rio Piedras, PR: U.S.Department of Agriculture, Forest Service,Southern Forest Experiment Station, Instituteof Tropical Forestry; 1981. 27 p.

7. Geary, T. F.; Felix de Barros, Nairam. Seed cropenvironment may influence progeny tests.Commonwealth Forestry Review. 52(2): 160-162; 1973.

8. Hartshorn, Gary S. GSH-12: JARI. Hanover, NH:Institute of Current World Affairs; 1979. 20 p.

9. Hartshorn, Gary S. GSH-19: JAR1 II. Hanover,NH: Institute of Current World Affairs; 1981.11 p.

10. Holdridge, L. R. A rapid method of extractingbalsa seed. Caribbean Forester. l(2): 25; 1940.

11. Institute of Tropical Forestry. Research unit sum-mary, Fiscal Year 1983. Rio Piedras, PR: U.S.Department of Agriculture, Forest Service,Southern Forest Experiment Station, Instituteof Tropical Forestry; 1983. 14 p.

12. Ladrach, William E. Paneles de tubos: un metodopara producir arboles en viveros. Informe deInvestigation Forestal 18. Carton de Colombia,S.A. Cali, Colombia; 1977. 8 p.

13. Ladrach, William E. Nursery tests with new con-tainers for the production of seedlings. ForestryResearch Report 17. Carton de Colombia, S.A.Cali, Colombia; 1977. 12 p.

14. Liegel, Leon H. Final report: Soil and site assess-ment for USAID/Haiti Agroforestry OutreachProject in the Cul-de-Sac Plain and other se-lected areas; 1982 August 22-September 5; RioPiedras, PR: U.S. Department of Agriculture,Forest Service, Southern Forest ExperimentStation, Institute of Tropical Forestry; 1983.38 p.

15. Marrero, Jose. A seed storage study of maga.Caribbean Forester. 3(4): 173-184; 1942.

16. Mar&-o, Jose. Tree seed data from Puerto Rico.Caribbean Forester. 10: 11-36; 1949.

17. Marrero, Jose. Reforestation of degraded lands inPuerto Rico. Caribbean Forester. 11(l): 3-15;1950.

18. Marrero, Jose. Results of forest planting in theInsular Forests of Puerto Rico. CaribbeanForester. ll(3): 107-147; 1950.

19. Murphy, L. S. Forests of Puerto Rico. Agric. Bull.354. Washington, DC: U.S. Department ofAgriculture; 1916. 100 p.

20. Napier, Ian. La poda de raiz de1 Pinus oocarpa yPinus caribaea en 10s viveros de Honduras. Es-cuela National de Ciencias Forestales, Corpo-ration Hondurena de Desarrollo Forestal. Ar-ticulo Cientifico 5. Siguatepeque; 1982. 15 p.

21. Niepagen, Carlos E. Practicas recomendables enviveros de coniferas para la Provincia de Tu-cuman. Circular 172. Section Estudios Fore-stales, Estacion Experimental Agricola de Tu-cuman. San Miguel, Argentina; 1964. 10 p.

22. Nobles, R. W.; Briscoe, C. B. Height growth ofmahogany seedlings. Res. Note ITF-6. RioPiedras, PR: U.S. Department of Agriculture,Forest Service, Institute of Tropical Forestry;1966. 3 p.

23. Nobles, R. W.; Briscoe, C. B. Killing unwantedWest Indies mahogany trees by peeling andfrilling. Res. Note ITF-8. Rio Piedras, PR: U.S.Department of Agriculture, Forest Service, In-stitute of Tropical Forestry; 1966. 3 p.

24. Nobles, R. W.; Briscoe, C. B. Mowing understoryvegetation in a young teak plantation. Res.Note ITF-9. Rio Piedras, PR: U.S. Departmentof Agriculture, Forest Service, Institute ofTropical Forestry; 1966. 2 p.

25. Nobles, R. W.; Briscoe, C. B. Root pruning of ma-hogany nursery stock. Res. Note ITF-7. RioPiedras, PR: U.S. Department of Agriculture,Forest Service, Institute of Tropical Forestry;1966. 4 p.

26. Rivera, Sheilla. Propagation de semilla de Swi-etenia macrophylla King utilizandotratamiento mecanico. Rio Piedras, PR: U.S.Department of Agriculture, Forest Service,Southern Forest Experiment Station, Instituteof Tropical Forestry; 1982. Rep. 8 p.

27. Rodriguez-Vidal, J. A. Viveros forestales. Rev. deAgricultura de Puerto Rico. 49(l): 156-164;1962.

28. Venator, C. R. An abnormal short primary needleform of Pinus caribaea var. hondurensis. In:Burley, J.; Nikles, D. G., eds. Tropical prove-nance and progeny research and internationalcooperation; October 1973; Nairobi, Kenya;IUFRO Working Parties S2.02.08, S2.03.1;1973: 322-326.

29. Venator, C. R. International provenance trials ofPinus caribaea and P. oocarpa in Puerto Rico.In: J. Burley; Nikles, D. G., eds. Tropical prove-nance and progeny research and internationalcooperation; October 1973; Nairobi, Kenya;IUFRO Working Parties S2.02.8, S2.03.1; 1973:26-28, 95-96.

30. Venator, C. R. The relationship between seedlingheight ,and date of germination in Pinus carib-aea var. hondurensis. Turrialba. 23(4): 473-474; 1973.

31. Venator, C. R.; Liegel, Leon H. Manual de viverosmecanizados para plantas a raiz desnuda; y,sistema semimecanizado con recipientes de vol-umenes menor a 130 cc. Agencia para el De-sarrollo International de 10s Estados Unidos yMinisterio de Agricultura y Ganaderia, Pro-

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grama National Forestal. Quito, Ecuador;1985. 212 p.

32. Venator, C. R.; Rodriguez A. Using Styroblockcontainers to grow Pinus caribaea var. hon-durensis Barr. & Golf. nursery seedlings. Tur-rialba. 27(4): 393-396; 1977.

33. Venator, C. R.; Howes, C. D.; Telek L. Chloro-phyll and carotenoid contents of Pinus caribaeaseedlings and inferences for adaptability. Tur-rialba. 27(2): 169-173; 1977.

34. Voorhoeve, A. G.; Weelderen, A.W.H. Nurserypractice of Pinus caribaea. Surinam Forest Ser-vice, Research Branch. Paramaribo; 1968.20 p.

35. Whitmore, J. L. Cedrela provenance trial inPuerto Rico and St. Croix: nursery phase as-sessment. Turrialba. 21(3): 343-349; 1971.

CHAPTER 3

3. NURSERY SITE SELECTION

Nursery site selection is done with considerablecare and caution. Many ecological and economic fac-tors influence the success or failure of a nursery. Asminimum requirements, each nursery site must havesufficient area, suitable climate and soils, adequateenergy and transportation facilities, water of ade-quate quantity and quality, and available labor toproduce healthy seedlings. Some factors discussed forsite selection may not be important if a nontraditionalmechanized system (Chap. 161, rather than either atraditional container or bare-root system, is chosenfor operational use.

3.1 Climate and Environment

Preferred sites are those with favorable climaticand environmental conditions that are neither too wetnor too dry. Long-term rainfall and temperature datawill indicate whether normal rainfall is adequate forgrowing seedlings. Windy areas should be avoided tominimize windburn and desiccation effects onseedlings. Constant whipping of seedlings by wind isdetrimental to growth. In the dry season, plants areoften watered daily to avoid desiccation, particularlyyoung seedlings or those recently transplanted. Expe-rience in Puerto Rico shows that dry, gusty, Februaryand March winds will desiccate young pine seedlingsless than 4 weeks old if they are not watered suffi-ciently. Locating nurseries in the Caribbean between90 and 300 m above sea level and well away from

12

coastal areas will avoid wind-laden salt contamina-tion.

On islands like Puerto Rico where predominanttrade winds move from east/southeast to west/north-west, nurseries are best located on west or northwestslopes if flat protected valleys are unavailable. A westor northwest aspect provides greatest protection fromwind, lowers evapotranspiration and creates more hu-midity among seedbeds.

When environmental alternatives exist for estab-lishing forest nurseries, extremely dry areas, such asthe southwestern coast of Puerto Rico, should beavoided. Dry climates are unfavorable for fast-growing species like pine, eucalyptus, kadam, cedar,mahogany, and Gmelina. The number of shade-freedays in dry, semi-desert areas is also high, increasingtranspirational water loss from seedbeds. The bestnursery location in Puerto Rico is in the interiormountain range, which has the greatest number ofdays in which rainfall exceeds 2.5 mm (8). Major se-lection criteria for nursery managers in countrieswith predominantly dry climates (Haiti, DominicanRepublic) are adequate sources of irrigation waterand soils of low salt content.

3.2 Location and Essential Facilities

Locating nurseries close to major reforestationareas assures timely transportation of seedlings fromnursery to field. Costs are reduced and fewer trucksare needed if seedling delivery trips are short. Thus,nurseries are usually located on major road systemsconnecting with planting areas. In Puerto Rico, theideal central nursery location is in the western part ofthe Island where the largest tracts of reforestableland are found. For large operations, staff personnelhousing on nursery grounds deters vandalism, createsstrong job identification, and facilitates wateringplants on long weekends or holidays.

Large, mechanized nurseries must have electricalpower sources to operate equipment such as irrigationpumps, refrigerators, potting machines, typewriters,and lighting systems. Heavy machinery, includingsoil mixers, potting or packing machines, and saws,may require three-phase electrical lines. These arecostly to install if no lines exist close to the nurserysite. For areas without power or where power outagesare frequent, a diesel-powered generator may be nec-essary.

Good communications are essential. If possible,nurseries should be located close to existing telephonelines or have radiotelephone communications be-tween nursery and central forestry administrative of-fices. Such systems help coordinate field deliveriesfrom the nursery headquarters. Regular mail serviceis needed to transmit seedling requests to the nurseryand to inform interested landowners of the availabil-ity of the nursery’s current stock and prices.

3.3 Soils and Topography

For drainage control, nursery beds should have a0.2 to 1.0 percent slope; crossbed slope for the entirenursery area can be 0 to 2.0 percent. Sites subject toflooding and having rocky soils should be avoided (fig.3-l). Soil scientists should be consulted throughoutthe entire site selection phase.

3.3.1 Physical Conditions.-For a containerizednursery, soil type may not be an important site factor.However, soil is very crucial in selecting bare-rootnursery sites because all drainage and trafficabilityproblems, as well as ease in lifting seedlings, are di-rectly or indirectly related to soil texture (I ). Selec-tion of a good nursery site must be based on soil sur-vey data and actual field visits, not on easy access or

SURFACE ROCKS PREVENT USE OFSMALL MACHINES 8 RESTRICT BEDCONSTRUCTION.

SUBSURFACE ROCKS OR “PANS”PROHIBIT GOOD ROOT PENETRATIONa MAY INDICATE ORAINAGE PkOBLEMS.

CRACKED SOIL INDICATES HIGH CLAYCONTENT 8 WATER SHORTAGE IN DRYPERIODS OR POOR DRAINAGE IN WETPERIODS

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L O W AR EAS a DRAINAGES AR E TooWET IN RAINY PERIODS. CHOOSEAREAS WITH SLIGHT SLOPES SOTHAT EXCESS RAIN DRAINS OFFSITE ADEQUATELY.

LOW WET A R E A ’

Figure 3-l.-Poor nursery sites. Adapted from (9).

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economic advantage. In fact, because nurseries arelong-term commitments, “sacrificing” the good physi-cal and chemical properties of soils for other site fac-tors such as closeness to paved roads or power lines isnot recommended. These factors can be added later,whereas it is impossible to move a nursery once bedsare contoured, water facilities are installed, and nurs-ery buildings are finished.

In all cases, clay soils with high shrink-swell capac-ity must be avoided (fig. 3-l). Clay soils are also unde-sirable for raising bare-root seedlings because bothlarge and small roots are broken during lifting (4,6).Aeration is also poor in heavy clay soils, inhibitingseedling root development.

Soils that range between fine sand and sandy loamhave the fewest problems related to soil texture. Theydo not readily compact as do clay soils. Other advan-tages of sandy soils are excellent drainage, fewer rootrot problems, water more readily available to plantroots, easy tillage and no crusting-over followingrains or irrigation, and suitability for heavy mechan-ical equipment used in constructing beds and main-taining healthy seedlings via various cultural activi-ties.

When the nursery is contoured, all topsoil should beremoved first and then replaced after grading is com-pleted. Lifting properties of nursery beds are quicklyaltered if A and B horizons are mixed during plowingand grading operations. All physcial and mechanicalanalyses of soils at a potential nursery site should bedone by a soil scientist on a well replicated basis(Chap. 14).

3.32 Chemical Conditions.-Soil acidity or reac-tion (pH) is probably the single most important chem-ical property of nursery soils. It directly affects otherchemical reactions in the soil, the behavior of seedlingroots, and soil micro-organisms around roots. Opti-mum pH varies according to the species grown. Fortropical pines, the range is usually pH 5.5 to 6.0; whenacidity drops below pH 5.0 or rises above pH 6.5, cor-rective action must be taken (21.

When soil becomes too acidic (below pH 5.01, lime(CaCO,+MgCO,) is added at rates usually rangingfrom 1 to 6 metric tons per ha. Actual amounts appliedto any site depend on change in acidity desired, soiltexture, and organic matter content. The kind of limeapplied depends on the amount of available calciumand magnesium in the soil. Dolomitic lime is added tosoils lacking both calcium and magnesium; calciticlime is added when only calcium is needed. Soils toohigh in calcium and magnesium can induce trace ele-ment deficiencies in woody species. Acid-forming fer-tilizers such as ammonium sulfate or ammonium ni-trate are added to lower high pH values (Chap. 13).

3.4 Water Supply

The lifeline of any nursery is the water supply. Toproduce seedlings that are ready for planting bybeginning of the wet season, seedling culture mustbegin at the end of the wet season and extend throughthe dry season. Unless sufficient water is available, aserious problem can develop. Even small islands canhave a wide variation in rainfall. For example, a nurs-ery located on the dry, south coast of Puerto Rico usu-ally has 260 to 300 rainless days or days with lessthan 0.25 mm of rain and only 30 to 40 days of 2.5 mmof rainfall (8). Also important are the number of wetversus dry months in each locality. A month is consid-ered dry if it receives less than 50.0 mm of rainfall.Generally, artificial watering systems must be able toprovide a minimum of 100 mm per month for conifersand 200 mm for hardwoods.

The water supply must be monitored on a regularbasis to determine whether it contains excess salts orpollutants. If neither can be removed or lowered toacceptable levels, a new water supply is needed. Wellwater may be used, but in coastal areas excessivewithdrawal may result in salt water intrusion to theaquifer. The ideal water source is a large pond orpollution free river from which water is pumped to anelevated tank and distributed under pressure througha sprinkling system. If a natural water source is un-available, then treated water from a public water-works can be used. However, proper authoritiesshould be consulted first to determine whether suffi-cient water is available. Also, the waterworks author-ity has the technical expertise to determine whethersufficient water pressure exists at the selected site forhigh-pressure irrigation systems.

Salts and calcium must be monitored in naturalwater sources. Increases in both may raise soil alka-linity that in turn favors growth of root rot organisms.Conifers are more sensitive to excess calcium thanbroadleaf tree species. When the potting medium ex-ceeds pH 7.0, conifers usually exhibit chlorosis be-cause soil iron becomes less available. Under alkalineconditions, young leaves often emerge yellow. Theproblem is intensified if a sodium or potassium nitratefertilizer is applied because potting medium alkalin-ity will increase even more. Soil or soil mixturesabove pH 6.5 are less favorable for mycorrhizal fungigrowth and tend to favor pathogenic fungi that causedamping-off.

3.5 Air

Air pollution is a potential problem for nurserieslocated close to highly industrialized areas or even in

14

rural areas. Phytotoxic pollutants, including sulfurdioxide (SOa), hydrogen fluoride (HF), and ozone (Osl,can be carried downwind from their source onto anursery and settle out directly on seedlings (3 ). Pollu-tants may also be carried great distances by wind andthen be deposited on seedling foliage and possiblycause seedling death.

3.6 Labor

Because nurseries require skilled and. unskilledlabor, they must be located close to cheap and avail-able labor sources. If laborers must be brought in fromfar away cities, housed, and fed in work camps, ex-penses will be very high. Therefore, it is better tolocate nurseries near towns or villages from whichlaborers can commute. Much nursery work is sea-sonal. Workers living nearby can supplement theirnursery income from other jobs in their villages or ontheir own small farms (7).

Where project funds are limited, contracting forsome production operations may be better than main-taining a permanent or seasonal labor force, particu-larly for traditional hand operations. Nurseries alsoemploy several kinds of skilled labor. Employees areneeded for applying pesticides or fertilizers, main-taining seed storage and germinating operations, andoperating heavy machines and tractors.

3.7 Nursery Equipment and Tools

Organization and layout of a nursery require spacefor storage and maintenance of equipment and tools(5). An adequate inventory system must be imple-mented from the very beginning of nursery opera-tions. If an inventory is not made and equipment notaccounted for, many tools will be either lost or stolenand purchased in duplicate when they cannot be lo-cated. Time and money are wasted when tools orequipment are not readily available. One personshould be given responsibility for equipment issue,retrieval, operation, maintenance, and repair.

A bimonthly maintenance and preventive mainte-nance schedule for major equipment should be imple-mented. For example, compost shredders, soil mixers,mechanical bag fillers, etc., should be greased regu-larly and covered to avoid dust accumulation duringstorage. When rust appears, equipment should besanded and repainted with rust-inhibiting paint. Inthe moist and wet tropics where deterioration of me-chanical devices is rapid, repainting schedules are fre-quent. In all climates, preventive maintenance is theonly way to prolong the life and use of nursery equip-ment.

An equipment inventory should be taken immedi-ately after the planting season has ended or at theearliest appropriate time thereafter. Thus, the nurs-ery manager will know well ahead of time when to

purchase equipment or supplies for the next season.Some of the basic tools and equipment needed for a

tropical nursery are listed below. The list may not beexhaustive for certain specialty nurseries; however,smaller traditional nurseries in developing countriescan accomplish much with only a few of the itemslisted. -

Adding machineAdzeAnemometerApron, clothApron, rubberAuger, soil typeAutoclave, pressure

cooker type, woodenand rubber

Balance, analyticalBalance, barBalance, spring typeBaskets, metalBaskets, wovenBench, sittingBinocularsBlackboardBoots, rubberBoxes, wooden bottomBoxes, wire mesh bottomBuckets, galvanizedBuckets, plasticBurlap, bags and rollsCans, gasolineCans, wateringCarpenter supplies and

toolsChain sawCloth bagsContainers, large capac-

ity measuringContainers, polyethyleneContainers, tinCrowbarCutters, wireDesk lampsDrafting suppliesDrilling, electric, plus

bitsDrums, 20%liter, severalElectronic calculatorElectric bag sealerElectric fanElectric grinderFilesFilter paper, for seed ger-

minationFire extinguisherFirst aid cabinetFlats. galvanizedI”

Forklift

Rasps, wood

Freezer, for seed storageFunnelsGerminatorGloves, clothGloves, rubberGoggles, industrial typeGraduated cylindersGrafting tapeHacksaw and bladesHammersHammer mill, large ca-

pacityHand cartHand lens, 10xHormone for vegetative

propagationHygrothermograph,

recordingKnives, graftingKnives, pruningLabels, dagger typeLabels, plastic slip-onLaboratory chemicals

and glasswareMachetesMalletsMasks, respiratoryMetalworking equipmentMicroscopeMirrorMixer, soilNails, galvanizedNozzles, fogg-it typeOffice supplies and

equipmentPetri dishespH meter, electronic and

portablePickaxePitchforksPlastic trays, for seed

germinationPliersPolyethylene bagsPolyethylene sheeting,

blackRakes, gardenRain guage station

15

RefrigeratorsRulers, metricSaran shade, 20, 30, and

50 percentSaw, electricScrewdriversSeed blowerSeed dividerSeed moisture testerSeed separatorSeed sieveShovelsShredder, for compostSide cuttersSoil moisture testerSoil sieves, large capac-

itySoil sterilizerSoil thermometer

Soldering equipmentSpray tanks, 11-liter, for

fertilizer and pesticidesStakes, wooden, treatedStorage binsTables, wooden or metalTape measuresTest tubesThermometers, recordingTractorsViseWagonsWelding equipmentWheel barrowsWire, galvanizedWire mesh, 6-mm & 13-

mm sizesWrenches, plumbing type

LITERATURE CITED

1. Brady, Nyle C. The nature and properties of soils.8th ed. New York: Macmillan; 1974. 639 p.

2. Davey, C. B. Seed orchard soil management. In:Tree improvement short course. Raleigh, NC:School of Forest Resources, North Carolina StateUniversity; 1977: 84-89.

3. Davidson, H.; Mecklenburg, R. Nursery manage-ment administration and culture. EnglewoodCliffs, NJ: Prentice Hall, Inc; 1981. 450 p.

4. Fielding, J. M. Factors affecting the rooting andgrowth of Pinus radiata cuttings in the opennursery. Forestry and Timber Bur. Bull. 45.Canberra: Commonwealth of Australia, Dep. ofNational Development; 1969. 38 p.

5. Galloway, Glen. Guia para el establecimiento ymantenimiento de un pequeno vivero forestal.Informe de Investigation Forestal 72. Carton deColombia, S.A.: Cali, Colombia; 1981. 11 p.

6. Minko, G.; Craig, F. G. Radiata pine nursery re-search in North-Eastern Victoria. Forests Com-mission Bull. 23. Melbourne, Australia; 1976.24 p.

7. Paul, Derek K. A handbook of nursery practice forPinus caribaea var. hondurensis and otherconifers in West Malaysia. United Nations De-velopment Programme, Food and AgricultureOrganization of the United Nations FO:SF/MAL12, Working Paper 19. Kuala Lumpur,Malaysia; 1972. 139 p.

8. U.S. Department of Commerce. Climates of PuertoRico and U.S. Virgin Islands. Climatography ofthe United States 60-52. Washington, DC: 1970rev. 29 p.

16

9. Weber, F. R. Reforestation in arid lands. PeaceCorps/Vita Publications Manual Series 37E.Washington, DC: Government Printing Office1977. 248 p.

CHAPTER 4

4. DESIGN AND LAYOUT

A permanent nursery is a long-term commitmentand investment. As much care and caution should beused in designing a nursery as in choosing a site.Foresight in design and layout will increase efficiencyin growing seedlings and in minimizing lost time forpersonnel.

Actual design and layout depend on whether anursery produces bare-root or containerized seed-lings, uses mechanized or nonmechanized techniques,and has a large or small capacity. Anticipated opera-tion as a commercial ornamental (2) or commercialgreenhouse (6) is also a concern.

4.1 Production Areas

Nursery production areas are dedicated to actualgrowing of seedlings, whether in mounded or ground-level bare-root beds, raised or ground-level containeryards, or germination and propagation plant shelters.In small traditional nurseries, production areas makeup 90 percent or more of the total nursery area (fig.4-l). In large bare-root nurseries, as much as 50 per-cent of the production area may be left fallow eachyear (Sec. 16.1.2).

Production efficiency is achieved by locating eachmajor operation in a specific area of the nursery.Within each area, fallow or unused beds may existfrom year to year. In large operations, areas shouldinclude space for expansion. Bare-root beds are al-ways located in those areas having the best soil chem-ical and physical properties.

Production area size depends on several factors.General considerations are size of entire complex, ex-pected yearly production rates for species grown,seedling density in beds, kind of equipment used, andwhether bed orientation is square, or rectangular andparallel, or diagonal to major buildings (2, 3). Forbare-root beds, specific considerations include thenumber of rows in each bed, seedling spacing in eachrow, and minimum aisle width needed to accommo-date equipment or hand labor. For container beds,

0 O R OROUNOL E V E L OEDS

Figure 4-I.-Generalized design and layout of a small traditional nursery. Most of the area isproduction oriented because operational, storage, utility, and communication areasare minimal. Adapted from (7).

specific considerations are whether beds are raised orground-level type, have hard or soft surfaces, havewide or narrow benches, and whether containers usedare unitized or individual cells (figs. 15-1 and 15-6).

4.2 Administrative/Employee Areas

These areas should be located close to major accessroads. Routine movement of personnel and vehiclesshould not disrupt other operations (5). For example,separate internal access roads for employee, delivery,and machine traffic are possible, as are separate facil-ity entrances for field workers and visitors. Separa-tion of administrative and nursery worker facilities(change areas, rest rooms, etc.) is another alternative.Certain common areas for parking, recreation, andmeals provide opportunity for interaction betweennursery workers and administrative personnel aboutmutual interests and problems.

Scale of operation dictates need for special facilities.Large nurseries have residence areas and an infir-mary; a part-time nurse or doctor may be on call cer-tain days or daily. Such facilities should be close to,but separate from, other buildings to ensure the pri-vacy and well-being of persons needing them.

4.3 Storage-Shipping-Receiving Areas

These areas are the hub of most nurseries becausethey receive all raw materials for producing nurserystock. Access roads should be wide, all-weather type,and free of curves (fig. 4-2). Turn-around areas areneeded for trucks entering and leaving the facilities.

Storage facilities must be large enough to accommo-date daily raw material needs as well as spare partsfor small equipment (grinders, power saws, mowers,etc.). Machine sheds and work areas for servicingheavy equipment are best located away from mainfacilities.

4.4 Operational Areas

Other areas are required for extracting, drying, andprocessing seed; preparing germination trays and potmix; screening compost; filling pots; and washing,grading, and packaging seedlings (7). The key con-cern for these areas is maintaining flexibility and in-tegrated flow of activities (1).

Flexibility’ means the willingness to incorporatenew machinery and procedures as needed to increaseproduction or to change kinds of seedlings grown. It isbest to overbuild new facilities to accommodate futureactivity shifts.

Integrated flow means arranging buildings, walk-ways, roadways, alleys, etc., to complement eachother. For example, compost pits should be close tocompost screening and mixing areas. Space is savedby intentionally designing certain areas to accommo-date several activities. Open-air seed drying areasalso serve for filling pots in good weather; covered,open-sided buildings double as lunchrooms and placeswhere small construction jobs (e.g., making germina-tion tray shade boxes) are possible in bad weather (fig.4-3).

4.5 Herbicide and Insecticide Storage

Chemical storage areas are specialized operationalareas because materials stored in them have toxic orcaustic properties. All chemicals, including insecti-cides, fungicides, and herbicides must be protectedfrom environmental elements. Suitable storage areasmust be:. located in separate buildings away from other areas

used by humans and animals;. constructed of fire-proof materials and hard-

surfaced shelves and floors;l accessed only by authorized personnel;. kept dry, cool, and well-ventilated; and. posted with proper signs advising of dangerous area

(fig. 4-4).

17

Figure 4-2.-Hard-surfaced, split-access road to nursery facilities of CONARE (Compariia Nationalde Reforestation), E&ado Monagas, in Venezuela’s eastern savannas, Right fork goes tolaboratory and administration area; left fork goes to employee residence, meal, andrecreation facilities. Not seen is a dirt road off left fork that leads to machine shop andstorage area.

Figure I-3.-Covered, open-sided nursery building that also doubles as lunchroom, seedextraction and drying area, and carpentry area for making small items suchas shade frames for germination trays.

1 8

Figure 4-4.-Pesticide and herbicide storage areas should be clearly marked, left dry, and kept lockedwhen not in use.

Insecticides and herbicides are always stored sepa-rately. All chemicals are stored in their original con-tainers to avoid confusion with other products. Con-tainer lids or caps are tightly closed to preventvolatilization of liquids and escape of toxic fumes. Ifleaks are found, cleanup of remaining material andwaste is done by following indicated label and stand-ard safety instructions, using safety equipment(masks, gloves, respirators) when needed. For certainhazardous materials, local authorities may have toauthorize final disposal. An up-to-date inventoryshould be kept of all chemicals, showing remainingamounts of liquid, solid, granular, and gaseous mate-rials. At least one supervisor and one worker shouldbe trained in all aspects of chemical use, storage, andhandling so that routine andare understood and practiced.

emergency procedures

4.6 Laboratory Facilities

Laboratory space is only essential for large nurs-eries. It provides a separate area to conduct pretreat-ment germination and storage experiments on seed,to test for soil pH and dissolved salts, and to monitorseedling nutrition at different stages of growth.

When many tests are planned, laboratory spacemay require two or more rooms. Soil screening andseed extraction procedures are “dirty” activities as-signed to one room; “clean” chemical tests and proce-dures are performed in another. Clean and dirty labs

are best located in separate buildings or differentareas of the same building. Sensitive equipment (pHmeters, spectrophotometers, atomic absorption units,etc.) requires continuous air conditioning to avoid cor-rosion of instrument parts in humid tropical climates.Other special needs for nursery labs are:. apparatus for making distilled water for chemical

tests;l fluorescent lighting;l voltage regulators to reduce power surges where

electrical power interruptions are common;. corrosion-resistant pipes in sinks where acid or al-

kaline chemical wastes are dumped;l scrubbers to clean’toxic elements from fumes vented

to outside areas;l corrosion-resistant exhaust fans to direct harmful

fumes away from seedlings, parking lots, andcommunal work or recreation areas; and

. cold storage to preserve chemical reagents, extrac-tions, and materials needed in soil and seed test-ing experiments.

4.7 Utility Lines

Good design and placement of irrigation and electri-cal lines keep production efficiency high by reducingmaintenance and repair costs. For example, locatingirrigation pipes and pumps near production areas re-duces both original and replacement piping costs (fig.2-4A). Shutoff valve locations should be shown onmaps of the nursery complex to help control emer-

19

gency situations when leaks occur. Placing supportsof overhead pipes away from roads and tractor alley-ways reduces accidental breakage of water lines.

Corrosion-resistant fittings are essential for waterlines and pumps, If irrigation water has high dis-solved salts; large aperture nozzle fittings are re-quired. A large supply of nozzles is needed where cor-rosion is a big problem.

Power and telephone lines are best placed under-ground to avoid potential damage from vehicles andstorms. If overhead lines are used, they should be keptaway from production areas and alleyways. Whenfeeder power and telephone lines are placed in produc-tion areas, trenches must be deep and well marked,particularly in bare-root beds where tractor-drawnmachinery is used. All water, power, and communica-tion line locations should be clearly marked on over-lays of the nursery complex blueprints.

4.8 Protection

4.8.1 Windbreaks. -Windbreaks are planted onwindward sides of production areas and germinationbeds to reduce drying, eroding, and abusive effects ofwinds on growing seedlings. Ameliorating effects ofwindbreaks extend several times the height of maturetrees (4). Large nurseries need several lines of wind-breaks to adequately protect seedbeds. Usually,species different from those produced ,in the nurseryare used because their seeds germinate like weedsand reduce effects of using improved seeds.

Species with large spreading root systems andcrowns are not suitable. Shade from them reducessunlight on nearby seedbeds; spreading root systemscompete with bare-root seedlings for water and nutri-ents. Any insect or disease outbreak in windbreaksshould be controlled quickly to reduce risk of spread tonearby nursery seedlings.

4.8.2 Shade and Nursery Bed Orientation.-Aneast/west orientation may be better than traditionalnorth/south bed orientation in the tropics if individ-ual, small covered beds are used rather than widespanshade houses. Justification for east/west orientationis based on: 1) need for some shade during the hottestpart of the day and 2) minimizing the amount of shad-ing material needed to provide shade protection forseedlings. Modern nursery management concepts alsoemphasize fostering as much environmental controlas practical to reduce dependence upon nature’swhims.

Puerto Rico lies at approximately 18” N. latitudefrom the equator. For maximum interception of thesun’s rays, the shade roof should be tilted about 18”towards the sun. In other words, the north side of theeast/west oriented shade roof should be higher thanthe south side (see Appendix 4 for a schematic view ofinclination direction).

2 0

LITERATURE CITED

1. Aldhous, J. R. Nursery practice. Forestry Commis-sion Bull. 43. London: Her Majesty’s StationeryOffice; 1972. 84 p.

2. Davidson, H.; Mecklenburg, R. Nursery manage-ment administration and culture. EnglewoodCliffs, NJ: Prentice-Hall; 1981. 450 p.

3. Escobar R., Rene; Espinosa B., Miguel; Medina V.,German; Quezada J., Leopoldo. Determinationde1 tamano de viveros forestales. Universidad deConception. Bol. Tee. 1. Los Angeles, Chile;1975. 16 p.

4. Kittredge, Joseph. Forest influences: the effects ofwood vegetation on climate, water, and soil, withapplications to the conservation of water and thecontrol of floods and erosion. New York: Dover;1973. 394 p.

5. Paul, Derek K. A handbook of nursery practice forPinus caribaea var. hondurensis and otherconifers in West Malaysia. United Nations De-velopment Programme, Food and AgricultureOrganization of the United Nations FO:SF/MAL12, Working Paper 19. Kuala Lumpur,Malaysia; 1972. 139 p.

6. Tinus, Richard W.; McDonald, Stephen E. How togrow tree seedlings in containers in green-houses. Gen. Tech. Rep. RM-60. Ft. Collins, CO:U.S. Department of Agriculture, Forest Service,Rocky Mountain Forest and Range ExperimentStation; 1979. 256 p.

7. Weber, Fred R. Reforestation in arid lands. PeaceCorps/VITA Publications Manual Series 37E.Washington, DC: Government Printing Office,1977. 240 p.

CHAPTER 5

5. PRODUCTION SCHEDULING

5.1 General Principles

The key to a successful nursery program is plan-ning and developing realistic timetables for all phasesof seedling production; this is called productionscheduling. Schedules are based on knowledge ofnursery physical plant limitations and managerialexperience. A detailed production and planningschedule like that described in Appendix 5 can bedeveloped for large, mechanized operations. Forsmaller nurseries, a simple flowchart shows essentialelements of seedling production (fig. 5-l).

needs/prioritiesSite - needs

Funds available Decide WhetherNursery is

Temporary orPermanent ?

ProductionScheduling

Select

Decide Method ofPropagation

Lobor Availabil i tyWater AvailabilitySupport Focilit iesRoads, Electricity,Communications

- ContainerVegetativePropagation

Bare RootI

Pest ‘1.Protect ion II,

LaterTending

C o r e

L i f t i n gb a n d

I T r a n s p o r t i n g 1

L/lOut-Planting

Procurement

I Out -PlantingI

Secure SuperiorClones/Hybridsor Phenotypes

vDecide Propagation

Technique:Cuttings, Layering,

or Graft ing

I+

TendingC a r e

‘1Transport

a n dOut-Plant

Figure 5-1 .--Floruchart of procedures fix successful nursery establishment and seedling production.

2 1

Before initiating production schedules, a managermust obtain all equipment, materials, and suppliesneeded to produce the desired number of seedlings (3,4,8 1. Managers work closely with all groups request-ing seedlings, including private industries, govern-ment agencies, and individuals. Maintaining goodworking relationships with nursery personnel is es-sential to smooth and efficient execution of productionschedules.

Each step in a production schedule is identified,then listed in sequential order. Major production stepsare then divided into minor ones. Breaking down theoperational process into individual steps allows amanager to prepare lists for needed equipment, mate-rials, and supplies. A good diagram will reveal poten-tial problems in the production process, or it mightindicate that more than one piece of equipment (e.g.,two soil mixers) are more efficient than one piece fora particular operation. Individual steps in the produc-tion process can be translated to a standard work unit,for example 1,000 seedlings per man/hour. All nurs-ery operations should be constantly under review forpotential improvement (1,2).

To make realistic production schedules, nurserymanagers must know how and where to use each pieceof equipment or procedure. They must be able to makeadjustments and repairs or know where and how soonrepairs can be made. Usually, they introduce newtechniques and ideas and train supervisors to usethem. Also, managers must 1) make sure laborers useequipment properly, efficiently, and safely and 2) stayabreast of new techniques and developments by read-ing nursery publications, visiting other nurseries,and attending nursery conventions on a regular basis.

Innovative nursery managers must not be contentto let local traditions and labor habits dictate seedlingproduction methods. If this happens, an entire pro-gram may be adversely affected. Periodic changes areoften required that might upset work habits and tra-ditions (7). To minimize conflicts with personnel andtraditions, managers must educate their employeesabout the reason for and benefits of any changes.

Managers should also be cognizant of special com-munity needs and realities. For example, although asemi-mechanized container operation may producemore seedlings in a shorter time than a less auto-mated, more labor intensive operation, the latter mayeventually be chosen. Such a decision would reflectlong-term reforestation as well as socioeconomic pro-gram needs to utilize unemployed local labor (5 1. Em-ploying local laborers promotes community self-helpand fosters grass roots acceptance of nursery and re-forestation objectives (9, IO ).

5.2 Some Specific Principles

5.2.1 Overall Planning and Coordination. -Coor-dination is required so that managers do not produceseedlings at the wrong time of the year. For example,

22

if normal planting lasts from the beginning of therainy season until 1 month before the rainy seasonends, seeds must be sown to produce seedlingsthroughout the entire planting season. If a forester incharge of planting needs 1 million seedlings of aspecific species, height, and age between August 1and December 1, the nursery manager must translatethis information to a production basis. A certain per-centage of each nursery crop contains cull seedlingsthat do not meet outplant specifications. Generally, atleast 10 percent more seedlings are produced than arerequested to allow for cull seedlings. The actual cullfactor is determined by careful observation over sev-eral years.

5.2.2 Disease.-Disease may also eliminate someseedlings, requiring an even greater margin of safety.The possibility of diseases killing a high percentage ofall seedlings is a constant threat in any nursery. Ifseedlings are produced on a staggered basis, thethreat of total crop loss from a single disease is mini-mized. Reducing losses from disease is crucial in areaswhere entomologists and pathologists are locally un-available.

5.2.3 Seedling Growth Rates. -Managers rely pri-marily on experience to determine how fast seedlingsgrow. For example, in some nurseries it may be possi-ble to produce P. caribaea seedlings 25-30 cm tall be-tween November 1 and May 1 (i.e., in only 5 to 6months). However, if seeds are sown in December, itmay take 6 to 7 months to produce the same-sizeseedlings. This time difference is caused by slowerseedling growth from February 1 to April 30, the nor-mal dry season in that nursery area. Productionscheduling is therefore based on expected growthrates determined by personal knowledge and previousgrowth records.

5.3 A Case Example

In this section a nursery production system is de-scribed in detail, with special emphasis on major oper-ational steps. Basic arithmetic calculations for deter-mining amounts of potting medium, seeds, and othermaterials needed are given in Appendix 9. The exam-ple is limited to production of P. caribaea seedlingsusing soil, plastic bags, and hand labor.

This concept can be applied to other species, and thesystem described can be established in almost anyarea having adequate water supply and level terrain.The system is easily modified to accommodate tempo-rary nurseries. In contrast, a highly mechanized con-tainer production system is discussed in Chapter 15.

For the plastic bag production system describedhere, assume that a nursery manager must produce1 million pine seedlings and that the seedlings areneeded between August 1 and December 1, the mostfavorable planting dates in his area. For adequatelead time to order new supplies, actual seedling re-quests should be submitted at least 1 year before the

projected planting date. Under usual growing condi-tions, P. caribaea seedlings are ready to outplant7 months after germination, when they are 25 to30 cm tall and have a root collar diameter of 5 mm. Ifseedlings are grown in large bags (~400 cc) with soil,they can usually be held in a nursery for 2 to 3 addi-tional months without seriously affecting their out-plant survival and growth. When held longer than7 months, potted seedlings must be root-pruned beforeoutplanting to remove balled or entwined roots. Rootpruning avoids potential problems of greaterwindthrow and disease incidence, which are associ-ated with poor root form.

An experienced nursery manager knows that aminimum of 7 months is required to produceplantable seedlings; this factor is taken into accountwhen making a production schedule. Ideally, the pro-duction process is split into several manageablephases, with subgoals of producing 200,000 healthyseedlings for outplanting on five dates the followingyear: August 1, September 1, October 1, November 1,and December 1. Staggered production avoids havingall seedlings ready to outplant on the same date.Furthermore, when seedling production is separatedinto distinct phases, there is less risk of seedling lossto a disease like damping-off.

The manager’s objective is to produce the qualityand quantity of seedlings ordered on dates specified.As stated in Sections 5.2.1 and 5.2.2, extra seedlingsare grown to replace cull seedlings and those killed bydisease. It is generally unwise to hold small or slow-growing seedings for long periods. Accumulated evi-dence shows that small, unhealthy seedlings are ge-

netically inferior to normal, vigorous seedlings andgrow more slowly after outplanting. To obtain vigor-ous seedlings, use quality seeds selected from superiortree seed sources whenever possible or ordered fromreputable seed suppliers.

A real problem with tree species in great demand ispurchasing adequate quantities of seeds. One exam-ple is P. caribaea var. hondurensis, for which 1 kilo-gram of seed in 1986 cost up to $300, with improvedseeds costing even more. Managers must make per-sonal contacts with seed dealers to arrange for sup-plies well in advance of anticipated.sowing and pro-duction runs. Once seeds arrive, managers mustdecide if and how they should be stored, when they areto be planted, and in what proportions (6). Sowingrates for a production run are estimated from repli-cated trials showing germination percentage for seedlots that will be sown. Remaining seeds are stored asdescribed in Chapter 6.

The most difficult part of any production run re-mains after sowing: growing seedlings to term. Con-stant monitoring is needed to determine moisture andnutrition needs. Vigilance is required to prevent in- .sects and diseases from destroying seedlings. Weedsmust be controlled. Additional concerns are abnormalshort-term climatic influences (droughts or abnor-mally rainy periods) that might affect seedlinggrowth and disasters like fires or hurricanes. Againstfires, the precautions mentioned in Chapter 12 shouldbe followed regarding facility security. If a hurricaneis imminent, containers should be moved to protectedareas (fig. 5-2). If bare-root beds are sloped properly

Figure 5-2.-Storage space under raised cement benches can be used to temporarilystore containerized seedlings during severe storms. Saran-covered boxframes on benches protect newly-sown seed in germination trays frombirds; using close-mesh metal screening instead of Saran will protecttrays against rats and mice.

23

and soils are well drained, bare-root stock will surviveall but the severest storms.

Once seedlings make it to term, they must still belifted, packed, and transported to the field. Improperprocedures in any of these later stages can causeundue mortality and reduce seedling vigor or health,As with all preceding production stages, only fore-sight and careful planning will avoid potential prob-lems such as lack of packing materials and pallets,transport vehicles, or proposed vacation schedules fordrivers and workers who must be present for thepacking and transporting phases.

Skilled managers review all production phasescarefully, well in advance of each production run. Ifplanning is executed rigorously and if nursery man-agers are observant of daily changes in natural andwork environments, each production run, large orsmall, should be successful.

LITERATURE CITED

1. Adlhous, J. R. Nursery practice. Forestry Com-mission Bull. 43. London: Her Majesty’s Sta-tionery Office; 1972. 84 p.

2. Davidson, H.; Mecklenburg, R. Nursery manage-ment administration and culture. EnglewoodCliffs, NJ: Prentice-Hall; 1981. 450 p.

3. Evans, J. Plantation forestry, in the tropics. Ox-ford: Clarendon Press; 1982. 472 p.

4. Lantz, Clark W., ed. and camp. Southern pinenursery handbook. Atlanta, GA: U.S. Depart-ment of Agriculture, Forest Service, SouthernRegion; 1984 (pagination varies).

5. Pardo, Richard D. Forestry for people: can itwork? Journal of Forestry. 83(12): 733-741;1985.

6. Paul, Derek K. A handbook of nursery practicefor Pinus caribaea var. hondurensis and otherconifers in West Malaysia. United Nations De-velopment Programme, Food and AgricultureOrganization of the United Nations FO:SF/MAL 12, Working Paper 19. Kuala Lumpur,Malaysia; 1972. 139 p.

7. Peace Corps. Forestry training manual. Wash-ington, DC: Inter America Region Office of Pro-gram Development, Forestry/Natural ResourceSector, Peace Corps; 1982. 390 p.

8. Tinus, Richard W.; McDonald, Stephen E. How togrow tree seedlings in containers in green-houses. Gen. Tech. Rep. RM-60. Ft. Collins, CO:U.S. Department of Agriculture, Forest Serv-ice, Rocky Mountain Forest and Range Experi-ment Station; 1979. 256 p.

9. Weber, Fred R. Reforestation in arid lands. PeaceCorps/Vita Publications Manual Series 37E.Washington, DC: Government Printing Office;1977. 248 p.

2 4

10. Weidelt, H. J., camp. Manual of reforestation anderosion control for the Philippines. Eachborn,Germany: Agency for Technical Cooperation,Ltd. (GTZ); 1975. 569 p.

CHAPTER 6

6. SEED PROCESSING AND STORAGE

Seeds bought on consignment are already extractedand cleaned but must be stored properly. However,when fresh seeds are collected from local sources, theymust by properly cleaned and prepared for eithershort- or long-term storage. This chapter reviews thefundamentals of seed processing and seed storage.More detailed information on these topics and on seedharvesting and transporting techniques is found inUSDA Forest Service Agricultural Handbook 450(17).

6.1 Fruit Types and Processing Practices

Seed processing includes drying and initial extrac-tion, cleaning, culling damaged or empty seeds, reduc-ing and maintaining proper moisture content, and, ifneeded, applying protective treatments like fungi-cides (2, 16). Processing techniques vary slightly forthe major fruit types: cones (pines), fleshy fruits(kadam and teak), and dry fruits (mahogany and Cor-dia sp.) The goal in processing each of these fruit typesis maximum production of clean, viable seeds.

Of these seed processing practices, the most impor-tant is obtaining proper moisture content. Excessmoisture can cause mold on seeds in storage. Mold isthe most serious threat to seed viability. Therefore,several seed drying techniques are discussed. Otherpractices also important when processing seeds in-clude cleaning, maintenance, and adjustment of ex-traction equipment; preventing accumulation offlammable dust, resin, or debris; following safetyguidelines; and using approved safety devices when-ever required (e.g., use of dust masks when separatingseeds from dirt and chaff).

6.2 Cones and Dry Fruits

6.2.1 Initial Inspection and Handling. -Newlycollected seeds must be carefully checked for disease,insects, mold, and external moisture or dampness(which could cause mold at a later stage). Using plas-tic bags for seed storage and transportation is unsatis-factory because impermeable plastic traps condense

maicture inrzide bags. Green cones, pods, and dryfruits usually contain lots of moisture (14). Conse-quently, heat buildup will occur inside the bagsthrough cellular respiration, and mold can then de-velop because of the humid, warm, and dark condi-tions in tightly packed bags. Thus, excess moisturemust be removed immediately after seeds arrive inthe nursery. Permeable paper, cloth bags, and cleanedburlap bags are best for collecting seeds; they arecheap and avoid moisture buildup, particularly whenseeds are packed loosely in them.

6.2.2 Air-Drying.-Most damp seeds, cones, orpods can be air-dried. They are placed on protecteddrying screens or trays that allow sunlight and air topass through but keep out rain. Cheap and effectivedriers use elevated racks, allowing air circulationfrom below (fig. 6-l). The same design principle isused for simple, portable seed drying racks or largedrying sheds.

Drying screens and racks are basic seed processingequipment. Because most seeds lose germinationvigor in processing, drying of external or surfacemoisture is done as quickly as possible. Seeds shouldnever be left for long periods in drying racks. Even atambient temperature, drying seeds will lose viability.Seeds are normally exposed to full sunlight for only 2or 3 days. For uniform drying, seeds are evenly spreadover the screens. A thin layer of seeds dries more

FINE MESII SCREEN

MOVABLE DRYING RACR

-_.LABEL RAINFALL

COLLECTOR’S NAMESTORAGE: BEGINNING DATEQUANTITY: NUMBER OF SEEDS 1R

CONTAINER

STORAGE 8 LABELING

Figure 6-l.-Seed drying and storage procedures. Adapted from121).

quickly than a thick layer. Seeds are stirred or turnedover 2 to 3 times each day, allowing exposure of theentire seedcoat to the sun’s rays. Air-drying is basi-cally a quick way to remove external seed moisture; itprepares seeds for sizing, dewinging, cleaning, andseparating filled from empty seeds (Appendix 6).

Processing large cone crops requires similar dryingprecautions. Sacked cones bundled too tightly cannotopen fully and will obtain a “set” that precludes seedextraction (3). Packing sacks too close together stopsadequate ventilation, causing heating and molding.

When small quantities of seeds are dried outside, onthe ground or on paved driveways, one must be able tocover them quickly or move them inside when it rains.Similarly, seeds must be covered during the eveninghours to avoid dewfall accumulation. A drying rackwith wheels is easily moved to sheltered areas(fig. 6-l). All seeds must be screened from rodents andbirds during drying.

6.2.3 Kiln-Drying. -Large quantities of seeds,cones, or pods are usually kiln-dried. Kilns havemany sizes and shapes. Two general types are therotating-drum kiln and the large conveyor-belt,progressive-type kiln. Drum kilns are fairly efficientbecause their rotating or tumbling action also sepa-rates seeds from pods or cones. For small seed batches,a small rotating-drum kiln is probably the best pur-chase. Seeds are removed from inside the drum assoon as possible because excessive tumbling is harm-ful.

Most large kilns are heated by natural gas or elec-tricity. The kind of fuel used has no influence on dry-ing; the least expensive or most readily available fuelis used. Large kilns have automatic controls thatgraduate and maintain specific heat and humiditylevels. If kilns have sensitive controls, cones areopened and seed moisture content is lowered suffi-ciently for long-term cold storage. When kiln-dryingcannot reduce seed moisture content sufficiently,seeds are dried further in convection ovens.

Kiln temperatures should not exceed 54°C for pines.Mahogany and cedar pods are forced open by kilndrying at 43°C. Kilns are readily constructed fromlocal materials. The major task is providing adequateair circulation and maintaining an even flow of uni-formly distributed heated air throughout the cham-ber. Drawings of custom made kilns are availableupon request (8).

6.2.4 Solar Dryers. -Solar dryers are used for ex-tracting seeds in the tropics, where the number ofdays with full sunlight is high. An experimental solardryer at ITF (fig. 6-2) is rountinely used to open ma-hogany pods, cedar pods, and pine cones and to dryseeds of various species. Under normal sunlight condi-tions, pods and cones open within 3 to 4 days. Failureto stagger cone collecting over normal field matura-tion results in an accumulation of large quantities ofcones that cannot be dried immediately because of a

2.5

Figure 6-2.-Solar dryers are effective for drying seeds as well aslumber. Many designs exist; they are easy to constructand require little maintenance. The one shown herehas fiberglass side and roof panels covering a treatedwood frame.

lack of space. If cones are improperly stored whileawaiting drying, they may mold.

Extraction may be done with a power-driven tum-bler inside a solar dryer. Because solar dryers operatemostly on radiant energy, the only cost involved, be-sides labor, is the small amount of electricity used bya small motor that turns the tumbler and runs anextractor fan that blows moist air from the dryer.Solar dryers are simple to build; a wide variety ofdesigns exists (13, 15). A clever carpenter can easilybuild a solar dryer, making special design adaptationsfor local conditions.

Because of design constraints, sensitivity control ofhumidity and temperature on solar dryers is not asprecise as that on manufactured kilns or ovens. More-over, heat buildup inside a solar dryer can fluctuatemore than what normally occurs in ovens or kilns.Thus, solar dryers are not routinely used for loweringseed moisture content.

Another problem that might occur is rupture of thesolar dryer. This is caused by expanding cones thatoccupy greater physical volume when expanded thanwhen closed. There have been cases where walls ofdrying buildings have been pushed out or roofs liftedoff as pine cones dried and expanded. Thus, one shouldalways leave sufficient room in large or small solardryers (about 50 percent of structure volume) for coneexpansion.

26

6.3 Fleshy Fruits

Seeds with fleshy coverings require different proc-essing than that required by cones and dry fruits (22).The kind of processing depends on whether seeds arecovered by thin or thick flesh. If fleshy fruits are notprocessed soon after they are collected, fermentationand spoilage occur because high moisture and sugarcontent of the flesh favor bacterial and yeast growth.

Flesh is removed by hand or machine methods.Kind, quality, and value of the fruit determine whichmethod is used. Small seed lots are usually maceratedby hand: by squeezing, mashing, or rubbing fruitsagainst wooden blocks or screens. Using nested sievesheld under running water allows pulp to be washedaway while retaining seeds.

Heavier seeds of fleshy fruits are separated by flota-tion. Macerated debris and seeds are placed in aslightly tilted bucket. A strong stream of runningwater from a garden hose is then directed against thecontainer side, creating a swirling and lifting effect.Empty seeds, pulp, and other debris float to the sur-face and exit in overflow water. Good seeds are heav-ier; they sink and are trapped in the container.

Large seed lots are best processed using feedgrinders, concrete mixers, or commercial maceratorsand separators (fig. 6-3). Some machines free onlyflesh from the seed, leaving seeds and residues thatare separated in a later cleaning. Other equipmentseparates pulp from seeds and cleans seeds in a singleoperation. A flotation procedure is used to separateseeds from pulp and debris, as explained above. Thin-fleshed seeds like teak require no macerating, onlydrying after initial cleaning and washing.

After fruits are macerated and seeds are separatedand washed, seed surfaces must be dried. This can bedone indoors or outdoors on any clean surface that issheltered. In moist climates where air-drying is notsufficient, kilns or ovens are used. Final cleaning andseparating is done using air-screens or air-columns(fig. 6-4) to remove chaff and light debris (18,191.

6.4 Moisture Content Considerations

Kind of seeds, maturity, presence of fungi or bacte-ria, and prestorage treatment all influence longevityand viability of stored seeds. In general, optimum con-ditions for maintaining high seed viability over longperiods are a combination of low seed moisture con-tent and low ambient temperature during storage (10,11,12).

High seed moisture content causes several prob-lems. At 30-percent moisture content or above, seedsmay germinate if the storage temperature is too high.If moisture content of stored seeds is between 15 and30 percent, germination is improbable, but cellularrespiration of stored nutrients in the endosperm low-ers seed viability. Reducing seed moisture content tobetween 10 and 12 percent effectively eliminates most

Figure 6-3.--Separating large seeds from fleshy fruits.

of these problems. However, fungi can still survive inthis moisture content range, and molds can develop.Insects will even attack seeds when moisture contentsare as low as 8 to 9 percent if they are stored abovefreezing temperatures.

In areas without refrigerated storage, seeds areoften stored at ambient temperatures of 20” to 35°C.When seeds stored at higher temperatures are chemi-cally treated to avoid insect and disease attack, inter-nal moisture content will equilibrate at 8 percent ifstorage room relative humidity is maintained at 40percent and room temperature is <13”C. If relativehumidity is 60 percent and storage room temperatureis 7”C, seed moisture content will eventually equili-brate to 12 percent. Wakeley (20) developed a chartfor determining equilibrium of seed moisture contentof longleaf pine in relation to temperature and rela-tive humidity of a seed storage area (fig. 6-5).

The most accurate way to determine seed moistureis the oven-drying method of the International SeedTesting Association (7). Oven-drying measurement ofmoisture content is explained in Chapter 7. If mois-ture content is too high (2 12 percent), seeds should bedried at 55”C, following instructions and precautionsoutlined in Chapter 7. Electronic moisture detectorsdetermine seed moisture content with sufficient accu-racy to permit their use in seed laboratories.

6.5 Cleaning and Storage

Because cold storage is costly and uses space, sepa-rating empty from full seeds before storage is essen-

tial in seed processing. Several methods exist thatseparate seeds by endosperm content. Mechanicalseparation, involving a vibrating table held at a slant,is the most common method. Another method uses anair stream in baffled tubes (fig. 6-4). Percentage of fulland empty seeds is estimated by sampling techniquesusing a low number of seeds. Flotation can be used toseparate empty seeds U2), but moistened full seedsmust be dried to stop mold development. In one in-stance, fire was used to separate balsa seeds fromsurrounding down-like material (5 ).

If seeds are sown shortly after collection, they canbe stored temporarily at normal refrigerator tempera-tures of 2” to 3°C. Seeds of P. caribaea store fairly wellin refrigerators if moisture content is less than 12percent. Refrigerated seeds lose approximately 1.5 to2.5 percent germination capacity per month. If stor-age is longer than 4 months, moisture content shouldbe lowered to < 10 percent and the seeds should befrozen. Seeds of kadam and Eucalyptus deglupta storeslightly better, with a germination loss of less than1 percent per month. Because mahogany seeds loseviability quickly, even if refrigerated, they should besown within 1 month of collection.

Seeds refrigerator-stored in sealed containersshould not be removed unnecessarily. Condensationof moisture on inside container walls helps mold de-velopment. If seed subsamples must be removed fromtime to time, seeds should be stored in smaller pack-ages, allowing minimal exposure to moisture.

Routine long-term storage of 5 to 10 years for manytree and shrub species, especially pines, is obtained by

27

Figure 6-4.-Mechanical separation of full and empty seeds bybaffle-tube, air-column technique.

R E L A T I V E H U M I D I T Y ( P E R C E N T )

Figure g-B.--Chart for determining equilibrium of seed moisturecontent of longleafpine when temperature and relativehumidity of seed storage area are known. Taken from1201.

28

freezing at 0°C or lower temperatures, with seed mois-ture content between 5 and 10 percent. Long-termstorage is important for storing genetically superior,scarce pine provenance seeds and for storing bumperseed crops. Dry tree seeds have tolerated extremelycold temperatures of -200°C (4 1; however, such lowtemperatures are not practical for long-term storage.More specialized methods, including storage underpartial vacuum (I 1, storage in an inert gas such asnitrogen (9), and replacing oxygen with carbon diox-ide in storage containers (61, have had various de-grees of success with certain species. Such methodsare not practical for most seed storage operations, par-ticularly in most developing countries.

Choice of containers for seed storage depends onwhether storage is short or long-term. For the latter,rigid-walled containers (e.g., glass) that restrict airand moisture entry are preferred. These, designatedas “tightly closed,” are seldom completely airtight orsealed, i.e., completely impermeable to entry of airand moisture (fig. 6-l).

When needed, internal moisture content can be con-trolled by using silica gel, charcoal, or chemical solu-tions, as long as these have no adverse effect on theseeds. For short-term storage, plastic bags are cheap,effective alternatives. If tied properly, they excludemoisture but allow exchanges of oxygen and carbondioxide with outside air. Remember, however, thatplastic bags are not used for seed collection (Sec.6.2.1).

LITERATURE CITED

1. Barton, Lela V. Seed preservation and longevity.New York: Interscience; 1961. 216 p.

2. Von Deichman, Vollrat. Nocoes sobre sementes eviveiros florestais. Univ. Federal do Parana.Curitiba, Brazil; 1967. 196 p.

3. Dorman, Keith W. The genetics and breeding ofsouthern pines. Agric. Handb. 471. Washing-ton, DC: U.S. Department of Agriculture; 1976.407 p.

4. Engstrom. Albert, Will super deep freeze damagetree seed? Tree Planters’ Notes. 77: 28-29;1966.

5. Holdridge, .L. R.-A rapid method of extractingbalsa seed. Caribbean Forester. l(2): 25; 1940.

6. Holmes, G. D.; Buszewicz, G. The storage of tem-perate forest tree species. Forestry Abstracts.19: 313-322,455-476; 1958.

7. International SeedTesting Association. Interna-tional rules for seed testing. In: Proceedings,International Seed Testing Association. 31: l-1 5 2 ; 1 9 6 6 .

8. McConnel, James J. A portable kiln for dryingsmall lots of pine cones. In: Proceedings, Inter-national symposium on seed processing.

IUFRO Working Party S2.01.06. Bergen, Nor-,way; 1973. Pap. No. 11, Vol I. 14 p.

9. Magini, E. Forest seed handling, equipment andprocedure. II. Seed treatments, storage, testingand transport. Unasylva. 16: 20-35; 1962.

10. Marrero, Jose. A seed storage study of maga.Caribbean Forester. 3(4): 173-184; 1942.

11. Marrero, Jose. A seed storage study of some trop-ical hardwoods. Caribbean Forester. 4(3): 99-106; 1943.

12. Marrero, Jose. Tree seed data from Puerto Rico.Caribbean Forester. 10: 11-36; 1949.


14. Bin Mohamad, Aminuddin; bin Ibrahim, Zakaria.Grading of Gmelina arborea (Yemane) fruits bycolour. The Malaysia Forester. 43(3): 337-339;1980.

15. Perdue, Robert E., Jr. Field drying plant materialcollected for chemical and biological screening.I. Portable facility for sun drying. EconomicBotany. 36(4): 369-372; 1982.

16. Tanaka, Y. Assuring seed quality for seedlingproduction: cone collection and seed processing,testing, storage, and stratification. In: Duryea,Mary L.; Landis, Thomas D., eds. Forest Nurs-ery Manual: production of bareroot seedlings.The Hague, the Netherlands: Martinus Nijhoff/Dr W. Junk Pub.; 1984: 27-39.

17. United States Department of Agriculture, ForestService. Seeds of woody plants in the UnitedStates. Agric. Handb. 450. Washington, DC:U.S. Department of Agriculture, Forest Ser-vice; 1974. 883 p.

18. Venator, C. R.; Zambrana, J. A. Extraction andgermination of kadam seed. Res. Note ITF-14.Rio Piedras, PR: U.S. Department of Agricul-ture, Forest Service, Institute of TropicalForestry; 1972. 2 p.

19. Venator, C. R.; Zambrana, J. A. Extraction andgermination of kadam seed. Res. Note ITF-14A.Rio Piedras, PR: U.S. Department of Agricul-ture, Forest Service, Institute of TropicalForestry; 1975. 3 p.

20. Wakeley, Philip C. Planting the southern pines.Agric. Monog. 18. Washington, DC: U.S. De-partment of Agriculture, Forest Service; 1954.233 p.

21. Weber, Fred R. Reforestation in arid lands. PeaceCorps/VITA Publications Manual Series 37E.Washington, DC: Government Printing Office;1977. 248 p.

22. Woessner, R. S.; McNabb, K. L. Large scale pro-duction of Gmelina arborea Roxb. seed-a casestudy. Commonwealth Forestry Review. 58(2):117-121; 1979.

CHAPTER 7

7. SEED TESTING

Several tests assess the physical d;nd biological as-pects of seeds (14). Test results help determine priceif seeds are sold, indicate the number of seeds to sowper unit area of nursery for a production run, andevaluate available seed stocks for reforestation pro-grams. Many tests are now standardized internation-ally, allowing better communication among nurserymanagers, foresters, and scientists working withseeds.

Seed tests are commonly done immediately follow-ing extraction and shortly before actual sowing. Sometests are done periodically on seed lots kept in long-term storage. Only brief summaries of the more com-mon tests are given; detailed descriptions of tests andseed testing problems appear elsewhere (8,10, 15).

7.1 Sampling

A single seed lot can be large or small; it may fill anentire cold storage room or one small bag. To guaran-tee reliability of seed test results for large lots, alltests must be run on representative samples of theentire lot. Seed triers (fig. 7-l) draw seed samplesfrom large bags or boxes. Electrical sample dividersthen split the sample into two or more subsamples onwhich purity or germination tests are run. For smallnurseries, common sense, clean hands, a clean work-bench, and a large-bladed knife are sufficient for mostseed testing tasks.

Required sample sizes vary according to numberand kind of tests run. For germination, at least 600seeds are needed; a complete seed analysis requires atleast 2,500 seeds. Minimum working sample sizes fortree seeds are given in table 7-l. If low viability or alarge amount of empty seeds are suspected, then min-imum sample sizes (weights) should be double or per-haps triple those listed in table 7-1.

If seeds are stored in large boxes or crates, handsamples are taken at the top, center, bottom, and sidesof the box. Samples are taken in proportion to size ofthe box or container. One should take twice theamount of seeds from a 0.5-m3 box than from a 0.25-m3 box. When seeds are stored in small bags, mixthem thoroughly before sampling. For small lots of 1to 6 bags, sample each; for more than 6 bags, the ruleof thumb is to sample 10 percent of the total numberof bags plus 5 (f5), as shown below.

29

Number of bags Number of bagsin seed lot to be sampled

8 610 620 735 950 10

100 15

For a lot size of 8 bags, 10 percent of 8 is 0.8 or 1when rounded off; then 1 + 5 = 6 bags to be sampled.

7.2 Weight

Accurate seed weight is necessary to calculate nurs-ery sowing rates. Weight is normally expressed for1,000 full seeds. Factors affecting seed weight aresize, moisture content, and proportion of full seeds inthe lot. One can count out and weigh 1,000 seeds, or,as is done more routinely, 10 random samples of 100seeds each are taken from a pure batch and weighed(8). For commercial testing, weights are recorded tothree significant digits; for small nurseries, one sig-nificant digit is enough. Besides the mean seed weightin grams, other useful data include the standard devi-ation, standard error, and coefficient of variation ofthe seed samples (Chap. 14).

To convert the weight of 1,000 seeds in grams tonumber of seeds per pound:

453,600weight of 1,000 seeds in grams = number of seeds per

pound;

similarly,number of = reported 1,000 seed weight in gramsseeds per 1,000gram

7.3 Purity Analysis

Purity tests determine the percentage of true seedsand other material in a seed lot. The four recognizedcomponents are pure seed, other seeds, weed seeds,and inert matter such as seed wings, broken cone

Figure ‘I-l.-Seed triers for obtaining representative seed samplesfor germination’ tests. With slots open, triers are in-serted into seed lots; when slots are closed, seeds aretrapped and can be used for seed testing after trier isremoved.

Table ‘I-l.-Minimuti sample sizes for seed testing’

Seedsper

kilogram

Minimumworkingsample

size

Seedsper

gram

Number Gmms Number

less than 4,4002 5003 less than 524,400~5,500 300-400 5-75,500-6,600 200-300 7-106,600-7,700 140-240 10-157,700-8,800 100-170 15-208,800-9,900 85-125 20-259,900-11,000 70-100 25-30

ll,OOO-12,000 60-90 30-3512,000-13,000 54-75 35-4013,000-15,000 42-65 40-5015,000-18,000 36-54 50-6018,000-20,000 30-46 60-7020,000-22,000 27-40 70-8022,000-23,000 24-35 80-9033,000-44,000 22-32 go-10044,000~55,000 17-28 loo-12555,000-66,000 15-23 125-15066,000-88,000 13-20 150-17588,000-110,000 11-17 175-200

110,000-143,000 9-15 200-250143,000-176,000 8-12 250-300176,000-220,000 6.5-10 300-350220,000-331,000 5.5-8.5 350-400331,000-441,000 4.4-7.5 400-500441,000-661,000 3-6 500-750

more than 661,000 3 more than 750

‘Source: Association of Official Seed Analysts 1970.2Purity analyses are rarely required for seed samples of this size.3Sample should contain at least 500 seeds.

scales, rocks, twigs, or other non-seed material. Com-mercial germination tests use the pure seed compo-nent only. Each component is usually expressed aspercentage by weight of the original sample. Thus, ifthe initial weight of a P. caribaea seed sample was60.124 g and the pure portion weighed 52.467 g, pu-rity of the lot is:

52.467- x 100 = 87.3 percent.60.124

Purity tests are meticulous, slow operations. Sepa-ration is done best by working on a board or raisedplatform about 8 to 15 cm above normal table height.A multiple-tube daylight fluorescent light is best.Other required equipment are forceps and spatula forseed handling and separating, a wide-field hand lensof 5 to 7~ power, a wide-field stereomicroscope withmagnification from 10 to 75 x , seed pans, and a bal-ance. Analytical balances that weigh to three or foursignificant digits are used in international seed test-ing labs. Tortion-bar and other balances that weigh toonly one significant digit are suitable for small nurs-eries.

30

!&po&& is dono manually by placing about 400seeds on the working board or bench, drawing a fewseeds at a time from the main pile, spreading themapart, and finally determining into which componenttray or pan the material should be placed. After pre-liminary separation is made, all components arerechecked.

Imperfect seeds of the same species being checkedare not classified as other seeds or inert matter. How-ever, immature, shriveled, cracked, and damagedseeds larger than one-half the original seed size, in-cluding those with internal insect damage and thosestarting to germinate, are designated as “pure” seed.This may seem strange, but germination potential isdetermined by a germination test, not a purity test.

7.4 Moisture Content

Seed moisture content has an inverse relationshipwith seed longevity and germination capacity: at highseed moisture (2 18 percent), seed germination capac-ity and longevity are lower. Managers check seedmoisture content soon after receiving fresh seeds orseeds that have been in transit a week or more. Also,periodic checking every 6 months is essential for mon-itoring viability of seed lots kept in long-term storage(12 ).

The common laboratory test for determining seedmoisture content is the air-oven method developed bythe International Seed Testing Association (8). It isprescribed for all tree and shrub seeds except thosefrom fir (Abies), cedar (Cedrus), beech (Fugus 1,spruce Vicea ), and hemlock (Tsuga ). Seed from thesegenera contain oils and resins that are volatile at105°C.

In the air-oven technique, a representative seedsample is weighed to three decimal places, dried at103” + 2°C for 17 ? 1 hour, and reweighed after cool-ing in a desiccator for 30 to 45 minutes. Percent mois-ture (i.e., seed moisture content) is obtained by divid-ing the weight of water lost in drying by the wetweight or weight before drying. Duplicate determina-tions are run on the same seed lot being tested. Ifresults differ by >0.2 percent, another duplicate de-termination is made, following the same procedures.

For example, assume that wet weights of duplicatesamples A and B are 20.197 and 20.186 g. After 17hours, dry weights for A and B are 18.062 and 18.002g respectively. Seed moisture contents are:

A. = 20.197 - 18.06220.197 x 100 = 10.6 percent, and

B. = 20.186 - 18.00220.186 x 100 = 10.8 percent.

Since the difference in moisture contents between Aand B was 0.2 percent, no retest is needed.

If seed moisture contents are known to exceed 17percent, seed subsamples are weighed, predried at55°C for 5 to 10 minutes, reweighed after cooling, andthen run through the normal air-oven technique. Per-centage of moisture is determined by dividing theweight of water lost from the two drying periods byinitial wet weight.

For example, assume that initial wet weight of aseed sample is 26.000 g and that an electronic seedmoisture meter showed a seed moisture content of 32percent. To check this, the seed sample is dried at55°C for 10 minutes. The resulting weight (W) of20.197 is an initial loss of 5.803 g (Wi). After dryingfor 17 hours at 103”C, the second weight is 18.062 g,an additional loss of 2.135 g (Wzl.

Actual seed moisture content for the sample is:

Weight loss Wl + W2 x 1oo orinital wet weight ,

5.803 + 2.13526.000 x 100 = 30.5 percent.

When reporting results, one must always specifiywhether percentage of moisture was obtained by di-viding by wet or dry weight. In the United States, seedmoisture content is usually expressed as a percentageof oven dry weight after the 17-hour drying. This pro-cedure differs from international custom where ex-pression on a wet weight basis is almost always used.Conversion from a wet to dry weight basis is doneeasily by using the scale shown in figure 7-2.

In commercial seed testing, the toluene distillationmethod replaces the air-oven method for determiningseed moisture content of species having resins orother materials that volatilize at 105°C. The methodinvolves grinding seeds finely, boiling them in atoluene apparatus, collecting condensed moisture in aseparate tube, and determining moisture content ofthe seeds by using their initial weight and weight (orvolumes) of water collected in the distillation appara-tus. Most nurseries do not have access to such special-ized equipment. Therefore, oven drying at 103°C for17 + 1 hour is satisfactory for determining seed mois-ture content of most species.

Figure 7-2.-Conversion from wet to dry weight basis when deter-mining seed moisture content. Taken from 11,5).

31

7.5 Germination Potential

Germination potential is determined from the pureseed component of purity tests. Alcohol is sometimesused to separate viable from nonviable seeds (6).When pure sebds are not available, representativesamples of lots should be tested as long as estimatedpurity is 298 percent (I). Results from germinationtests help determine value of the seed lot, whether itshould be used in the current planting season, if it canbe stored for future years, and what sowing ratesmust be used in nursery beds to meet establishedseedling production goals (16 ).

The science of germination testing is complex, cov-ering such areas as equipment (cabinets, rooms, ortrays and dishes), suitable medium (paper towels,sand, peat moss, etc.), procedures (moisture, light, andtemperature regimens), and (evaluation classifyingnormal and abnormal seedlings). Once germinationtest results are judged satisfactory for a particularspecies, techniques and methodology should be stand-ardized and continued in all future germination tests.When tests are standardized and routine, direct corre-lations between seed testing results and seedling fieldperformance can be made by nursery and field man-agers for specific locations and circumstances.

7.5.1 Germination Test Procedures. -In any ger-mination test, seeds must be thoroughly mixed andrepresent, tive

fsamples drawn randomly by hand or

with seed triers (fig. 7-l). Replicated tests are runusing at least 600 seeds in 6 replicates. If 100 seeds donot fit in test trays, smaller replicates of 50 or 25 seedsare used. The mean germination rate (expressed inpercent) for all replicates is used to calculate the num-ber of seeds needed fqr actual sowing (Appendix 9).Some seeds require pretreating such as cold stratifica-tion or fseedcoat scarification before germination(Chap. 8) or require certain temperatures for best ger-mination (3 ).

Some germination tests are still done outdoors inflats containing sand, peat, vermiculite, or soil. Al-though such test conditions are good for large-seededspecies such as teak, control of moisture and tempera-ture cannot be maintained for outdoor tests. Outdoortests have added risks of damage or loss of seeds bybirds, rodents, or insects.

Indoor germination tests are conveniently run insmall ;or large petri dishes or other trays; homemadecabinet germinators are also used (4 ). These should besterilized before a test is started. Common substrataare moistened filter paper, paper towelling, blotters,or commercial paper tissues such as Kimpak. Papersubstrata are nontoxic to germinating seedlings, freeof molds and other harmful micro-organisms, and pro-vide adequate moisture and aeration. Paper substratacan favor fungi if too much water is added, i.e., whenwater is seen collecting around seeds in the tray or if

32

a film of water forms on fingers after squeezing thepaper. Fungi are controlled by spacing seeds widelyand by removing seeds after they are fully germi-nated. If substrata such as washed sand or perlite areused for large seeds, seeds are covered loosely with thematerial, usually to a de&h equal to one-half theirdiameter.

In the tropics, the indoor and outdoor temperaturesrange between 20°C and 30°C which are suitable forgerminating most forest seeds (2 ). Germination testsshould not be done in poorly ventilated buildingswhere temperatures exceed 30°C or in air-conditionedoffices cooled to ~20°C. One exception is teak seeds,which require alternating kemperatures of 35°C to38°C for successful germination (11). Covering germi-nating trays maintains adequate humidity and mois-ture. Seeds exposed to very high humidity and tem-perature before testing will have low germination,invalidating test comparisons (7). Another exceptionis Pinus uyacahuite. Recommended germination for itis 25°C for 44 days or for 28 days after removing 3 to4 mm of the seedcoat from the radicle end of seeds.

7.5.2 Seedling Euabation. -Germination is theemergence and development from the seed embryo ofall essential structures, showing a seed’s capacity toproduce a normal, healthy plant under favorablegrowing conditions. Abnormally germinatedseedlings do not count as “being germinated.” Theymay, however, be counted and placed in abnormalgermination classes such as weak, rootless, or brokenseedlings; albino or translucent seedlings; andstunted or malformed radicles. Seedlings with fungalor bacterial damage can be counted as “germinated” ifthey are otherwise normal.

Test durations vary according to species and seedsize within species (5). At one extreme, teak seeds cantake up to 1 year or longer; for other species, 3 to 4weeks are usually sufficient. Counts should be madeevery 2 or 3 days, or more often for rapidly,germinat-ing seedlings.

Remaining ungerminated seeds are added to thetotal number germinated to give the percentage of fullseed in the sample. If cutting tests reveal many fullbut ungerminated seeds, pretreatment technique orgermination environment should be changed. Retest-ing is necessary when: 1) a large percentage of seedsremain ungerminated and 2) a variation among testreplicates exceeds that judged acceptable by past ex-perience or tolerances commonly allowed (table 7-2).Cumulative germination curves can be prepared andkept to identify higher quality seed lots (fig. 7-3).

“Quick tests” for determining seed viability are alsopossible. The most common, but least reliable, is thecutting test. Seeds are cut or split with a knife, andonly those having healthy, firm, and undamaged en-dosperms are judged viable (15). Biochemical stain-

Table 7.2.-Germination tolerance among 4 or more replications of100 seeds each’

Tolerance

Mean germinationvariation

amongreplications

---------------------------percent __________________________

96 or over 590 or over but less than 96 680 or over but less than 90 770 or over but less than 8 0 860 or over but less than 70 9Less than 6 0 10

Qource: (1).

0 4 6 12 I6 20 24 28

TEST PERIOD (DAYS,

Figure ‘I-3.-Typical cumulative germination curves for two seedlots of one tree species.

ing, using tetrazolium (TZ) salts, or embryo excisiontests require experienced technicians for performinganalysis and interpretations. Soft X-ray tests are evenfaster than staining tests and indicate insect or proc-essing damage as well. Initial expense for X-ray unitsand additional expenses in purchasing and develop-ing film probably limit this technique for most tropi-cal nurseries. The X-ray technique has been used suc-cessfully for teak (9).

7.6 Other Special Tests

Several other seed tests may have implications forparticular nursery operations.

7.6.1 Seed Vigor.-Vigor is a rather loose termused to describe observable germination differencesin seed lots of similar or different genetic makeup. Forexample, seed lots A and B in figure 7-3 both showedcumulative 70-percent germination in 30 days. Lot A,however, achieved this percentage in only 14 days,even though both lots were of the same species andwere exposed to the same overall germination condi-

tions. Other examples of vigor besides rapid germina-tion are germination under adverse conditions, resis-tance to fungal or other diseases, and correspondingvigor carry-over to nursery and planted seedlings.

The most common expression of vigor for tree seedsincludes assessing speed of germination, also knownas germinative energy. This is defined as the percent-age of germination at the peak rate of germination.Slow germinating lots (Lot B, fig. 7-31, are difficult todetermine. A more common expression is total num-ber of days required for a certain proportion of totalgermination to occur (e.g., 85 percent of P. caribaeavar. hondurensis seeds in 14 days). Such definitionsare possible from long-term observations or experi-ence of nursery managers, but they are seldom pub-lished or quantified through repeated and replicatedtrials.

7.6.2 Indirect Indices of Seed Vigor. -Indirect in-dices of seed vigor include biochemical staining testsusing tetrazolium. Several vigor classes can be devel-oped, based on partial or complete staining of the em-bryo and location of dead or damaged tissue. A majorproblem is standardization of test results. A success-ful technique exists for eucalyptus (13). Other bio-chemical tests exist, but most require sophisticatedtechniques and controlled laboratory environment,which are seldom available to field nurseries.

LITERATURE CITED

1. Association of Official Seed Analysts. Rules fortesting seeds. Journal of Seed Technology. 6(2):1-126; 1981.

2. Belcher, Earl. Optimum germination tempera-tures for seeds of six Central American pinespecies. In: South, David B., ed. Proceedings,international symposium on nursery manage-ment practices for the southern pines; 1985 Au-gust 4-9; Montgomery, AL. Auburn, AL:School of Forestry, Alabama Agricultural Ex-periment Station, Auburn University; 1985:89-93.

3. Gupta, B. N.; Kumar, Adarsh. Interrelated effectsof temperature and moisture on seed germina-tion of Dendrocalamus strictus Neis. The In-dian Forester. 103(3): 212-219; 1977.

4. Gupta, B. N.; Kumar, Adarsh. A low cost cabinettype seed germinator. The Indian Forester.103(5): 356-358; 1977.

5. Bin Haji Ahmad, Darus. Effect of fruit size upongermination of teak (Tectona grandis). TheMalaysian Forester. 43(3): 396-397; 1980.

6. Howcroft, N. H. S. A direct sowing technique forPinus. Tropical Forestry Research Notes S.R. 4.Bulolo, Papua, New Guinea: DepartmentForests; 1973. 9 p.

33

7. Bin Husin, Razali; Ong, T, H, Germination of lo-cally produced pine seeds in PeninsularMalaysia. The Malaysian Forester. 43(l): 124-125; 1980.

8. International Seed Testing Association. Interna-tional rules for seed testing. Seed Science andTechnology. 4: 4-177; 1976.

9. Kamra, K. The x-ray radiography of teak seed(Tectona grandis L. 1. Paper 9. In: Proceedings,international symposium on seed processing.IUFRO Working Party S2.01.06. Bergen, Nor-way; 1973. 14 p. Vol. I.

10. Kozlowski, T. T., ed. Seed biology. New York:Academic Press; 1972. 447 p. Vol. II.

11. Krishna Murthy, A. V. R. G. Problems of teakseed - 2. Germination studies. Paper 21. In: Pro-ceedings, international symposium on seedprocessing. IUFRO Working Party S2.01.06.Bergen, Norway; 1973. 24 p. Vol. II.

12. Marrero, Jose. Tree seed data from Puerto Rico.Caribbean Forester. 10: 11-36; 1949.

13. Perera, W. R. H. Seed for Sri Lanka’s reforesta-tion programme. Paper 23. In: Proceedings, in-ternational symposium on seed processing.IUFRO Working Party S2.01.06. Bergen, Nor-way; 1973. 14 p. Vol. II.

14. Tanaka, Y. Assuring seed quality for seedlingproduction: cone collection and seed processing,testing, storage, and stratification. In: Duryea,Mary S.; Landis, Thomas D., eds. Forest Nurs-ery Manual: production of bareroot seedlings.The Hague, The Netherlands: MartinusNijhoff/Dr W. Junk Pub.; Corvallis, OR: ForestResearch Laboratory, Oregon State University;1984: 27-39.

15. United States Department of Agriculture, ForestService. Seeds of woody plants in the UnitedStates. Agric. Handb. 450. Washington, DC:U.S. Department of Agriculture, Forest Serv-ice; 1974. 883 p.

16. Venator, C. R.; Macia Sanabria, F. A problem ofempty seed in Pinus caribaea in Puerto Rico.Turrialba. 23(4): 473-474; 1973.

CHAPTER 8

8. SEED PRESOWING TREATMENTS

Presowing seed treatments (pretreatments) areneeded to break seed dormancy resulting from eithera hard seedcoat or an immature embryo. A classicexample is teak seeds, with a hard seedcoat, whichmay not germinate for 2 or 3 years after sowing (4).

Dormancy is beneficial for natural regeneration of aspecies because it postpones germination until favor-able growing conditions exist. But irregular or de-layed germination is disastrous for nurseries, whereall seedlings must reach uniform outplanting size byspecific dates. The purpose of pretreating is to breakseed dormancy and to obtain uniform germination.

The ability of pretreatment methods to overcomedormancy varies greatly by species. In general, seedsof species growing in warm and moist tropical areasdo not need pretreatment (e.g., P. caribuea ). However,species from cool temperate and dry tropical areaswith distinct seasons may need some sort of pretreat-ment before uniform germination can occur (e.g.,Pinus tropic&is and Albizzia falcata 1. Some pretreat-ment methods commonly used in nursery work forspecies planted in the tropics and subtropics are sum-marized in Appendix 8. Sometimes, treatment withchemicals does not break dormancy but enhances ger-mination (3, 8).

8.1 Breaking Seedcoat Dormancy

Seedcoat dormancy is corrected by breaking thehard and impermeable coat surrounding seeds (e.g.,legumes and teak) by chemical or mechanical meth-ods.

8.1.2 Acid Scarification. -A common chemicalmethod is scarification with commercial grade sulfu-ric (H$SO,) acid (6). Several safety precautions mustbe followed when using the acid-soak method. Theseinclude using acid resistant wire containers or screensfor handling, draining, and washing seeds; providinga good source of running water; establishing a safearea to drain and dilute the acid obtained from rins-ing; and finding an area to dry seeds after rinsing.

Complete methodology and precautions are givenin Agricultural Handbook 450 (7). Determine the op-timum immersion time for individual species needingpretreatment. Some species require 15 to 60 minutesof soaking, others require up to 6 hours. Immersiontime is determined by soaking several small seed lotsfor different times in acid, followed by soaking inwater at room temperature for 1 to 5 days. The acid-soak treatment that yields the highest percentage ofswollen seeds (caused by water uptake), without split-ting seeds or exposing their endosperm, is the besttreatment. If differences in seedcoat composition existbetween lots, separate treatment times may be re-quired. Lots up to 100 kg are treated effectively byplacing a wire screen filled with seeds inside a metaldrum (fig. 8-l). Another alternative for thin-coatedseeds is to place them in a conical pile on a flat, hardsurface, apply acid at a rate of 2.5 kg per 36 kg ofseeds, mix thoroughly with a shovel, rinse, and drythe treated seeds.

34

Figure 8-l.-Acid pretreatment of large seed lots using wirescreens and metal drums.

Advantages of acid scarification are: 1) little or nospecial equipment, 2) low cost, and 3) recovery of acidfor future pretreatment (unless the pile method isused). Disadvantages are: 1) length of treatment mustbe carefully determined, 2) temperature must be con-trolled, particularly when large lots are pretreated,and 3) acids are hazardous substances.

When acid is used, NEVER ADD OR SPLASHWATER ON ACID because a violent reaction or ex-plosion can occur!

X.1.2 Water Soaking.-Alternate soaking in hotand cold water is the other major chemical method forpretreating seeds. For large seeded species like teakand legumes, success is achieved best with hot water.This method involves preheating water, 4 to 5 timesthe seed volume, to temperatures of 77°C to lOo”C,submerging the seeds, and allowing them to soak inthe gradually cooling water for 12 to 24 hours. Somespecies have seeds that tolerate only a few minutes ofhot water soaking (e.g., Leucaena); they must bequenched in cool water first before the long soak at

room temperature begins. Problems arise in: 1) stand-ardizing the technique, 2) maintaining precise controlof times and temperatures, and 3) treating large seedlots.

Soaking in water at or near freezing temperaturefor a few days to 2 weeks has expedited germinationof coniferous seeds; cold soaking is not successful forhard coated seeds on which acid scarification is used.Soaking probably leaches germination inhibitorsfrom seeds, softens hard but not impermeable seed-coats, or completes an imbibition requirement for ger-mination. For example, alternate-day soaking inwater, and night drying for 7 days before sowing in-creased the germination percentage of Terminaliaivorensis from 30 percent to as much as 70 percent inGhana (Il. Germination period for P. caribaea wasreduced by water-soaking seeds for 48 hours at roomtemperature (5 1.

8.2 Mechanical Scarification

Impermeable seedcoats can be broken mechanicallywith files, sandpaper, and electric needles for smalllots and with hand or motor-driven scariflers, such assandpaper-lined drums and cement mixers, for largelots. Germination tests are needed, as for acid scarifi-cation, to determine optimum treating time. One ver-ifies successful seed treatment by observing swellingafter water uptake or visual examination with a handlens. Overtreatment damages seeds by reducing ger-mination and increasing risk of fungal attack.

Advantages of mechanical scarification are: 1) lessrisk of injury to workers, 2) no need to control temper-ature, and 3) seeds remain dry throughout pretreat-ing, allowing immediate sowing afterwards. Disad-vantages are: 11 seeds are easily damaged byovertreatment, 2) scarified seeds are perhaps moreeasily damaged by pathogens than are nonscarifiedseeds, 3) large lots require special equipment, and 4)seeds with resins or fleshy pulp cannot be used insandpaper-lined tumblers.

8.3 Stratification-Methods

Besides seedcoat or “external dormancy,” some treeseeds have “internal dormancy.” Before such seedsgerminate they must undergo physiological changesin which the seed embryo develops. Cold, moist treat-ments that artificially cause these changes are calledstratification; they are also known as moistprechilling or afterripening treatments.

8.5.2 Cold Stratification. -In cold stratification,seeds are stored in a well-aerated medium such assphagnum moss and kept at low temperatures of 1” Cto 4°C for 2 to 4 months. Three precautions that mustbe taken are: 1) maintain adequate moisture that canbe imbibed by seeds throughout stratification; 2) keeptemperatures low, near freezing, to reduce microbial

35

activity, reduce sprouting, and prevent heat buildupfrom seed respiration; and 3) supply adequate aera-tion for gas and heat exchange, particularly for long-term stratification of 2 months and longer.

Figure 8-2.--Stratification can he done (A) for small seed lots byusing sealed plastic bags or (B) for large lots by using.sealed drums or similar containers.

Several techniques are used for stratification (7).Before subjecting any large seed lots to stratification,prior history of their need should be documented.Usually, small lots are split and germinated usingstratified and unstratified seeds through paired tests.

First, decide whether lot size is small enough forpretreating in small plastic bags or large enough forbags and drums (fig. 8-2). Seeds are brought to highmoisture content by water-soaking them overnight atroom temperature or up to 4 days for nut-like fruitsand pine seeds that have hard seedcoats. Using smalllots and different soaking periods establishes the bestsoaking time when no information is available.

Second, choose a moisture-holding medium such asgranulated peat moss, sphagnum moss, or sand. Peatmoss is often used because it is slightly acidic and,like sand, dispels heat well. The medium should bejust moist enough that squeezing with one’s fingersexpels some excess water.

Third, seeds are mixed with the treating medium.The entire mixture is placed in canvas bags in largedrums or boxes with drainage holes at the bottom (fig.8-2). If available, cracked ice is also mixed with themedium to assure rapid and uniform chilling. Smallseed lots are stored alone in plastic bags or with mossplaced over them. Seeds are always stored loosely,never packed. They can also be laid out on cheesecloth over moss in drums or boxes. If seeds and treat-ing medium are mixed in the same containers, acleaning and separating problem can occur whenstratification ends.

Drums and bags must be promptly closed to preventseeds and medium from drying out. Seeds andmedium are inspected every few days for adequatemoisture. If stratification is 30 days or longer, bagsshould be taken out and inspected for mold and dryingevery 2 weeks. When seeds are checked, they shouldalso be thoroughly turned and mixed. Freezing ofmoss at the top of bags can occur but is no cause foralarm; it only indicates that the medium is dryingrapidly and that additional moisture is needed. Pooraeration is indicated by an alcohol odor, a sign thatanaerobic respiration is taking place. If this occurs,seeds are checked more frequently by opening all bagsand turning the seeds. Recommended storage temper-ature is 1°C to 4°C.

At the end of the stratification period, seeds areremoved and washed. If seeds and medium were notmixed, washing may not be needed; washing removespotentially dangerous and damaging micro-organisms. Immediate sowing is recommended; ex-treme drying before use may induce a second dor-mancy in some species. Most southern pine seeds canbe stored under stratification for at least 1 year at 4°Cwithout loss of viability.

In temperate areas without cold storage facilities,outdoor stratifying pits are used. Seeds are thor-oughly mixed with sand and kept moist in pits 1 to

36

2 m deep over winter, Stratification occurs during thewinter. Where winters are milder, stratifying inaboveground beds exposed to more fluctuating tem-peratures accomplishes the same thing.

Some species in temperate areas require both warmand cold stratification prior to germination. Examplesare green and white ash (Fraxinus pennsylvanica andF. americana) and black cherry (Prunus serotina).Tropical examples are not documented.

8.3.2 Chemical Alternatiues. -Chemical meanshave been investigated to eliminate the need foreither cold or warm stratification. Inorganic ions, or-ganic acids, and growth regulators such as gibbere-llins have stimulated germination under laboratoryconditions (7). Germination of dormant and unstrati-fied Eucalyptus delegatensis , E . fastigata , and E . reg-nans was improved with application of gibberellicacid (2 ).

LITERATURE CITED

1. Brookman-Amissah, J. Seed problems as they af-fect forestry practice in Ghana. Paper 6. In: Pro-ceedings, international symposium on seed proc-essing. IUFRO Working Party S2.01.06. Bergen,Norway; 1973. 9 p. Vol. II.

2. Krugman, Stanley L.; Eucalyptus. In: Seeds ofwoody plants in the United States. Agric.Handb. 450. Washington, DC: U.S. Departmentof Agriculture, Forest Service; 1974. 1974: 384-392.

3. Little, C. H. A. Use of plant growth regulators inthe conifer nursery. In: Proceedings, northeast-ern area nurseryman’s conference. Halifax,Nova Scotia. Canada. Truro, Nova Scotia: NovaScotia Department of Lands and Forests; 1982:25-36.

4. Marrero, Jose. Tree seed from Puerto Rico.Caribbean Forester. 10: 11-36; 1949.

5. Matias, A. R.; Betancourt, A.; Zayas, A.; Pena, A.;Rivero, R. Forest seed in Cuba. Paper 31. In:Proceedings, international symposium on seedprocessing. IUFRO Working Party S2.01.06.Bergen, Norway: 1973. 13 p. Vol. II.

6. Sheikh, Malmood Iqbal. Tree seeds respond to acidscarification. Pakistan Journal of Forestry.29(4): 253-254; 1979.

7. United States Department of Agriculture, ForestService. Seeds of woody plants in the UnitedStates. Agric. Handb. 450. Washington, DC:U.S. Department of Agriculture, Forest Service;1974. 883 p.

8. Venator, C. R. Effect of gibberelic acid on germina-tion of low-vigor Honduras pine seeds. ForestScience. 18(4): 331; 1972.

CHAPTER 9

9. TRADITIONAL SEEDBED PREPARATIONAND SOWING

Traditional methods to produce nursery stock in-clude container (3, 5, 14, 15, 16,27,28,) and bare-root (I , 12,17,29) methods. Container methods aremost common because outplanted seedlings and cut-tings (25) with attached soil or other growth mediumsurvive well. Where countries use both methods, con-tainer systems were probably used first for organizedreforestation work. Because container methods canemploy many workers of either sex, they are gener-ally preferred in developing countries where jobs arescarce (18 1.

In this chapter, the general preparation and sowingtechniques for container and bare-root seedbeds aredescribed. Throughout this guide, seedbed is used in avery broad sense. It means ground-level and raisedbeds where seeds are sown 1) in or on top of the soil,2) in pots or containers where seeds are direct-seeded,and 3) in pots where seedlings are transplanted.Transplants are usually germinated in flats but canalso be produced in seedbeds. Appendix 9 givesspecific procedures for sowing, transplanting, andearly tending care of several plantation species.

9.1 Container Systems

9.1.1 Selection Criteria9.1 .l .l Advantages and Disadvantages. -Con-

tainer systems are used when reforestation conditionsare too harsh (usually too dry and too exposed) forsurvival of bare-root stock. Even on non-critical sites,potted seedlings have higher survival, and sometimesbetter growth, than bare-root stock. Advantages ofcontainer systems over bare-root systems are:. good soil is not necessarily needed at the nursery

site;. time in the nursery is shorter;. roots are not exposed to air and heat during trans-

port to the field;. faster growth initiation occurs after planting be-

cause transplant shock is less;. planting season can be extended because seedlings

are planted with moisture- and nutrient-holdingmedium around them; and

. start-up time for a new nursery is minimal.Disadvantages of container systems are:. they are generally more expensive and time con-

suming to produce;. bulky pots pose storage and transport problems;

37

l fewer seedlings per trip are transported to the field;0 seedling extraction from pots for repacking and

transport can be difficult;. much greater risk of root binding exists after out-

planting;. there is more potential damage to root systems if

seedlings are repacked for transport; and. a continual source of good potting medium is re-

1 quired.

9.1 .1.2 ShapelVolume Considerations.-Pot shapeand volume both directly influence seedling growthand development in containerized systems. Long potsallow longer and better developed root systems, whichare desirable for dry sites (26 ), and short pots producesmaller root systems, which are adequate for moistsites. Size also affects the amount of growth mediumneeded to fill pots and their holding time in the nurs-ery. Once the available pot root volume is filled,seedlings must be outplanted quickly or root strangu-lation and spiraling will occur (24 ). Large pots do notalways produce the most vigorous stock (4).

The ideal container will support growth of highquality seedlings in the shortest possible time. Forpines, this means growing seedlings 25 to 35 cm tallin 6 to 8 months, or, if they are “forced” with fertiliz-ers, 4 to 5 months. Too often, the ideal pot for physio-logical development is not available locally and coststoo much to import. The most common container usedis the plastic bag. It comes in many sizes and is easilymanufactured locally. If imported, costs are moderateto inexpensive, depending on freight distance. Darkplastic is best because, if overwatering occurs, algaland fungal growth are less prevalent in dark plasticthan in clear bags exposed to more light. In Tanzania,clear bags were reported better for P. oocarpa growth(22). Other pot types are clay, split bamboo, tarpaperpots, tin cans, and milk cartons.

9.1.2 Selecting and Preparing Pot Media.-Suit-able potting media are cheap, readily available mate-rials in the community and can be economically ob-tained from inside or outside the country.Alternatives are soil alone; soil/sand mixtures; or-ganic based mixtures with various proportions ofpeat, compost, sugarcane waste, rice hulls, sawdust,or ground bark; and synthetic mixtures (9, 13).

Soil alone and soil mixed with sand and organicmaterials are used most often. Usually, soil alone isundesirable because of its weight. If nothing else isavailable, sandy to sandy loam soil is best; heavyclays are undesirable because water drainage is poor.Alluvial soils are good if their texture is sandy loamto silt loam, but these soils in dry limestone regionsare often undesirable because of high clay content andhigh pH. Organic based mixtures are good becausethey are light and possess good texture, water-holdingcapacity, and nutrient retention.

3x

Precise ratios of sand, soil, and composts vary ac-cording to local materials used. Fertility, acidity, andphysical composition are all different for sand, silt,and clay soils and mixtures with or without soil. Al:3:l mixture of soil/river sand/decayed manure ororganic materials is a good starting point(Sec. 15.2.2.2). Growth is usually, but not always,poor with sand-only medium (7, IO,23 1.

All materials should be screened free of clods,stones, and other debris (fig. 9-l). Screened material,especially soil, can be sterilized but usually is not.When available, methyl bromide or other fumigantsare used rather than steam sterilization (fig. 9-2).Proper fumigant use is outlined in Appendix 9.

9.1.3 Filling Pots. -Metal or bamboo funnels helpdirect potting medium into containers. Potting tablesfor filling are very practical (fig. 9-11, especially whenlocated under a protective shed (fig. 4-3). Light tamp-ing against the ground or potting table helps settlematerial in plastic bags; overtamping should never bedone, especially for a medium of high clay content,because compacting reduces drainage and aerationand causes poor root development. Compacted soildoes not have improved moisture retention because ofgreater capillary pore space (8 ). Rigid-walled contain-ers can be filled with material shoveled from wheelbarrows, after lining-out the pots in beds. Excessmedium dropped between pots promotes weed growthin these interspaces. While some workers are fillingpots, others can be setting them out in neat lines androws (fig. 9-3).

9.1.4 Direct-Seeding Method.-Germination per-centage tests determine the amount of seeds sown(Chap. 7). Generally, about 20 percent more seeds aresown than the number of seedlings needed to allow fornatural mortality and culling in the nursery. Ap-pendix 9 has a specific example of determining theseeds needed for a production run.

Direct seeding is the placing of seeds on pottingmedium in pots. Large to medium-size seeds of pineand Gmelina are best suited for this method; smallseeds are not unless they are pelletized first. Advan-tages of direct seeding over transplanting are:9 it avoids additional steps of germinating in trays

and transplanting into containers; andl if two or three seeds are sown per container, the

number of “filled” containers (i.e., those with atleast one healthy seedling) is high.

After seeds are sown onto the container medium,they are usually covered with a light layer of soil,vermiculite, or rice hulls that protects them againstanimal predation and damage from irrigation water-drops. Direct seeding can be done manually or withmachines for round- and irregular-shaped seeds (6).Care must be used in culling excess direct-seededplants from pots to avoid damaging the root systemsof remaining seedlings (21).

EENED TO? SOIL

SOIL/MIXTURE SCREENING

FUNNEL NAOE OFOALVANIZED IRON

FUNNELS FOR FILLING BAGS, TUBES, OR OTHER CONTAINERS

P O T NEDIUY

THREE LEQQED

NON - MECHANICAL MECHANICALPOTTING TABLE POTTING TABLE

Figure 9-l.-Traditional containerized nursery techniques. Adapted from(32).

Figure g-P.-Fumigating soil in large pots with methyl bromideapplied under plastic sheeting.

9.1.5 Transplant Method

9.1.5.1 Germination Medium. -Possible germina-tion media for seed flats (fig. 9-4) are vermiculite,washed and sterilized river sand or sand/soil mix-tures, rice hulls, and tissue paper for very small seeds.Each has advantages and limitations (19).

9.1.5.1.a Sand/Soil.-A 1:l volume mixture ofwashed sand and soil is the most commonly used ger-minating medium because both are readily available.Soil and sand may also be used individually. Particlesize should be 21.7 mm but 12.4 mm, as determinedby sieve analysis. Particles of this size range do notcohere easily and therefore will not crust over andpuddle when water is added. Aeration and drainageproperties are also excellent for seedling emergenceand growth. Soil and sand used for germinating traysshould always be sterilized to prevent disease andweed growth (see Appendix 9).

9.1.5.1.b Rice Hulls.-In many countries, ricehulls are a cheap, local substitute for sand/soil or ver-miculite germination media. Unground rice hulls are

39

T-BAR SHADING SCREENS, USING PLASTIC (MAYA) MATERIAL;

PALM FRONDS OR BAMBOO KANA SCREENING COULD BE USED

STRAW OR REED MATS OVER POLES A LARGE SHADE TREE FOR TEMPORARY“‘FLYING” NURSERIES

Figure 9-3.-Nursery shading alternatives.

light, making moving and lifting of germination flatsquite easy. Their uneven and irregular packing inflats gives good aeration and drainage, and rice hullsdo not decompose during the germination period. Usu-ally, rice hulls are free of most weeds and pathogens;sterilization is used only when contamination is sus-pected.

9.1.5.l.c Vermiculite.-When available, vermi-culite is the ideal germination tray medium because:. it is sterile and free of pathogens;. particle size allows aeration and moisture reten-

tion;. reaction of the medium is essentially neutral (pH

7);. seedlings easily emerge from underneath a cover-

ing layer of the medium;. seedling root growth is unrestricted; and. seedlings are easily lifted at transplanting because

of the medium’s physical properties.

40Figure 9-4.--Standard galvanized metal germination flats

The major limitation in using vermiculite is cost,because it must be imported. Once used, the materialcan be resterilized and added to potting medium toincrease bulking properties (Sec. 15.2.1.2).

9.1.5.1.d Tissue Paper.-Eucalyptus and kadamseeds are very small and do not grow or transplantwell if placed directly on any of the above germinatingmedia. Seeding them first onto moistened tissue papersuch as Kimpak, which is used in laboratory work,improves germination. Paper color or type is irrele-vant as long as it is clean, light, and very porous.

Finally, all of these germinating media are used fortemporary physical support of the germinants; theyare not intended to support physiological growth forlong periods. Thus, fertilizers should neuer be appliedto any of them before germination. Seeds have suffi-cient nutrient reserves in their endosperm to germi-nate and grow for a few days until transplanted. Iffertilizers are applied, damping-off incidence is veryhigh!

9.1.5.2 Sowing and Germinating. -Germinationtrays are made from wood or metal. Galvanized metaltrays, approximately 30 by 45 by 8 cm, are common(fig. 9-4). After the trays are filled to within 4 to 6 cmof the top, the medium is smoothed and lightlytamped.

Seeds are placed on the prepared medium, then cov-ered with 6 to 10 mm of vermiculite, rice hulls, or fine

STEP I

v

POUR 3-Smm OFWATER INTO A CUP

STEP 2

MOISTEN NEEDLE OR THINSLIVER OF WOOD TO A

ff-

HElQHf NOT MORE THAN

. 3nm

STEP 3PLUNGE THE NEEDLE

INTO THE SEEDS;

SEEDS WILL STICKTO THE POINT

sterilized sand; these coverings allow better seedlingemergence than soil alone and protect seeds from an-imals. Sowing deeper than 6 to 10 mm below the sur-face prevents emergence (II 1. For small seeds (euca-lyptus and kadam), special sowing techniques areused (fig. 9-5). Mahogany and other large-wingedseeds are de-winged first, then laid flat on the germi-nation medium; pushing seed into the medium causesformation of J-roots (fig. 10-2).

Seeded trays are placed under 20- to 50-percentshade (fig. 9-6) and watered as needed. Shading meth-ods for small nurseries are simple or complex, usingmetal frames, wooden T-frames, and shade trees fortemporary “flying nurseries” (fig. 9-3).

Overwatering must be avoided to prevent damping-off. A simple test to determine if moisture in germina-tion medium is adequate is to squeeze a small portionof medium between thumb and forefinger. If watercan be squeezed out, no additional watering is needed.

9.2 Bare-Root Systems

9.2.1 Selection Criteria

9.2.1 .l Advantages and Disadvantages. -Bare-root nursery stock is produced by traditional labor-intensive and mechanized methods (Chap. 16).Species successfully grown by bare-root methods are

STEP 4

THE PIN INTO THEA7 A 45* ANGLE TOPTH NO GREATER

WATERING YETHOO

S T E P 5

TRANSPLANT SLEOLINBINTO EMPTY POT WHENTHE PLANTS ARE DETWL EN25 a 50 mm H I G H

ALTERNATEMETHOD MIX SEEDS WITK F I N E

SAND a WAKE ONTOCONTAINER OR RAISEDSEEDBEDS

/‘ir‘Jr,, S E E D S‘I

Figure 9-5.-Seeding very tiny seeds such as eucalypts or kadam. Adapted from (31).

41

S T E P I

FILL WITH SOIL;WATER TWOWEEKS BEFORE

LAY SEEDS

S T E P 3

S T E P 2

REMOVE ALLGERMINATED WEEDSPRIOR TO SEEDING

S T E P 4

COVER SEEDS ABOUTTHREE TIMES THEIRSMALLEST DIAMETER.WITH FINE SOIL

Figure 9-6.--Seeding procedures for medium and large seeds. The same technique can befollowed when seeding onto raised seedbeds. Adapted from (31).

most pines, teak, Gmelina, Casuarina, and kadam.Advantages of these systems over container systemsare:l sowing seeds directly in ground-level or raised beds

avoids transplanting after germination;l early and later tending care are usually easier:. there is less weight to transport from nursery to

field, allowing more seedlings per trip;. bundling, handling, and packing are fairly simple

for treatment; and. bare roots are the best type of stock for mechanized

planting.Disadvantages are:

nursery soils need inherently good physical andchemical properties for permanent use;

seedlings need 2 to 3 months more time for develop-ment;

damage is potentially greater to roots if they areexposed to air and heat after lifting; and

large amounts of high-quality irrigation water arerequired.

9.2.2 Bed Orientation. -Small, shaded bare-rootseedbeds in the tropics can run east/west but notnorth/south as- in temperate areas. Because tropical‘are& are close to the equator, the sun’s rays are moredirect there than in more northerly or southerly lati-tudes. An east/west orientation and covered beds (fig.A4-1, Appendix) under sloped roof sheds provideshade during the hottest part of the day for seedbeds.For large bare-root nurseries, available land and itstopography will dictate bed orientation.

9.2.3 Fallows.-Fallows or cover crops are grownon idle nursery land to protect against erosion and tobuild up soil organic matter. Bed areas that have beenin fallow should be plowed 4 to 6 months before sow-ing seeds. Allowing grass and weeds to decomposefirst before sowing reduces soil C/N levels to levelsthat do not limit seedling nutrition. A C/N ratio of3O:l or less avoids adding supplemental N fertilizers.Typical ratios based on dry weights of C and N arealfalfa, 13:l; legume-grass hay, 8O:l; oat straw, 8O:l;and sawdust, 25O:l.

9.2.4 Cultiuation. -Before cultivation, bed areascan be fumigated (Sec. 16.2); however, this is rarelydone in small nurseries. Beds are cultivated by handor implements pulled by horses, oxen, mules, andtractors. Hand cultivation is limited to beds 5 m orshorter (fig. 9-7). Raised beds with protective coveringare also used (fig. 9-8). Standard beds are 1.2 m wide,with seven seedling rows. Within beds, soil can bemounded (fig. 9-9) with hand tools or special plows.Mounding has several advantages, primarily in-creased aeration and drainage (2) (Sec. 16.1.3). Walk-ways should be at least 45 cm wide between nurserybeds to allow easy access for weeding and protectioncontrol.

9.2.5 Sowing. -Push-type planters or seeders candrill seeds and fertilizers to specified depths at thesame time and cover both in one operation. For smallbeds, furrows are dug along string and stake guides.Seeds are covered to a depth 1 or 2 times their width.Fertilizers are placed alongside or underneath seeds,with an intervening layer of soil in-between; if fertil-

42

izers touch seeds or new roots, burning of plant tissueOCCURS, probably resulting in see!nling mortality.Sometimes, seeds are broadcast (direct-seeded) overseedbeds by hand or with cyclone broadcast seeders.Average density is 150-300 seedlings/m2 (20, 30).

9.2.6 Mulching. -After seeding, mulches arespread over seedbeds to protect the seeds from ani-

mals, erosion hazards, and weeds, and to conserve soilmoisture. Many kinds of mulch are used; none muststop germinating seeds from pushing upward to thesurface or rot on top of the seedbeds (Sec. 16.3.3).Mulching may or may not influence seedling survivalin the nursery through outplanting time (22 1.

Figure 9-‘I.-Proper method of laying-out small, ground-level seedbeds for bare-root nursery stock.

43

A. RAISED NURSERY BED KANA SCREEN

THICK WOOD

ODEN SUPPORTS

6. SUNKEN BED FOR CONTAINER PLANTS

IRON ROOF

WIRE SUPPORFOR SHEETIN

OLYETHYLENE

C. COVERED SHED

POTTINGCONTAINERSa MATERIALS

SAND WORKBENCH/WATER TAP

POTTINGUJ TOP SOIL

Figure 9-R-Nursery structures. Diagrams A and B by A. Krochmal, USDA Forest Service, retired, Asheville, NC; diagram C adapted from(32).

44

RAISED

SIDE V IEW

TOP VIEW

A. RAISED SEEDBED FOR OVERHEAD IRRIGATION.

DAILY RLOUIREYENT:

1.2. 7.0 I 0.02 s O.l7n3= ITOL OR APPR

44 GALLONS

AT 7 ROWS (L Scm INTERVALS, THISBED CONTAINS 700 TREES

OPEN ROOTED. STOCK

B. WATER NEED CALCULATIONS.

Figure 9-9.-Nursery bed irrigation considerations. Adapted from (31).

LITERATURE CITED

1. Barres, H. Rooting media for growing pineseedlings in hydroponic culture. Res. NoteITF-2. Rio Piedras, PR: U.S. Department ofAgriculture, Forest Service, Institute of Tropi-cal Forestry; 1964. 4 p.

2. Garcia, A.; Miguel, H. Nursery trials in the con-cession, Bajo &lima, during 1975-76. ForestryResearch Report 22. Carton de Colombia, S.A.Cali, Colombia; 1977. 4 p.

3. Geary, T. F.; Avila Cortes, G.; Hadley, H. H. Ger-mination and growth of,Pinus caribaea directlysown into containers as influenced by shade,phosphate, and captan. Turrialba. 21(3): 336-342; 1971.

4. Ghosh, R. C.; Bakhshish, Singh; Sharma, K. K.Suitability and economics of bag size for raising

seedlings of Pinus patula and Pinus caribaea.The Indian Forester. 10302): 773-786; 1977.

5. Holmes, D. A.; Floyd, A. G. Nursery techniquesfor raising eucalypts in jiffy pots on the NewSouth Wales North Coast. Res. Note 22. NewSouth Wales, Sydney: Department of Conserva-tion, Forestry Commission; 1969. 15 p.

6. Howcroft, N. H. S. A direct sowing technique forPi&s. Tropical Forestry Res. Notes S.R. 4. Bu-1010, Papua, New Guinea: Department ofForests; 1973. 9 p.

7. Jackson, J. K. Nursery techniques in the Sa-vanna region of Nigeria. Ministry of Agricul-ture and Natural Resources Res. Pap. 32.Ibadan, Federal Republic of Nigeria: FederalDepartment of Forest Research; 1974. 8 p.

8. Khan, M. A. Waheed. Improved methods anddevices in nursery practice. Forestry and Edu-cation Project Pamphlet 28. Soba-Khartoum,

45

I-

Republic of Sudan: Forests Department andUnited Nations Development Programme;1966. 11 p.

9. Lowe, R. G. A tropical medium for tree species.Tebh. Note 37. Ibadan, Federal Republic ofNigeria: Department of Forest Research; 1967.8 P.

10. Maghembe, Jumanne A.; Lulandala, Luther L. L.Effect of different potting mixtures and nutri-ent treatments on the survival and growth ofPinus caribaea seedlings. Record 16. Morogoro,Tanzania: Division of Forestry, Faculty of Agri-culture, Forestry and Veterinary Science, Uni-versity of Dar es Salaam; 1980. 20 p. i

11. Marrero, Jose. The proper depth and kind of cov-ering for seeds of several tropical hardwoods.Caribbean Forester. 8(3): 213-236; 1947.

12. Marreso, Jose. Forest planting in the CaribbeanNational Forest, past experience as a guide forthe future. Caribbean Forester. 9: 95-213;1948.

13. Marrero, J. Sphagnum moss as a medium for root-ing cpine seedlings. Trop. For. Notes 7. RioPiedras, PR: U.S. Department of Agriculture,Forest Service, Institute of Tropical Forestry;1961. 2 p.

14. Marrero, J. Practicas usadas en 10s viveros depines: de Puerto Rico. Caribbean Forester,23(2)! 87-99; 1962.

15. Marrero, Jose. Effect of plastic mulch on weedgrowth and early height growth of Honduraspine. Res. Note ITF4. Rio Piedras, PR: U.S.Department of Agriculture, Forest Service, In-stitute of Tropical Forestry; 1965. 5 p.

16. Marrero, Jose. Potting media for Honduras pine.Res. Note ITF-5. Rio Piedras, PR: U.S. Depart-ment of Agriculture, Forest Service, Instituteof Tropical Forestry; 1965. 5 p.

17. Monteith, D. 3.; Ybarra-Coronado, R. Survival ofbare-rooted Honduras pine in Puerto Rico. Tur-rialba. 19(2): 291,-292; 1969.

18. Nay, W. B. Nursery notes to remember. Nairobi,Kenya: East Africa Agriculture and ForestryResearch Organization; 1957. 9 p.

19. Rai, S. N. Nursery and planting of some tropicalevergreen and semievergreen species. India:Government of Karnataka; 1979. 50 p.

20. Rowan, Samuel J. Seedbed density affects per-formance of slash and loblolly pine in Georgia.In: South, David B., ed. Proceedings, interna-tional symposium on nursery managementpractices for the southern pines; 1985 August4-9; Montgomery, AL. Auburn, AL: School ofForestry, Alabama Agricultural;’ ExperimentStation, Auburn University; 1985: 126-135.

21. Solberg, Karl H. Direct sowing contra transplant-ing in the nursery. Pinus caribaea and P.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

oocarpu , Tanzania. EAC/NORAD Lowland af-forestation project Tech. Rep. 7. Aas, Norway:Department of Silviculture, Agricultural Uni-versity of Norway (NLH); 1978. 8 p.

Solberg, Karl H. Miscellaneous nursery experi-ments. Pinus caribaea and P. oocarpa , Tanza-nia. EACIMORAD Lowland afforestation proj-ect Tech. Rep. 8. Aas, Norway: Department ofSilviculture, Agricultural University of Nor-why (NLH); 1978. 33 p.

Solberg, Karl H. Three nursery experiments withfertilization and potting soils. Pinus caribaeaand P. oocarpa, Tanzania. EACNORAD af-forestation project Tech. Rep. 4. Aas, Norway:Department of Silviculture, Agricultural Uni-versity of Norway (NLH); 1978. 53 p.

Solberg, Karl H. Tube size and plant age. Nurseryand field experiment. Pinus caribaea andP .‘oocarpa, Tanzania. EAC/NORAD afforesta-tion project Tech. Rep. 10. Aas, Norway: De-partment of Silviculture, Agricultural Univer-sity of Norway (NLH); 1978. 34 p.

Som sundaram, T. R.; Jagadees, Stanley,S.tropagation of Casuarinu equisetifoliu Forst.by planting shoots. The Indian Forester.103(11): 735-738; 1977.

Theron, J. M. Nursery research in Malawi 1964-1971. Research Record 56. Zomba: MalawiForest Research Institute; 1972. 43 p.

Venator, C. R.; Munoz, J. E. Containerized treeprqduction in the tropics. In: Tinus, Richard W.;Stein, William I.; Balmer, William E., eds. Pro-ceedings, North American containerized foresttree seedling symposium; 1974 August; Den-ver, CO. Great Plains Agriculture Council Pub.68iWashington, DC: Great Plains AgricultureCouncil; 1975: 334-335.

Voorhoeve, A. G.; Weelderen, A. W. H. Nurserypractice of Pinus caribaea. Paramaribo: Suri-nam Forest Service, Research Branch, 1968.20 p.

Wadsworth, Frank H.; Marrero, Jose. The signifi-cance to Puerto Rico of Companhia Paulista ex-perience with Eucalyptus. Caribbean Forester.14$-2): 65-78, 1953.

Ward, D.; Johnston, T. N. Determination of opti-mum seedling density for bare-root HondurasCaribbean pine. In: South, David B., ed. Pro-ceedjngs, international symposium on nurserymanagement practices for the southern pines;1985 August 4-9; Montgomery, AL. Auburn,AL: School of Forestry, Alabama AgriculturalExperiment Station, Auburn University; 1985:118-125.

Weber, Fred R. Reforestation in arid lands. PeaceCorps/Vita Publications Manual Series 37E.Washington, DC: Government Printing Office;1977. 248 p.

46

32. W&l&, II. J., camp. Manual of reforestation anderosion control for the Philippines. Eachborn,Germany: Agency for Technical Cooperation,Ltd. (GTZ); 1975. 569 p.

\

CHAPTER 10

10. TRADITIONAL EARLY TENDING OFSEEDBEDS AND CONTAINERS . ,

Container and bare-root systems have similar ear,Zytending requirements for water, shade, and weedirig;early tending includes the first 4 to 6 weeks bfseedling growth, including germination. Containersystems may be more complex if they include addi-tional steps of transplanting and associated activities.Throughout this discussion it is assumed that ade-quate protection, pest control, and nutritional needsare monitored (Chaps. 12 and 13).


10.1 .I Transplanting

10.1 .I .I Timing. -When transplanting from ger-mination trays, it is essential to avoid stunting ofseedlings. Transplanting is done after seedlings are

large enough to be handled safely but before they gettoo large and crowded in the trays. The optimum timeto transplant pine germinants is 3 to 6 days afteremergence and before the seedcoat is thrown (11).

For kadam and Eucalyptus species, seedlings mustbe at least 2 cm tall or have four or more leaves thatare large enough to handle. Because kadam plants arevery small, seedbeds are checked daily to find possibletransplants.

Early lifting after germination serves two purposes.First, seedlings are lifted before tap roots develop lat-eral branches. If lateral roots are stripped off oldertransplants, lost water absorption capacity causeswilting and maybe death. Second, large root systemsare easily bent during transplanting, causing devel-opment of J-roots (figs. 10-l and 10-21.

Transplanting into lined-out pots has two advan-tages over direct seeding in pots (3). First, managersdo not have to wait several weeks to see if seedlingdensity is satisfactory; workers control density inlined-out pots by transplanting one healthy seedlingin each pot. Second, once seedlings are ready for lift-ing, transplanting can be staggered over severalweeks or days. This procedure allows grouping trans-plants by similar age classes so that outplanting isalso spread over a longer period. When bulked seeds ofseveral provenances are used, germination may beuneven because of differences in germination rates(10). If this occurs, transplanting delays are the onlyalternative.

Figure lo-l.-Typical J-root systems on Swietenia (mahogany) caused by improper trknsplantingfrom germination trays into pots.

47

S T E P I S T E P 2

CONTAINERS

LIFT OUT SEEDLINGS FROM POTSOR SEED TRAY MEDIA WITH STICK

S T E P 3

PRICK SMALL HOLE IN CENTEROF POT OR CONTAINER CAVITYWITH SHARPENED STICK, DOWL,OR PENCIL.

S T E P 5

FIRM UP SEEDLING 8 EXPEL AIR FROM HOLEBY PUTTING STICK NEXT TO HOLE 8 PUSHINGSOIL TOWARDS SEEDLING.

PLACE SMALL SEEDLING BUNDLE IN BOWLOF WATER TO KEEP ROOTS MOIST; IFNECESSARY TRIM ROOTS WITH SCISSORST O 3 - 5 c m L E N G T H .

S T E P 4

NOT

PLACE SEEDLING IN HOLE; MAKE SUREROOT SYSTEM IS FULLY EXTENDEDLENGTHWISE, NOT DOUBLED OVER IN-m---mJ -SHAPE

AFTER FIRMING UP,REMOVE STICK 8FILL HOLE

Figure lo-2.-Transplanting or pricking-out procedures.

4 8

1O.f .I.2 Procedures. -Seedling roots must be keptmoist throughout the transplanting process to avoiddesiccation and death. Workers “prick-out”appropriate-size seedlings from germination traysand place them in a small container of water. Afterpoking a small hole in the soil (with pencil, nail, orsharpened stick), seedlings are placed in this hole.The soil is then carefully firmed up around eachseedling, eliminating air pockets in the root area.Firming up seedlings and closing air pockets is doneby 1) putting the planting dibble alongside theseedling and 2) pushing soil towards the seedling tofill the cavity (fig. 10-2). One laborer can transplantabout 4,000 seedlings per day; if laborers work inpairs, they may plant up to 10,000 per day.

A risk in lifting several hundred seedlings fromdifferent germination trays and placing them in acommon bowl of water to avoid root desiccation is thespreading of damping-off and other fungal diseases (5,6). Submerging infected seedlings in a bowl of wateralong with other seedlings spreads the disease. Thereare several solutions. One is instructing trained work-ers not to place seedlings with suspected infection inthe transplant dish. Another safer solution is fillingthe transplant dish with a captan solution. Thus, eachseedling is treated with captan, minimizing spread ofinfection during transplanting. Once damping-off isnoticed, the treatments shown in table 10-l and theprecautions given in Appendix-12 are followed.

Another alternative is transplanting seedlings di-rectly from germination trays into pots, avoiding the

Table lo-l.-Treatments to prevent darnpiag:off

use of transplant dishes. This is not usually done fortwo reasons. First, germination trays are frequentlyfilled with heavy soil or soil mixes, making trays dif-ficult to lift and handle. If a tray is dropped, hundredsto thousands of germinants are lost. Second, wetseedling roots plant better than those coming directlyfrom germination trays.

10.1.2 Resowing. -If germination in direct seedingis unsatisfactory (i.e., many empty containers re-main), then containers are resowed. When resowing,containers with seedlings are grouped together in onearea, and those without seedlings are grouped in an-other area of the nursery. Regrouping pots before re-sowing avoids suppression of young germinants byolder germinants from the previous sowing. Excesstransplants should be put in’ separate beds. If voidsappear in some beds, they are filled immediately withthese extra seedbed transplants. This practice mini-mizes seedling growth differences among beds andgroups seedlings of the same age.

10.1.3 Watering. -Maintaining adequate but notexcessive moisture is essential during germination(2 1. Germination trays should be checked two to threetimes a day; if the medium is moist to fingers butwater cannot be extracted by squeezing, moisture isadequate. A fine (mist) spray from overhead pipes orback pumps prevents washing seeds out of the trays(41. If overwatering occurs, shade is removed tempo-rarily to speed up evaporation.

Some managers water seedlings immediately aftertransplanting; added water fills air pockets aroundthe seedlings (fig. 10-2). Small squeeze-water bottles

Type of treatment Point of treatment

A. Steam sterilization (before seeding)B. Fumigation (before seeding):

1. Methyl bromide gas2. Phosphine3. Ethylene dichloride4. Carbon tetrachloride5. Carbon disulfide

6. Drenches (a&r germination/transplanting):

1. Dexon2. Captan3. Ferbam4. Thiram5. Zineb6 . Chloroneb7. Bordeaux

Seeds

NO

N oYC?SN oYesYes

N O

N oN O

N oNON oN o

Germination medium

Y&3YesYeSNON o

YesYesYesYesYesYesYes

D. Dust (after transplanting):

1. Mercury2. Captan

YeSYes

N oN o

49

with a long spout are suitable for this operation. Over-watering creates a soupy mixture in a pot and shouldbe avoided to allow adequate aeration of roots (9).Fear that heavy rains will damage or wash out youngseedlings seems unjustified. In Puerto Rico, signifi-cant seedling losses due to rainfall have never beenseen, even after severe downpours.

20.1.4 Shade. -Transplanted seedlings should beplaced under at least 30-percent shade for 1 to 2weeks; some areas use up to 85-percent shade (7).Although it is possible to transplant Pinus caribaeuinto sun-exposed containers and obtain high survival,this practice is not recommended. Because seedlingssuffer the double shock of removal from shaded germi-nation beds and planting in exposed containers, riskof wilting and death is too great.

For raised transplant beds, shade screens are placedhigh enough above the pots so that workers have ac-cess for tending seedlings (fig. A4-1, Appendix). Forground level beds, posts and T-frame structures arescreened to similar specifications (fig. 9-3).

Saran (open-mesh plastic sheeting) shade cloth is

expensive but quite resistant to damage from ultravi-olet sunlight. With proper handling and storage afteruse, Saran can last 10 years. Other shade materialsare bamboo (kana) screens, palm fronds, and woodenlaths.

Small seedbeds can have 20 to 30 percent shadecover for the first month. In open and sunny areas,shade is then gradually removed as seedlings becomeolder to avoid undue stress by sudden exposure tosunlight. Some large direct-seeded containerized op-erations use no shading unless transplants are used tofill in voids in seedbeds.

Treated wood frames and corner posts last longerthan untreated wood. If hot-cold treated wood is used,is must be dried properly before use so that preserva-tive chemicals do not “bleed” onto seedlings belowthem; such chemicals are toxic to plants and man.

To avoid edge effects by exposure to sunlight, Saranand other shade materials should extend 0.3 to 0.5 mbeyond bed borders. Early and late in the day, sun-rays are best blocked by dropping screens at ends ofthe beds. As explained in Chapter 4, greater shadeextension is needed on the south side of nursery bedsthan on the north side in lower tropical latitudes.

Figure lo-3.-Early weeding can be done by hand from both sides of small nursery beds for either CA) bare-root (Cordia) or fB) containerized(Araucaria) stock.

5 0

10.1.5 Weeding. -Only maintenance weeding isneeded in the early weeks after transplanting anddirect seeding in pots. Hand weeding is most common.Weeding frequency depends on whether the potmedium was sterilized, the extent of viable weed seedin the potting medium used, and the absence or pres-ence of nearby weed and grass seed sources.

Weeds must be pulled when they are small, young,and succulent, before their root systems develop toomuch. When weed roots have spread too far withinpots, removing them disturbs seedling roots(fig. 16-2). If workers are not careful, entire seedlingsare easily pulled out with weeds. When this occurs, itis almost impossible to replant 4- to 6-week-oldseedlings without causing deformed roots.


10.2.1 Watering. -Bare-root seedlings are moregenerally exposed to air and light than containerstock. Thus, water needs of unscreened bare-rootstock are greater than those of screened containerstock (I). Beds are checked frequently for moistureand signs of seedlings wilting. Approximately 100liters of water are needed daily for a bare-root bed 1.2by 5 m in size (fig. 9-9). Actual water needs vary bysite and are related to bed soil texture, amount ofsolar radiation received, presence or absence of winds,species transpiration rate, and growth stage ofseedlings (Sec. 16.4.21.

For medium and large bare-root nurseries, fixedirrigation systems give best water coverage 03). Forsmall nurseries, water hoses and sprinkling cans maysuffice. With any system, water should be applied asdroplets; continuous streams of water wash out youngseedlings. On high clay soils, overwatering causesroot rot due to soil moisture retention.

20.2.2 Shade.-Saran or lath shade can be pro-vided for small ground-level and raised bare-rootbeds. This technique is impractical for large mecha-nized operations (Chap. 16). Shading guidelines fortraditional bare-root and container nurseries are es-sentially similar (Sec. 10.1.4).

20.2.3 Weeding. -Guides for weeding traditionalbare-root and container beds are also similar (Sec.10.15). Hand weeding is practical when beds aresmall and labor is plentiful and cheap (fig. 10-3).When seasonal production in bare-root nurseriesreaches 100 to 200 thousand plants, chemical controlmay be more practical and economical. The major con-cern is selecting herbicides for weeds that are non-toxic to seedlings. Suitable herbicides and precau-tions to be followed are given in Appendix 12.

LITERATURE CITED

1. Baur, C. N. Nursery spacing and grading of slashpine seedlings. Division of Forest Management,Forestry Commission of New South Wales. Re-search Note 5; 1960. 7 p.

2. Day, R. J.!Water management. In: Duryea, MaryL.; Landis, Thomas D., eds. Forest nurserymanual: production of bare-root seedlings. TheHague, The Netherlands: Martinus Nijhoff/DrW. Junk Pub.; Corvallis, OR: Forest ResearchLaboratdry, Oregon State University; 1984:93-105.

3. Faulkner, R. Procedures used for progeny-testingin Britain with special reference to forest nurs-ery practice. Forestry Commission ForestRecord 60. London: Her Majesty’s StationeryOffke; 1967. 22 p.

4. Fishwick, R. W. Irrigated nursery practice in-struction. Kaduna, Northern Nigeria: Ministryof Animal and Forest Resources; 1966. 19 p.

5. Gibson, I. A. S. Damping-off in forest nurseries.Mycological Note 35. Nairobi, Kenya: EastAfrican Agriculture and Forestry Research Or-ganization; 1954. 3 p.

6. Hocking, D. Damping-off in pine nurseries. 4.Fungi associated with diseased and healthyseedlings and with seed. Mycological Note 42.Nairobi, Kenya: East African Agriculture andForestry Research Organization; 1966. 7 p.

7. Howcroft, N. H. S. A direct sowing technique forPinus. Tropical Forestry Research Notes S.R. 4.Bulolo, Papua, New Guinea: Department ofForests; 1973. 9 p.

8. McDonald, S. E. Irrigation in forest-tree nurs-eries: monitoring and effects on seedlinggrowth. In: Duryea, Mary L.; Landis, ThomasD., eds. Forest nursery manual: production ofbare-root seedlings. The Hague, The Nether-lands: Martinus Nijhoff/Dr W. Junk Pub.; Cor-vallis, OR: F,orest Research Laboratory, Oregon

. State Univetsity; 1984: 107-121.9. Solberg, Karl H. Miscellaneous nursery experi-

ments. Pinus caribuea and P. oocarpa, Tanza-nia. EACNORAD lowland afforestation projectTech. Rep. 8, Aas, Norway: Department of Sil-viculture, Agricultural University of Norway(NLH); 1978.33 p.

10. Solberg, Karl H. Tube size and plant age. Nurseryand field experiment. Pinus caribaea andP. oocarpa, ‘Tanzania. EACNORAD lowlandafforestation project Tech. Rep. lo., Aas, Nor-way: Department of Silviculture, AgriculturalUniversity of Norway (NLH); 1978. 34 p.

11. Venator, C. R.,The relationship between seedlingheight and date of germination in Pinus carib-sea var. hvndurensis. Turrialba. 23(4): 473-474; 1973.

51

CHAPTER 11

11. TRADITIONAL LATER TENDING OFSEEDBEDS AND CONTAINERS

“Later tending” includes the time from 4 to 6 weeksafter germination until lifting and outplanting. Thisperiod is distinct from that of early tending; seedlingshave passed the “hurdles” of germination and trans-planting and are well on their way to becominghealthy, plantable stock. Some hurdles involvingweeds, moisture, and lifting still remain. These fac-tors are now addressed, as well as more special stepsthat promote proper seedling shoot and root growth.As in Chapter 10, it is assumed that protection, pestcontrol, and nutritional monitoring continue simulta-neously (Chaps. 12 and 13).


11.1.1 Grouping, Sizing, and Lining-Out. -Nurs-eries must produce healthy seedlings having minimal

differences in height, root collar diameter, and foliagecharacteristics. In container systems, sorting orgrouping seedlings in beds by height produces plant-ing stock of uniform height. In bare-root systems,such sorting is impossible and uniform size isachieved by other means (e.g., undercutting, rootpruning, clipping), which are discussed in Sections11.2.4, 16.4.6, and 16.4.7.

Where labor costs are low, seedlings are regroupedas many as three times during their 6- to g-monthstay in the nursery. Because the practice creates em-ployment, it is defended in areas with high unemploy-ment and low labor costs; the reverse is true for areaswith high Iabor costs. Periodic regrouping culls infe-rior stock; this practice reduces lifting and packingchores later and probably reduces disease risk. Simi-lar regrouping is impossible for individual plants inmulti-cavity block containers but is possible for singlecell design systems (Sec. 151.6).

Potted seedlings can be lined-out on the ground oron other surfaces (figs. 9-3 and 11-l) and in perma-nent raised or sunken beds (fig. 9-8). Raising pots onblocks and wire screens fosters air pruning of roots.Placing containers on hard flooring or on plastic

NATURAL ROOT PRUNING OPTIONS

SILL1

PRUNING CONTAINER GROWN PLANTSROOT PRUYIYG

PRUNING SHEARS

-5Ji-$j~~~‘5

ROOT PRUNING WITWTROWEL on Y4CllETE

ROOT PRUNINGSEVERAL SEEDLINGS1 ONCE WIltI

5CISSDRS

0” WIT&l01 l GUNING EACH YACIIETE DN

1~JlVlDUAL ?LANT WITH WOODEN GLDCK

PRUNING SnEARS,W’ 1

PRUNING BARE-ROOT GROWTH PLANTS

Figure 11-l.-Lining-out, pruning, and lifting of container seedlings.Adapted from (20).

52

~hmting prevents root egress into soil under pots. Ifroots egress into underlying soil, lifting and packingare difficult and root damage from stripping is likely.

11.1.2 Inoculation with Mgcorrhizal Fungi.-Thefunction of mycorrhizal fungi on conifer roots is stillunder study. They appear to help in mineral (II 1 andpossibly water uptake, perhaps by increasing root sur-face area. The fact that pines do not grow withoutmycorrhizal fungi has been documented in PuertoRico (3, 18) and Venezuela (7). Thus, all coniferseedlings should be inoculated in the nursery. Mycor-rhizal fungi can be added to pot medium before trans-planting or 3 to 4 weeks after transplanting. Thisschedule avoids treating seedlings still in transplantshock but assures effective inoculation before olderseedlings have greater moisture and nutrient require-ments.

Mycorrhizal fungi can be sometimes obtained lo-cally or, if not, must be imported. They are collected induff and mineral soil (0 to 2 cm) from a healthy plan-tation or forest. All material is ground and incorpo-rated into the pot medium. An alternate method is toleach fungal spores from duff material with ambient-temperature water. Water and spores are applied tocontainers from sprinkling cans or back-pumpsprayers. Water temperatures that are too warm(>3O”C) can retard fungal growth and seedling devel-opment (12). After 2 to 4 weeks, mycorrhizal fungishould be visible to the naked eye or with a hand lens.

11.1.3 Watering. -Seedlings should be watered asneeded. This is determined by inspecting pottingmedium for moisture and by checking for wilting ofseedlings. Only combined knowledge and practical ex-perience with plant stress, different pot volumes andmedium used, time since last rainfall or irrigation,current moisture status of potting medium, andgrowth seedling stage will determine actual wateringschedules. Early morning watering is best. By after-noon, excess moisture on seedling foliage has evapo-rated, thereby reducing chance of disease, which canbuild up on moist foliage during warm, humid tropicalnights.

As seedlings grow and root systems expand in thepot medium, moisture status is dependent on con-tainer volume, type and texture of growing medium,and ability of pots to void excess water through drainports. Packed clay soil will not allow water to drainnormally throughout the pot. Thus, the medium maybe too dry or too wet, depending on how much wateris applied. In general, for many pot mixes, if too littlewater is applied, most of it runs off without infiltrat-ing. Overwatering saturates the medium and aera-tion is reduced.

Indications of poor drainage and aeration arestunted, yellowish-colored seedling foliage and moreconcentrated root growth between soil and bag inter-faces than in the pot medium. In extreme cases,

seedlings die because root rot has destroyed the roots(fig. 11-2). If foliage is only yellow, reducing wateringfrequency and respacing pots to expose them to moresun and drying may help. When foliage turns brown,seedlings are not salvable. New seedlings need a bet-ter drained medium and less frequent watering.

Salinity and acidity should be monitored regularly,particularly if nutrients are added with irrigationwater (Sec. 15.4.6.1). During hardening-off, wateringfrequency is gradually, then rigorously reduced @ec.11.3.2).

11.1.4 Weeding.-As seedlings grow, increasingfoliage area shades the pot surfaces and helps sup-press weed growth. Once weeds are established, theymust be removed cautiously (Sec. 10.15). Usually,hand weeding suffices. Problem areas are edge rows,particularly for ground-level beds. Unchecked weedgrowth in these areas shades out adjacent seedlings orprovides seed sources for nearby containers. Ma-chetes, shovels, hoes, and other small hand tools areused to remove grass and weeds from bed borders.

11.1.5 Shoot and Root Growth Control.-For con-tainer systems, shoot growth control is achievedmainly by grouping seedlings of similar height in thesame beds (Sec. 11.1.1). This practice keeps fast-growing seedlings from overtopping and shading outslow-growing ones. If limited overtopping of seedlingsoccurs and neither additional regrouping nor out-planting are imminent, the fastest growing individu-als can be clipped back. This slows top growth andenhances root growth. There must be sufficient potvolume to accommodate extra root growth or root spi-raling will result.

Root growth of potted seedlings is controlled by ef-fective pot volume and depth. Once roots fill this vol-ume and reach the pot bottom, seedlings must be out-

Figure 11-2.-Effect of overwatering and poor drainage on pottednursery seedlings.

53

planted. Extra holding time causes root spiraling orstrangling. Knowing seedling shoot and root growthrates and outplanting dates are crucial for selectingoptimum pot volume and for controlling root andshoot growth.

If unforeseen difficulties delay outplanting beyond1 to 2 months, two alternatives exist for “holdingover” seedlings. If labor is cheap and abundant,seedlings are repotted into larger containers that willaccommodate larger root systems. When repotting isnot feasible, severe root pruning is needed before out-planting. In both instances, survival and growth per-formance of hold-over seedlings in the field will prob-ably be less than that of seedlings planted on time.

11.1.6 Lifting and Transporting. -Root systems ofcontainerized stock are self%ontained and protectedby pot walls. Fewer precautions are needed in liftingand transporting containerized stock than are neededfor bare-root stock. If roots have grown through potbottoms, they must be pruned and trimmed beforeloading (fig. 11-l).

Containers are placed in transport flats, loaded ontotrucks, and securely tied (fig. 11-3). Because windburn is a real threat to seedlings, truck beds are en-tirely enclosed with a tarp to protect them from windand sun. Drivers should inspect tarp fastenings occa-sionally, making sure they are secure and that windis not blowing on seedlings.

A 5- to 8-cm head space between each layer ofseedlings is left on the truck beds. If light-weightgrowth medium is used; several tiers can be loaded ontrucks without creating a topheavy load. But if thepotting medium is soil; fewer tiers are possible be-cause greater weight can create a topheavy condition,endangering truck and driver when maneuvering1scurves.

In temperate climates, anti-transpirants are some-times sprayed on seedling foliage before transportingthem. Use of anti-transpirants is not usually neces-sary for seedlings in the tropics because they are notstored as dormant stock. Yet, if seedling tops are toolarge in relation to container root volumes and there

/ R O L L O F SHEETINQ

REPACK SEEOLINQS IN PLASTICSHEEflNQ WITH TEAR-AWAYPACKETS

SEEDLlNQS IN STYROFOAMMULTICAVITY CONTAINER

TARP OR COVER

KEEP TRANSPORT VEHICLE COVEREDWITH TARP OR SHEET TO AVOID SUNOAYAGE AND REDUCE TRANSPIRATIONLOSS B Y WIN0

SEEDLINQ TRANSPORT TRUCK

+ 7 0 c m .-I

WOOOEN CARRYINQ TRAY

PLANT IMMEDIATELY AT SITE OR “HEEL IN” WITHINTRENCH IF PLANTINQ MUST SE DELAYED

Figure 1 l-3.-Transporting of nursery seedlings to fold outplanting sites.

54

ic, dnngor ofexcessive tranf2piqation, anti-transpirahtscould possibly be used to reduce short-term water loss.Small research trials will determine the effectivenessof such treatment.


11.2.1 Inoculation. -Seedlings in bare-root bedsare inoculated with mycorrhizal fungi, using forestduff and mineral soil or water-borne spores, followingprocedures used for container beds (Sec. 11.1.2). Inoc-ulation is done before sowing or before seedlings are 4to 6 weeks old. If healthy plantations exist aroundbare-root beds (fig. ll-4), natural inoculation may beadequate, especially when bed soil is not sterilized.

11.2.2 Watering. -Generally, bare-root beds havegreater water needs than container beds because oftheir greater environmental exposure (Sec. 10.2.1).Older bare-root seedlings have greater water needsthan younger seedlings. Thus, almost daily wateringis required until hardening-off is started. Soil mois-ture must be checked often in well-drained, porousbeds. Bed soils with more clay lose moisture lessrapidly.

Damaging effects of irrigation droplet impact areminimal for older, larger seedlings. Exceptions areleaky pipes where escaping water can destroy largeareas of beds and seedlings (fig. 16-4).

21.2.3 Weeding. -Openness of bare-root beds fa-vors more weed growth than do container beds. Hand

weeding suffkes for small nurseries; mulches are usu-ally too troublesome to be effective (15). For largebare-root nurseries, only herbicides give dependable,long-term control, up to 30 days and longer betweenapplications. When herbicides are unavailable, diluteconcentrations of kerosene or other mineral spiritsalso control weeds fairly well in pine bare-root beds(Sec. 16.4.1). Before applying any herbicide, one mustascertain that its effectiveness is specific only for theplants treated and not toxic to seedlings (8, 16).

11.2.4 Shoot and Root Growth Control.-Under-cutting, lateral pruning, and top pruning are tech-niques to control root and shoot growth of bare-rootnursery stock. Root wrenching is practical only inlarge, mechanized bare-root nurseries. In very smallnurseries, none of these techniques may be used be-cause the scale of operation does not demand quality-control stock. Sections 16.4.6 and 16.4.7 contain moredetailed discussions of all shoot and root control oper-ations that are used in bare-root nurseries.

Undercutting is done with machetes and shovels insmall nurseries (14,171 and with tractor drawn ma-chines in large nurseries. Clean severing of taprootsstimulates lateral root growth but stops shoot growth.The technique is effective in manipulating shoot/rootratios.

Lateral root pruning severs roots between adjacentseedling rows. The technique allows easier lifting ofseedlings before packing and transporting. Machetesor machines are used, depending on nursery size.

Figure 11-4.-Pine plantations around (I nursery complex seroe as inoculum sources of mycorrhizal fungi, naturallyhy wind-home spores and artificially by man; the latter procedure must be used when hare-root bedsure fumigated. Note that urea directly behind work shed was cleared and prepared for new beds sothat old beds could be fullowed. Leaving three to four rows of trees would have retained windbreake/rtct of' thut urea fin existing beds.

55

Top-pruning (clipping) controls excessive shootgrowth. The technique is used selectively for individ-ual seedlings that are overtopping others and for en-tire beds when all seedlings have grown too fast andmust be kept longer before lifting. The operation stim-ulates root growth and is another method of manipu-lating shoot/root ratios. Hand shears are used in smallnurseries and tractor drawn mowers in large nurs-eries.

11.2.5 Liffing and Transporting. -The four proce-dures for taking bare-root seedlings to the field arelifting, protecting, grading, and transporting. Stockshould be lifted with shovels, never pulled directlyfrom the soil; the latter can strip root,lets fromseedlings, particularly if they are pulled from dry,clay soil. Soil is shaken off roots, which are immedi-ately washed, trimmed, and then stored in water,water slurries, or wet peat moss.

Grading separates plantable from cull seedlings.Grading standards vary by species and geographicalarea but usually include height, stem caliper, shoot/root ratios, foliage condition, and root mass. For somespecies, such as neem (Azadiruchtu indica), khaya(Khayu sp. 1, and mahoe, side leaves may be stripped tominimize water loss from tissues (19) (fig. 11-5). Onlylarger, well-developed seedlings should be planted;evidence shows that large seedlings outperform smallones, even up to 5 years after outplanting (2 1. If plantsare too large, pruning them back to a total length of18 to 30 cm may improve outplant survival (13).

Planting within a few hours of lifting, or at least thesame day as lifting, is the key to successful outplant-ing of bare-root stock (4,5 1. If transporting and plant-ing delays cannot be avoided, do not lift seedlings.Seedling roots must be kept cool, in the shade, andmoist at all times after lifting and while being trans-ported to planting sites (2 1. Section 16.5 gives otherlifting and transporting hints for large bare-root nurs-ery operations.

11.2.6 Stump Planting. -Some species such asCassia, Gmelina, and teak withstand trimming of themajor portions of the seedling stem and root system(9). The result is a stump, some 15 to 30 cm long (fig.11-5). Stumps are easily bundled, packaged, andshipped. Weight is minimal, and many more seedlingsare moved per day as compared to containerized andbare-root operations. Shade and protection instruc-tions for stumps are the same as those for bare-rootand containerized stock.

11.3 Other Later Tending Considerations

Several nursery operations already mentioned haveparticular influence on lifting and outplanting suc-cess. They are discussed separately to emphasize theirimportance.

11.3.1 Shoot/Root Ratios. -Determining shoot/root ratios is one way to assess overall seedling healthand suitability for outplanting. This is done by meas-uring oven dry weight or volume of seedling tops and

A. S T R I P P I N G

LEAVE TOP YOUNG GROWTHAND TERMINAL BUG

REMOVE OCQER GROWTH

8. STUMP PLANTING

ONE CAN REWOVE

ElUTlRE TOP FROMCASSIA, GMELINA, A N D , TECTONA

Figure 11-5.-Procedures fiw (A) stripping seedlings before transplanting to field or (3) makings~utnps fttr outplanting. Taken from (191.

5 6

dividing by oven dry weight or volume of seedlingroots. Shoot-to-root dry weight ratios of 2:l are accept-able for most seedlings. Higher ratios usually indicateexcessive shoot growth for corresponding root growth.

The ratio limit (2:l) must be used cautiously, how-ever, because ratios can be affected by shading andcontainer type (tables 11-l and 11-2). Actual pot vol-umes and shapes will limit root weights to certainmaximum values unless undesirable spiraling occurswithin pots.

Type of pot medium also affects root branching anddevelopment. Root branching is greater in mediumwith peat, perlite, and vermiculite than in soil-onlymedium due to the superior aeration properties ofsoil-less medium. In soil-only medium, greater devel-opment of tap roots and less lateral branching tend to

cause root curling or spiraling at the pot bottoms,especially when holding time in the nursery is toolong. Large spreading root systems are best because of1) their greater capacity for absorbing water and nu-trients from soil or pot medium and 2) greater surfacearea from which to extend new lateral roots after out-planting. Planting density also affects the root collardiameter growth of seedlings (6).

11.3.2 Hardening-Off. -Special seedling care andtreatment in the nursery allows production of green,healthy, and vigorous seedlings of sizes suitable foroutplanting. To grow large seedlings in short periods,water, fertilizer, and shade are used to stimulaterapid growth. However, “forced growth” regimes usu-ally produce succulent seedlings that do not surviveharsh conditions at planting sites. The hardening-off

Table 11-l.-The effect ofdifferent shade levels on the height growth, survival, root collar diameter,and shoot/root dry weight ratios of seedlings of P. caribaea var. hondurensis’

Measurement

Height (cm)Survival (a)Root collar

diameter (mm)Shoot/root

dry weight ratioMean dry weights (g):

0

14.195.3

2.31

2.17

Percent shade level

20 35

16.8 21.398.5 98.6

2.34 2.26

1.86 2.23

77

25.097.5

1.90

9.83

With LSD:ShootRoot

0.713 ” 0.190 0.706 t 0.148 0.726 LO.182 0.509 + 0.1320.367 2 0.132 0.446 t 0.164 0.379 -t 0.142 0.070 + 0.044

‘Each shade level represents the mean of 600 seedlings. The seedlings, 6 months old at the timeof measurement, were grown in Styroblock 8 cavities tilled with a peat-vermiculite mixture at theITF experimental nursery in Puerto Rico.

Table ll-2.-Znfluence of container type on root collar diameter, height, and shoot/root dry weightratios of seedlings of P. caribaea var. hondurensisr

Container typeVolume

o fcontainers

Root collar Shoot/rootdiameter dry weight ratio

Height

cc Mm Cm

Polyethylene bags 500 5.36 2.42 36.8Rootrainer 175 2.88 2.95 22.4Polypot 250 2.86 2.19 22.4Polypot 175 2.30 2.47 21.6Polypot 100 2.11 1.65 18.1Kraft tubepaper 305 3.13 5.04 25.2Kraft tubepaper 190 2.85 6.09 19.9Styroblock 8 120 2.11 2.59 25.1Styroblock 4 60 1.78 1.63 21.8

‘The containers were filled with a peat-vermiculite mixture; no fertilizer was added. Theseedlings were direct-seeded, 4 seeds per cavity, and culled to 1 seedling after 2 weeks. The datawere taken 6 months after sowing at the ITF experimentd nursery in Puerto Rico.

5 7

process increases probability that seedlings will sur-vive transplant shock. The process conditions bothcontainerized and bare-root grown seedlings to sur-vive without water and shade as long as possible inthe nursery before they are outplanted.

If seedlings have been under continuous shade, theshade should be removed, conditioning seedlings tofull sunlight. In the beginning, shade should be re-moved gradually for 2 hours during the day or for 1hour in the morning and 1 hour in the afternoon.After 3 or 4 days, length of the shade period is reducedanother 1 to 2 hours. By extending shade-free timegradually, seedlings will tolerate full sunlight with aminimum of shock within 2 to 3 weeks. Keeping 40- to50-percent shade throughout hardening-off, as is donein some countries (10 ), is not recommended.

Hardening-off also involves reducing the amount ofwater available to seedlings. One method is togradually extend the time between watering periodsby 2 or 3 days. The number of waterless days is pro-gressively extended until seedlings are capable of sur-viving up to 2 weeks or longer without water. Inhardening-off, wilting must be avoided. If it doesoccur, water is applied until wilting stops; then waterreduction begins again, but at less severe regimes.

When hardening-off seedlings in container beds,certain relationships between pot volume, pottingmedium, seedling size, and hardening-off must be con-sidered. If pot volume is small (less than 150 cc) andfilled with a peat: vermiculite medium, hardening-offseedlings for much more than 2 weeks is not possible.Older seedlings will transpire relatively largeamounts of water from small containers filled withporous medium. Thus, nursery managers should ob-serve and carefully record all information related towatering, wilting, and density in seedbeds. When in-formation is properly assessed, seedbeds can be ef&ciently managed with little loss due to improperhardening-off. With accurate information, nurserymanagers can also tell silviculturists and farmershow often seedlings should be watered if they must bestored for extended periods before outplanting.

11.3.3 Ccclling J-Root Plants. -Malformed tap-roots are common among hardwood seedlings grownin nurseries (fig. 10-l). When seedlings are improp-erly transplanted from germination trays to contain-ers, bent or J-roots occur (fig. 10-21. This is a seriousproblem because seedlings with J-roots fail to developproperly in the field, and older trees with J-roots aremore susceptible to windthrow.

The J-root can be avoided if young seedlings areused and they are carefully placed in transplant holes(Sec. 10.1.1.21. It is best to transplant seedlings beforelateral root branching occurs and before the seedlingflush develops.

To avoid bent roots in transplanting, seedlings arepulled through a transplant dish filled with water.

58

The roots trail and coalesce as seedlings are pulledthrough and lifted from the water. Seedlings are stuckinto the hole as deep as possible, pulled up tostraighten their roots, and then firmed up with a dib-ble stick (Sec. 10.1.1.2). If roots are X3 cm long, theyshould be trimmed back to about 5 cm in length.

LITERATURE CITED

1. Barres, H. Effects of root exposure on Honduraspine planting stock. Turrialba. 15(4): 348-349;1965.

2. Benson, A. D. Summary of nursery research 1967-1976. Forestry Commission of New South WalesResearch Note 37. Sydney, Australia: ForestryCommission; 1979. 18 p.

3. Briscoe, Charles B. Early results of mycorrhizalinoculation of pine in Puerto Rico. CaribbeanForester. 20(3-4): 73-77; 1959.

4. Briscoe, C. B. Lifting pine seedlings. Trop. For.Note 3. Rio Piedras, PR: U.S. Department ofAgriculture, Forest Service, Institute of TropicalForestry; 1960. 2 p.

5. Briscoe, C. B. Early lifting of pine seedlings. Trop.For. Note 10. Rio Piedras, PR: U.S. Departmentof Agriculture, Forest Service, Institute ofTropical Forestry; 1962. 2 p.

6. Burschel, Peter; MOB, Wolfgang; Soto, Manuel.Situation y manejo de 10s viveros chilenos depino insigne (Pinus rudiatu D. Don). Publica-ciones Cientificas. Valdivia, Chile: Facultad deIngenieria Forestal, Universidad Austral deChile; 1973. 26 p.

7. CONARE. (Compania National de Reforesta-cion). Algunas consideraciones de politica fore-stal relativas a las plantaciones forestales ybosques de produccion. Venezuela Forestal. 6:12-37; 1982.

8. Hadley, H. H.; Briscoe, C. B. Herbicides for forestplantations. Res. Note ITF-6. Rio Piedras, PR:U.S. Department of Agriculture, Forest Serv-ice, Institute of Tropical Forestry; 1966. 6 p.

9. Jackson, J. K. Nursery techniques in the savannaregion of Nigeria. Ministry of Agriculture andNatural Resources Res. Pap. 32. Ibadan, Fed-eral Republic of Nigeria: Federal Departmentof Forest Research; 1974. 8 p.

10. Khan, M. A. Waheed. Improved methods anddevices in nursery practice. Forestry Researchand Education Project Pamphlet 28. Soba-Khartoum, Republic of Sudan: Forest Depart-ment and United Nations Development Pro-gramme; 1966. 11 p.

11. Marais, L. J.; Kotze, J. M. Effect of mycorrhizaeon the growth of Pinus patulu Schlecht etCham. seedlings in South Africa. South AfricanForestry Journal. 107: 12-14; 1978.

12. Mar&, I.,. 3.; K&e, J. M. The effect of soil tem-perature on mycorrhizal developmen ndgrowth of seedlings of Pinus patula Schlecht etCham. South African Forestry Journal. 106:34-36; 1978.

13. Marrero, Jose. Study of grades of broadleaved ma-hogany planting stock. Caribbean Forester.3(2): 79-88; 1942.

14. Marrero, Jose. Efecto de la poda radicular de dosespecies forestales. Caribbean Forester. 8(3):241-244; 1947.

15. Marrero, Jose. Effect of plastic mulch on weedgrowth and early height of Honduras pine. Res.Note ITF-4. Rio Piedras, PR: U.S. Departmentof Agriculture, Forest Service, Institute ofTropical Forestry; 1965. 5 p.

16. Munoz, J. E.; Hill, L. W. The use of herbicides forsite preparation and their effects on tree sur-vival. Res. Note ITF-12. Rio Piedras, PR: U.S.Department of Agriculture, Forest Service, In-stitute of Tropical Forestry; 1967. 6 p.

18. Nobles, R. W.; Briscoe, C. B. Root pruning of ma-hogany nursery stock. Res. Note ITF-7. RioPiedras, PR: US. Department of Agriculture,Forest Service, Institute of Tropical Forestry;1966. 4 p.

18. Vozzo, J. A.; Hacskaylo, Edward. Inoculation ofPinus caribaea with ectomycorrhizal fungi inPuerto Rico. Forest Science. 17(2): 239-245;1971.

19. Weber, Fred R. Reforestation in arid lands. PeaceCorps/VITA Publications Manual Series 37E.Washington, DC: Government Printing Office;1977. 248 p.

20. Weidelt, H. J., camp. Manual of reforestation anderosion control for the Philippines. Eachborn,Germany: Agency for Technical Cooperation,Ltd. (GTZ); 1975. 569 p.

CHAPTER 12

12. PROTECTION AND PEST CONTROL

Nursery stock requires a large investment of time,labor, and monetary resources. Without protectingthis investment, large seedling lasses may occur (3,21 ). Such losses can be catastrophic when communi-ties need seedlings to produce firewood or protect crit-ical watersheds. Large and small nurseries need pro-tection from several physical and environmentalelements, as well as from insects and diseases.

12.1 Property and Seedling Security

Daily guard service to protect seedlings and prop-erty is very costly. However, it may be the only alter-native in areas where animal and human populationsare very high, and where small tools can be easilystolen and seedlings destroyed. In poor communities,payment to workers in food rather than direct cashmay be best.

Adequate fences deter animals and people. Fencesbuilt of treated wood and with proper materials last along time. In some projects, replacement posts can beharvested from field plantings. When diesel oil andpentachlorephenol are available, hot-cold treating ofposts in barrels or drums is relatively inexpensive.Live fences and hedges with thorny plants or localshrubs may be adequate. Diagrams are available onhow to construct. self-closing gates and other fencingstructures (22 ).

Windbreaks reduce dry winds that evaporate mois-ture from seedbeds (16). Local tree species are pre-ferred, but prolific seeders such as Leucaena areavoided. Wind blown seed from windbreaks germi-nate and compete with seedling root systems growingin seedbeds and germinating trays. Removing theseinvaders is costly, and root systems of seedlings aredisturbed in weeding.

Where fires are frequent, a 2- to 3-m firebreakshould be maintained around the entire nursery (22 1.Water outlets should be located at several places nearthe perimeter so that water is readily available if afire jumps the firebreak.

12.2 Pests and Diseases

Diversity of climate and environments in the trop-ics precludes simple prescriptions for insect and dis-ease problems of forest nurseries. This chapter istherefore a brief review of some potential problemsand is not all-inclusive. A summary of major pests,species attacked, symptoms, and recommended treat-ments is given in table 12-1.

12.2.2 Symptoms. -When seeds (5) or vegetativematerials are collected or imported from outside acountry, they should be checked immediately uponarrival at the nursery for symptoms of disease or in-sects. Unfortunately, phytosanitary certificates donot always guarantee that undesirable insects or dis-eases are absent in imported seeds or plants.

Some insects are apparent from chewed leaves; oth-ers are seen on the underside of leaves. Webs and eggsare other signs of infestation. Some common pests arethose in figure 12-1.

Disease symptoms can include sooty appearing ma-terials, a form of fungus; rust spots; irregular-shapedblotches or mosaics of different colors; and sticky dis-charges. Discoloration symptoms can be caused byeither disease organisms or by mineral deficiencies(Sec. 13.2).

59

Table 12-l.-Srrnlrvary of major nursery pests and diseases, forest species attacked, and controltreatments recommended

Pest type Seedling species affected Control

A. Chewing mouth parts:CutwormsCricketsLeaf minersShoot borers

Sugarcane root/stalkborers

Mahogany, teak, pinesTeakMahoganyMahogany, Spanish-cedar, and

other Meliaceae family speciesMahogany

B. Piercing/sucking mouthparts :

AphidsMealybugsThripsScales/mites

Teak, kadam, GmelinaTeakKadamPines

C. Large pests:SpidersBirds

PinesPines/hardwoods

Rats/mice Pines/hardwoods

Diseases

A. Damping-off fungi

B. Seedling needle blightC. Brown needle disease

D. Root rot fungi

Pines/hardwoods

PinesPines

Pines/hardwoods

Ingested poisons:Spectracide, chlordaneGeneral insecticideGeneral insecticideSyst.emic insecticides

Soil drench insecticides

Contact poisons:

VariousVariousVariousVarious

Various controls:Ingested/contact poisonsChemicaf repellents

added to seedsChemical repellents;

cover seeds; pet cat innursery

Pot media and soi steril-ization; soil drench fun-gicides

Various fungicidesBordeaux mixture (i.e.,

copper sulfate)Soil sterilization; good

watering control andmonitoring

12.2.2 Control. --When insects or diseases occur,control measures are needed quickly. Appropriatechemicals are applied (10) and are used according tolabeling instructions, with respirator (mask) and ade-quate clothing to reduce risk of toxicity to humansduring application. The kind of control used dependson which pesticides are locally available and the kindof pest. Sometimes, removing affected seedlings is suf-ficient.

Insects are divided into two major groups: thosethat chew leaves and those that suck juices out ofplants. The controls for each are quite different. Forinsects with piercing-sucking mouth parts, a directcontact poison is required, i.e., one that covers andkills them. For those insects with chewing mouthparts, toxic substances deposited on leaves are in-gested and eventually cause death.

60

12.3 Common Chewing Pests

12.3.1 Pine Seedling Cutworm. -Cutworms arenoticed when they are about 2 mm long, shortly afteremerging from eggs. Larvae feed for 1 or 2 days, chew-ing on tender needles near the seed cap. Followingemergence, they are light yellow in color with a thinbrown stripe down the back. As the larvae feed, in-gested chlorophyll is absorbed, and they develop adeep green color.

Cutworm larvae eat cotyledons at their point of at-tachment on the stem; the cotyledons are completelysevered, and the seedcoats fall to the ground. Oncecotyledons are severed, larvae crawl downward, cutthe hypocotyl, and then proceed to other seedlings.After they grow to about 25 mm long and turn lightbrown, cutworms are easily observed crawling amongseedlings. Before burrowing into germination

larva

M O T H

nymphs

A P H I D

SAWFLY

armored soft

crawlers

protectivecover ing SCAI E S

body

larvae

D E E TLE WEEVIL

spider

er iophyid

nymphs

z Figure 12-l.-Common nursery insects. (Drawing from A. Krochmal, USDA Forest Service, retired, Asheville, NC).

medium for metamorphosis, each cutworm can de-stroy 20 to 30 seedlings.

Cutworm attack occurs year-round and has beenobserved on both P. caribaea and P. oocarpa seedlings(13 1. Cutworms have also killed teak and mahoganyseedlings in East Africa. Effective controls were chlor-dane at 0.45 kg active ingredient (A. I.) per 378 litersof water or Zectran at 0.23 kg per ,378 liters of water.An insecticide such as Spectracide can also controlcutworms.

Zz.Y.2 Crickets and Termites. -Other commonstem chewers in East Africa are crickets and termites.Major activity was limited to teak seedlings. Severalinsecticides controlled these pests (13, 15).

12.3.3 Leaf Miners. -Mahogany seedlings are alsoattacked by leaf miners that lay eggs on the backsideof the leaf. Leaf miner larvae cause seedling leaves tocurl. Although leaves die, seedlings ordinarily sur-vive; thus, leaf miner attacks are not a serious prob-lem.

12.3.4 Shoot and Root Borers. -Perhaps the mostserious insect attack in tropical nurseries is that ofshoot borers on mahogany and Spanish-cedarseedlings. Although seedlings are seldom killed, theeconomic damage is high. A major difficulty is train-ing workers to detect shoot borers or their eggs on theundersides of seedling leaves.

The most serious shoot borer is Hypsipylagrandella, which attacks through the terminal shoot(fig. 12-2). If outplanted (carrier) seedlings serve asbreeding habitat in new plantings, virtually all termi-

nal shoots are attacked within a year (17). The resultis multiple-branched stems that reduce the commer-cial worth of mature trees. A systemic insecticide canbe applied in planting holes when seedlings are out-planted; however, this control is costly and not tooeffective (6, 18).

A second borer, Diaprepes abbreviatus (the sugar-cane stalk borer) attacks both lateral roots and tap-roots of mahogany seedlings and will work its way upthe stem (fig. 12-3). Heavy infestations can kill entireseedling beds (I 1. Soil drench insecticides will controlthis pest. In its adult form, the borer is a leafeater thatcauses heavy defoliation.

12.4 Common Sucking Pests

12.4.1 Aphids. -Aphids secrete honeydew thatserves as a growth medium for sooty mold, givingplants a dark (sooty) appearance. Aphids attack teak;scaly aphids have attacked kadam and Gmelinaseedlings in Puerto Rico, but damage was not serious.

12.4.2 Mea&bugs. -Mealybugs, related to aphids,eat holes in leaves. They are not very visible untilreproduction begins and their numbers increase.Mealybugs seldom kill seedlings, but damage can beserious if seedlings lose large amounts of photosyn-thetic tissue.

12.4.3 Thrips. -Kadam seedlings and trees cansustain heavy leaf damage by thrips (Selenodthripsrubrocinctus g&d). If attack is widespread in thenursery, infected seedlings easily carry thrips to thefield, resulting in the eventual death of some trees.

Figure 12-3.-Damage to mahogany seedling roots from sugarcane stalk/rootborer (Diaprepes abbreviatus) in Puerto Rico nursery.

12.4.4 Scales and Mites. -Scales range in colorfrom green to brown, and their bodies are coveredwith wax. Like aphids, scales are not very visible un-til reproduction allows numbers to increase substan-tially (23 ). Mite damage occurs as small spots, usuallyon the undersurfaces of leaves. Mites have eight legsrather than six as do true insects. Spider mite attacksare known for pine seedlings and older trees in Ja-maica and naturally regenerated seedlings in PuertoRico (I). As long as seedlings are otherwise healthy,spots and yellowish foliage symptoms will graduallydisappear.

12.5 Larger Pests

12.S.l Spiders. -Spider damage was observed in1974 on P. caribaea seedlings planted on Vieques, asmall island southeast of Puerto Rico (ITF, unpub-lished data). The unidentified spiders spun websaround the terminal and side shoots of the seedlingsand laid eggs inside the nests. Death of some shootsoccurred; it was not determined whether death wascaused by physical (strangling) or chemical means.An insecticide such as Spectracide can be sprayed tokill spiders that are damaging seedlings.

12J.2 Birds. -Special efforts are needed to protectnewly germinated seedlings from birds (2). They eatseeds that are partly exposed in germination trays orthat are easily scratched from seedbeds. They disturbpot medium while looking for insect larvae and cut-worms (14 ). Birds also eat exposed seeds before cotyle-dons emerge. If this happens, seedlings generally diebecause the apical meristem is also eaten along withthe seedcoat. A flock of birds can easily eat severalthousand seeds per day.

Although repellents (with stickers1 are available tocontrol feeding on seeds by birds, the best method is tocompletely enclose germination trays and seedbedswith a box frame covered with Saran until all seedshave germinated and seedcoats are thrown (fig. 5-2).Such control is impractical for large, direct-seeded

seedbeds where repellents must be placed on seedsbefore they are sown. Large shade houses are the mosteffective way to keep birds away.

Where bird populations are low, straw or othermulches are used to protect seeded bare-root beds.However, large numbers of birds may feed heavily onmulched seedbeds. For some hardwood species likemahogany, seeds are not too palatable to birds or areso small (kadam and eucalyptus) that birds do not eatthem. Birds do not eat seeds of species such as teakbecause the seedcoat is too hard or the seed is toolarge.

12.53 Rats andMice. -Rats and mice can be seri-ous problems if direct-seeding is used. Basically, thesame procedure mentioned above for birds is also usedto protect seeds from rodents. Because Saran shadescreens are easily chewed through, they are rein-forced with small mesh (6 mm) metal screening at thesides. Seed repellents are also effective controlsagainst rats and mice. Appendix 12 (table A12-31 liststhe repellents currently available.

Repellents must be used in conjunction with asticker. The function of the sticker is to hold the repel-lent on the seedcoat during germination. Neithersticker nor repellent must interfere with germina-tion.

126 Diseases

12.6.1 Damping-Off. -Damping-off is commonthroughout most areas of the world and kills seedlingsof all species (151. In forest nurseries, it is usuallymost severe among conifer seedlings. Two types mayoccur: 11 preemergence damping-off where pathogenicfungi attack and destroy seeds before hypocotyl emer-gence or attack seedlings before they have emergedfrom the soil and 2) postemergence damping-off wherefungi attack seedlings shortly after they haveemerged from the soil or germination medium. Post-emergence fungi attack seedlings at or slightly abovethe root collar, causing seedlings to wilt and fall. At-

63

tack can be rapid, with entire seedbeds being affectedwithin 24 hours. Postemergence damping-off is iden-tified by a small dark-colored ring-like growth aroundthe lower stem.

Cytological studies have shown that the pathogenicfungi quickly spread throughout stem and root tissue.Thus, once the attack has begun, affected seedlingscannotbesaved(7,8,11,12,19,20).

Effective controls are: sterilizing seedbeds; avoid-ing excess moisture, temperature, and humidity ingermination trays; avoiding excess nutrients such asphosphorus and nitrogen in seedbeds; and maintain-ing acidity of germination medium at a low level,around pH 5.0. Spores of most pathogenic fungi sur-vive for many years in soil. Steam and methyl bro-mide sterilization are the best treatments for soil orgermination medium. An alternate method is drench-ing with a formalin (2 percent solution in water) mix-ture. About 2 weeks before sowing, beds are saturatedwith about 4 liters of the formalin solution per squaremeter of bed and then covered with a darkpolyethylene sheet. After 1 week the polyethlenesheet is removed and the bed material is turned orplowed. After 1 day of aeration, beds can be sown withseeds or transplants can be lined-out.

Once damping-off has occurred in a seedbed, germi-nation medium should be removed if it cannot be ster-ilized in place. Fresh, sterilized germination mediumshould be used. Table 12-1 lists other effective diseasecontrol treatments.

12.6.2 Seedling Needle Blight. -This disease issometimes found on pine seedlings; it is usually moreprevalent at a late growth stage, such as in planta-tions (9). In Malaysia, weekly spraying with Daconil2787 and Phelam gave the best control over needleblight caused by Colletotrichum floeosporioldes in thenursery. Phelam, however, should not be used be-cause it is reportedly toxic to mammals. Captan, fer-barn, Polyram Combi, Cobosx, and Dieldrex 15 pro-vided less protection than Daconil 2787.Cylindrocladium macrosporum and C. pteridis havealso attacked P. caribaea and P. oocarpa in Malaysia.

12.6.3 Brown Needle Disease.-This disease hasoccurred in Puerto Rico and in Malaysia on P. carib-aea. The causative agent is Cercospora pini-densi-flora. In India, C. pini-densiflora was controlled by a2-week spraying with a copper sulfate (bordeaux solu-tion) based fungicide. Disease symptoms appear simi-lar to those of needle blight, although the infectionagents are different. Needle blight disease does notalways lead to .death, but once a seedling is infectedwith this disease, death invariably occurs.

12.6.4 Purple Folia.ge. -Pine seedlings often de-velop purple foliage while in the nursery. Though nodisease organism has been identified, mild attack bya disease cannot be entirely ruled out. Althoughsevere phosphorus deficiency is indicated by purple

64

needles, phosphorus deficiency is not expected in wellfertilized seedbeds. Trace element imbalances mayalso be responsible for the purple foliage. No treat-ment except monitoring the fertility level of seedbedsor pot medium is recommended, since the purple colordisappears once seedlings are outplanted.

12.6.5 Root Rot.-Seedlings often turn yellow-brown, with the succulent terminal flush falling over.Because affected seedlings appear to be under waterstress and look wilted, the usual reaction is to waterthem. Closer inspection may show that the problem isnot a lack of water, but rather excess water that hascaused root rot. The only proof is to lift some wiltedseedlings and inspect their roots. If the taproot is ne-crotic and lateral roots are absent, then some form ofroot rot probably exists (4). Sometimes the cortex atthe root collar is so rotten that it is stripped off asseedlings are lifted from the soil.

The most effective control of root rot is to avoidoverwatering. However, if root rot does occur, theproblem is probably compounded by poorly drainedand poorly aerated pot medium or seedbeds. Pottingmixtures can be changed to provide better aeration(Chap. 9).

LITERATURE CITED

1. Barry, Patrick; Anderson, Bob. Evaluation of in-sects and disease pests of trees in Puerto Rico.For. Pest Manage. Rep. 81-1-29. Asheville, NC:U.S. Department of Agriculture, Forest Serv-ice, Southeastern Area, State and PrivateForestry; 1981. 33 p.

2. Burschel, Peter; Mall, Wolfgang; Soto, Manuel.Situation y manejo de 10s viveros chilenos depino insigne (Pinus radiata D. Don). Publica-ciones Cientificas. Valdivia, Chile: Facultad deIngenieria Forestal, Univesidad Austral deChile; 1973. 26 p.

3. Cordell, Charles E.; Filer, T. H., Jr. Integratedpest management. In: Lantz, Clark W., ed. andcamp. Southern pine nursery handbook. At-lanta, GA: U.S. Department of Agriculture,Forest Service, Southern Region; 1984: 13-1 to13-17. ’

4. Donald, D. G. M. The use of slow-acting fertilizersin the production of Pinus radiata nurseryplants. Communication 59. Mededeling, SouthAfrica: Faculty of Forestry, University of Stel-lenbosch; 1973. 12 p.

5. Fernandez Magan, F. J. Anotaciones sobre el cul-tivo de1 Eucalyptus glob&us en 10s viveros de1litoral Gallego. Instituto Forestal de Investiga-ciones y Experiencias Comunicacion 103.Madrid, Espana: Centro Forestal Regional deLourizan; 1971. 30 p.

6. Gara, R. I; Allan, G. G.; Wilkings, R. M.; Whit-more, J. L. Flight and host selection behavior ofthe mahogany shoot borer, Hypsipyla grandellaZeller. Zeitschrift fuer angewandte Entomolo-gie. 72(3): 259-266; 1973.

7. Gibson, I. A. S. Damping-off in forest nurseries.Mycological Note 35. Nairobi, Kenya: EastAfrican Agriculture and Forestry Research Or-ganization; 1954. 3 p.

8. Gibson, I. A. S. Nursery disease survey-1967.Mycological Note 50. Nairobi, Kenya: EastAfrican Agriculture and Forestry Research Or-ganization; 1968. 3 p.

9. Gibson, I. A. S.; Munga, F. M. Terminal crookdisease of seedling pines in Kenya. MycologicalNote 34. Nairobi, Kenya: East African Agricul-ture and Forestry Research Organization;1966. 2 p.

10. Hamel, Dennis R. Forest management chemi-cals-a guide to use when considering pesti-cides for forest management. Agric. Handb.585. Washington, DC: U.S. Department ofAgriculture, Forest Service; 1983. 645 p.

11. Hocking, D. Damping-off in pine nurseries: 4.Fungi associated with diseased and healthyseedlings and with seed. Mycological Note 42.Nairobi, Kenya: East African Agriculture andForestry Research Organization; 1966. 7 p.

12. Hocking, D. Damping-off in East African pinenurseries: 9. Practical considerations on con-trol. Mycological Note 48. Nairobi, Kenya: EastAfrican Agriculture and Forestry Research Or-ganization; 1966. 3 p.

13. Hocking, D.; Jaffer, A. A. Field observations onroot-rot of teak and nursery disorders. Mycolog-ical Note 41. Nairobi, Kenya: East AfricanAgriculture and Forestry Research Organiza-tion; 1966. 6 p.

14. Holmes, D. A.; Floyd, A. G. Nursery techniquesfor raising eucalypts in jiffy pots on the NewSouth Wales North Coast. Res. Note 22. NewSouth Wales, Sydney: Department of Conserva-tion, Forestry Commission; 1969. 15 p.

15. Jackson, J. K. Nursery techniques in the savannaregion of Nigeria. Research Paper 32. Ibadan,Federal Republic of Nigeria: Federal Depart-ment of Forest Research, Ministry of Agricul-ture and Natural Resources; 1974. 8 p.

16. Kittredge, Joseph. Forest Influences: the effectsof woody vegetation on climate, water, and soil,with applications to the conservation of waterand the control of floods and erosion. New York:Dover; 1973. 394 p,

17. Lamb, F. Bruce. Mahogany of tropical America.Ann Arbor, MI: University of Michigan Press;1966. 220 p.

18. Mosquera Moreno, M.; Whitmore, J. L. Bibli-

ografia sobre Hypsipyla. In: Studies on theshootborer Hypsipyla grandella (Zeller) Lep.,Pyralidae. CATIE Misc. Publ. 101. Turrialba,Costa Rica. 130-138; 1976. Vol. II.

19. Setliff, Edson C.; Hocking, D. Damping-off in pinenurseries: 2. Methyl cellulose application ofseed dressings at Kisarawe. Mycological Note33. Nairobi, Kenya: East African Agricultureand Forestry Research Organization; 1966.7 p.

20. Setliff, Edson C.; Hocking, D. Damping-off in pinenurseries: 3. Partial control by soil fumigationwith vapam. Mycological Note 46. Nairobi,Kenya: East African Agriculture and ForestryResearch Organization; 1966. 3 p.

21. Sutherland, J. R. Pest management in Northwestbareroot nurseries. In: Duryea, Mary L.; Lan-dis, Thomas D., eds. Forest nursery manual:production of bareroot seedlings. The Hague,The Netherlands: Martinus Nijhoff/Dr W. JunkPub.; Corvallis, OR Forest Research Labora-tory, Oregon State University; 1984: 210-283.

22. Weber, Fred R. Reforestation in arid laiids. PeaceCorps/VITA Publications Manual Series 37E.Washington, DC; 1977. 248 p.

23. Whitmore, J. L.; Medina-Gaud, S. White peach-scale attack on toon in Puerto Rico. Journal ofAgriculture of the University of Puerto Rico.58(2): 276-278; 1974.

CHAPTER 13

13. NURSERY NUTRITION

Growth and performance of nursery stock is relatedto the nutrition of seedbed soil or container medium inwhich seedlings grow as well as the genetics and vigorof seeds sown. The fertility of nursery soil is predictedby both chemical and biological methods. If nutrientdeficiencies exist, they can be corrected with organicor inorganic fertilizers that are short- or long-termacting. This chapter discusses nursery nutrition andseveral fertilizer alternatives. Appendix 13 givespractical guides for using and applying fertilizers.

13.1 Essential Elements

There is disagreement on which elements are trulyessential for plant growth (20 ). Generally, carbon, hy-drogen, and oxygen comprise the bulk of seedlingweight. They are obtained directly from carbon diox-

65

ide tC0,) and water (HsO), which are not usually lim-iting except in waterlogged or very dry environments.Elements are traditionally called macroelements ormicroelements, depending on whether plants usegreater or lesser quantities. Roots take up mineralsprincipally from the solution or exchange complex ofnursery soil or the container medium. Known func-tions of each element are summarized in table 13-1.

Each tree species, its varieties, and even individu-als of a species have distinct nutrient requirementsand uptake rates. Thus, table 13-1 is only a guide tothe “basics” of plant nutrition. Elemental concentra-tions can vary by plant component (leaves, twigs,branches, fruits, and roots), age, position within theseedlings (top, center, or lower stem area), season(spring or fall), and climate (dry or wet) (51. General-izations about seedling nutrition are therefore some-times difficult to make.

13.2 Nutrient Deficiency Symptoms

Visual symptoms are usually the first signs thatseedlings are growing abnormally (20). Common

Table 13-l.-Function of major and minor elements in nursery nu-trition’

Element Role in seedling nutrition

N (nitrogen )

P (phosphorus)

K (potassium)

Ca (calcium)

Mg (magnesium)

S (sulfur)

Fe (iron)

Mn (manganese)

Cu (copper)

Zn (zinc)13 f boron I

M O (molybdenum~

Macronutrients

Essential part of chlorophyll and proteins;fosters vegetative growth.

Promotes root growth and stem strength;important in all energy transfers withinplants.

Promotes starch and sugar formation, rootgrowth, resistance, shoot strength, andplant vigor.

Enhances N uptake, cell elongation, anddevelopment of meristematic tissues.

Major constituent of chlorophyll in plants;important in P metabolism and enzymeactivation.

Essential for synthesis of S-containingamino acids and nitrogen fixation byl e g u m e s .

MicronutrientsImportant in chlorophyll production and

enzyme activation.Activates enzymes regulating carbohy-

drate metabolism and essential for pho-tochemical (Hill) reaction.

Metal activator for several enzymes andpossibly light reaction in plants.

Metal activator of enzymes.Responsible for several regulator mecha-

nisms in many plants, including sugartranslocation across cell membranes andoxidation processes.

Required for N-fixation in legumes and ni-trate reduction in nonlegumes.

‘Sources: I.9 ), (20 ).

6 6

symptoms are: severe stunting, delayed or abnormalgrowth (twisted or missing needles), leaf discoloration(bright yellow, purple, or red instead of green), andabnormal root growth. Symptoms develop when inter-nal plant growth processes are interrupted by lack ofone or more elements and by the organic metabolitesthat subsequently accumulate.

Published color pictures show deficiency symptomsfor several temperate (19) but few tropical (22) spe-cies. Lack of one element can cause divergent symp-toms in different species. Also, similar symptoms maybe caused by deficiencies of different elements (e.g.,general chlorosis by lack of either N or S).

Some symptoms are caused by multiple nutrientdeficiencies; others are not nutrient related at all. Forexample, if seedlings turn yellow, root systems arechecked first to see whether overwatering has reducedaeration, thus killing roots and blocking nutrient andwater uptake. When deficiency symptoms appear, ir-reparable damage has probably occurred in shoot orroot tissue. Though we recognize the limitations oftrouble shooting nutrient deficiencies, a generalized“key” to visual symptoms is given in table 13-2.

13.3 Foliage (Tissue) Sampling

Foliage, tissue, or plant analysis is used opera-tionally to determine seedling nutritional status be-fore deficiency symptoms appear (12, 14, 24). Therationale for this method is: if adequate elementalconcentrations exist for good growth in plant foliage,then concentrations of the same element are adequatein the soil. Through nursery and field fertilizer cali-bration trials, one determines “critical” concentra-tions, i.e., elemental levels at which plant growthdrops below optimum. Excess amounts of certain ele-ments such as Fe, B, or Mn are toxic to plants. Usu-ally, however, plants absorb excess nutrients withoutharmful effects. Good plant growth with nutrient lev-els beyond those normally needed is called “luxuryconsumption” (5 1.

In temperate areas, foliage is sampled at first hard-ening, usually in late summer when nutrient concen-trations are less variable than at other times in thegrowing season. Except for a few instances, monthlyand seasonal fluctuations are not known for tropicaltree species that grow all year long (table 13-3). How-ever, sampling can be done one-third and two-thirdsthrough the period that seedlings are held in the nurs-ery before outplanting (e.g., for seedlings held 24weeks, then sample at l/3 of 24 = 8 and 213 of 24 = 16weeks).

Best results are normally obtained by sampling ma-ture, fully developed leaves or fully elongated needles.If seedlings lack secondary needles, dry and grind allof the above ground tissues of several seedlings. Ifsecondary needles are present, dry and grind theneedles only, after collecting fascicles from a com-

.

Table 1!3-2.-Key to the classical symptoms of various nutrient deficiencies’

Symptoms Symptoms may be related to

a. The dominant symptom is chlorotic foliage (dis-coloration).b . Entire leaf blades are chlorotic.

c . Only the lower leaves are chlorotic, fol-lowed by necrosis (tissue death) and leafdrop.

cc. Leaves on all parts of plant are affectedand often have a beige cast.

bb. Yellowing of leaves takes the form of inter-veinal chlorosis.

c . Only older leaves exhibit interveinalchlorosis.

cc. Only younger leaves exhibit interveinalchlorosis.d . This is the only symptom.dd. While younger leaves have inter-

veinal chlorosis, the tips and lobes ofleaves remain green, followed byveinal chlorosis and rapid, extensivenecrosis of leaf blade

ddd. Young leaves are very small, some-times missing leaf blades altogether,and internodes are short, giving arosette appearance.

aa. Leaf chlorosis is not the dominant symptom.b . Symptoms appear at base of plant.

c . At first, leaves are dark green andsmaller than normal. Later, purple piement develops in older leaves.

cc. Margins of older leaves burn or small ne-crotic spots appear on older leaf blades.

bb. Symptoms appear at top of plant.c . Terminal buds die, giving rise to a

witches’-broom.cc. Margins of young leaves fail to form,

sometimes yielding trap-leaves. Growingpoint ceases to develop, leaving a bluntend.

Nitrogen

Sulfur

Magnesium

Iron and/or manganese

Copper

Zinc

Phosphorus

Potassium

Boron

Calcium

‘Adapted from material of P. Nelson, Horticulture Department, North Carolina State Uni-versity, Raleigh.

posite sample of many seedlings. Collections are bestmade in the early morning, before seedlings beginsynthesizing carbohydrates and utilizing nitrates ac-cumulated at night.

Leaf petioles from large-leaved seedlings (e.g., fromteak or mahoe) should not be included in the sample.Total analysis is performed on tissue samples, usingstandard procedures (6, 7).

Rapid or “quick tissue tests” on plant sap are some-times used (201. Results, however, are not quantita-tive and should not be substituted for diagnosticanalyses. Sampling done in duplicate provides extramaterial for checking test results.

Foliage analysis interpretations must consider bothenvironment of the seedlings tested and their physio-logical state. Are seedlings growing vigorously or arethey stunted? Are there signs of above ground or be-low ground insect or disease attack? Is seedbed

medium well aerated or is soil moisture excessive?Have climatic conditions before sampling been un-usually moist or dry? Is soil pH value or salt contenttoo high? For example, discolored and stuntedseedlings with “high” tissue values for N, P, and Kdoes not mean that these nutrients are present inadequate amounts. Poor growth, but seemingly ade-quate tissue nutrient levels, suggest that some otherfactor is limiting seedling growth, perhaps under-ground root borers (fig. 12-3).

Foliage analysis has two disadvantages. Calibra-tion trials to establish high, low, medium, and criticallevels for each element are costly and time consum-ing. Also, techniques and equipment needed for chem-ical analyses are rather sophisticated, requiringhighly trained personnel. If facilities for agriculturalfoliage research exist, techniques are easily adaptedfor forest nursery diagnostic work.

67

Table 13-3.--Mc~r~ fiJiage cormr~trations far forest tree for comparison

Foliageelement

concentrations

Pinas caribaea var. hondurensisl

3 yr 4 yr

Normal Foxtail Normal Foxtail

Eucalyptusdeglupta2

(15 mo)

Pinuselliotti Conifers4 Hardwoods4

N. 'i 0.98

P. ‘i 0.08

K. ‘i 0.77

Ca. 5 0.27

Mg, % 0.08

Na, %

Mn, p/m

Cu, p/m

Zn, p/m

Fe, p/m

B, p/m

Al, p/m

0.14

491

5.1

3 0

110

12

493

1.25 0.92

0.12 0.09

1.09 0.90

0.26 0 .25

0.10 0 .10

0.17 0.11

572 4 7 9

5.9 4.8

37 29

116 50

15 12

469 4 1 0

0.18 . . . . . . . .

724 8-2’70

4.7 2.0-6.4

3 8 6-49

5 9 32-148

12 15-84

557 . . . . . . . .

Sources: ‘( 10 ), “( 7 ), ? I1 ), 4(8 ); data for p/m apply to both conifers and hardwoods.

1.16 0.64-2.04 0.98-2.16

0.10 0.10-0.69 0.12-0.43

1.09 0.44-1.78 0.23-1.73

0.34 0.46-1.40 0.08-0.79

0.13 0.13-0.42 0.08-0.26

.........

.........

.........

.........

.........

.........

1.00-1.10(deficient)

1.00-4.00(medium)

0.10-0.30(medium)

0.30-0.50(medium)

0.35(deficient)

0.50-1.60(medium)

0.12-0.70(medium)

0.30-2.30(medium)

. . . . . . . . . . . . . 0.08-0.40(medium)

-------- 100~5,000 (medium) -------

_____-____ 4-12 (medium) _____.._.__

____________-____ lo-125 ___________._____

------------- * ---- 30.40 ---------________

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13.4 Soil Tests

Soil tests directly determine the nutrient-supplyingpower of a soil. Methods require a knowledge of chem-istry and laboratory instrumentation, usually foundat a country’s agricultural research station. Soil testsare usually better than foliage tests because they in-dicate a nursery soil’s nutritional status and fertilizerneeds before seeds are sown or seedlings are trans-planted (23 ).

Other objectives of soil tests are:l to maintain the fertility status of different nursery

beds andl to predict the response of beds to lime and fertilizer

additions.The nutrients of greatest interest are the amounts

of cations (Ca, Mg, and K) and P. Organic mattercontent, pH value, and salt levels are also important.

The most critical part of soil testing is obtaining arepresentative sample. All areas that. vary in appear-ance, slope, drainage, soil type, or past treatmentsshould be sampled separately. In areas where fertiliz-ers were previously applied in bands, samples shouldbe taken between the bands. A single 0.5 to l.O-kgsample consists of a composite of 10 to 20 tube cores or

spade scrapings (fig. 13-Q usually taken to about 15cm (normal seedling root depth). All sampling shouldbe done well ahead of scheduled sowing so that fertil-izer can be applied if needed.

Many different extracting solutions are used to de-termine soil nutrient concentrations or contents (I J.For permanent nurseries, the same extraction proce-dures must be used from year-to-year to standardizeinterpretations. Where no prior data exist for newnurseries, soil test data should be taken and analyzedin a manner similar to that used for local or regionalagricultural research. Data from crop trials are thenused to determine interim fertility levels for nurserysoils. Fertility tests should be run on homemademixes to assure that all essential elements arepresent in adequate quantities. Examples of soil fer-tility standards for field nurseries are given in table13-4.

13.5 Special Soil Problems: Acidity and Salts

Soil reaction or pH value is a measure of the degreeof acidity or alkalinity of a soil. A scale of 0 to 14 isused, with 7.0 as the neutral point (fig. 13-2~ Soils

ll

ll

0

ll

lC

lOPEN

l WORK STORAGEl

lAREA

8 LABl AREA

ll

7l l

POTTINGe l SHED

D 0

ONE BAG HOLDS12 TUBE CORESOR SHOVELSCRAPINGS

0 l.0C41loW Of SOIL CORES OR SHOVEL SCR4PlRQS TO OEPTH OF IS cm.

A B4RE ROOT PINE 4RE4; WELL ORIINED SOIL --Dl460N4L S4YPLING

B b4Rt ROOT PINE 4REA; YORE POORLY DRAINED SOIL -- R4NDOY SAMPLING

c 04RE ROOT MAROWOOO 4REA; WELL-DR4INED SOIL-- Dl4ODNAL SAYPLINO

Figure 13-l.-Collecting nursery soil samples for chemical and physical analyses. Take 10 to 20tube cores or shovel scrapings for each distinct soil type, drainage area, andlor bedarea devoted to different species. All soil samples are usually taken to a depth of 15om. They are bulked (mixed) into one composite sample that is eventually analyzedin a soil laboratory. In the example above, at least three samples are taken, one eachfrom areas A, B, and C. Zf size of an area is 1 ha or greater, divide it into smallerdivisions, with a composite sample taken from each division. For uniform areas,criss-cross sampling (areas A and C) is easiest, whereas random or zig-zag sampling(area B) is best for areas with high soil variability.

Table 13-d.-General field soil fertility standards used for southern pine (A) and commercial woodyplant IB) nurseries in the United States

Major soil tvpes

Soil property Sands to Loamy sands tol o a m y sands sandy loams

A’ B2 A’ B2

Silt loams toloams

A’ B2

Organic matter , o/u 1.5N, %, 0.07PH 5.3-5.8P, kg/ha 55-110K, kg/ha 85-140Ca, kg/ha 450-670Mg, kg/ha 55-65

Sources: ‘(11 ) , 2O ) .

*...... 2.0 . . . , . . . . . . >3.0 . . . . . . . . .. . . . . . . 0 . 10 . . . . . . . . . . 0 . 15 . . . . . . . . . .. . . . . . . 5.3-5.8 . . . , . . . . . . 5.3-5.8 . . . . . . . . . .15-30 85-l 10 30-40 85-140 40-8070-110 140-200 110-170 170-280 170-225

6 7 0 - 9 0 0 670-1,000 1,120-1,800 >l,OOO 2,240-4,480130 65-100 2 7 0 >lOO 540

69

NEUTRAL

I N C R E A S I N G A C I D I T Y I N C R E A S I N G A L K A L I N I T Y

VERY VERY VERYSTRONG STRONG MEDIUM SLIGHT SLIGHT SLIGHT SLIGHT MEDIUM STRONG

4.5 5 . 0 5.5 6 . 0 6.5

t

7.0 A 7.5 8.0 8.5 y

(COMMON pH VALUES OF SOILS(COMMON pH VALUES OF SOILS IN ARID OR SEMI-ARID AREAS1

IN MOIST 8 HUMID AREAS)

Figure 13-2.--&i/ values and their relationship to acidity and alkalinity. Taken from (9).

with pH values less than 7 are acid, and those withvalues greater than pH 7 are alkaline. The pH scale isa logarithmic one; thus, an increase or decrease of onepH unit means a tenfold change in acidity or alkalin-ity. For example, a soil with pH 5.0 is 10 times moreacidic than a soil with pH 6.0, but a soil with pH 4.0is 100 times more acidic than a soil with pH 6.0 (9).

Soil acidity has a strong influence on nutrientavailability in nursery soils or pot mixes. For exam-ple, macronutrients are readily available within arange of pH 6.0 to 8.0, but availability decreasesrapidly as pH value decreases (21). On the otherhand, Fe and Zn are almost unavailable if the soil pHis over 7.5 (fig. 13-31. Pine seedlings grow best in acidsoils ranging from pH 4.5 to 6.0. In soils with high pHvalues (>7.01, pine seedlings will develop a deep yel-low color because Fe is “unavailable” to the seedlings.

Where the soil is too acidic for plant growth, pHvalues can be raised by applying limestone. Amountsof limestone needed will vary according to the degreeof pH change desired, existing soil texture, organicmatter content, and form of limestone used. Theamounts of limestone needed to raise soil pH to 6.5 fordifferent textured soils having varying initial pH val-ues is given in table 13-5. When the pH value is toohigh, it can be lowered by applying acid-forming fer-tilizers (table 13-6).

Table 13-5.-Approximate amounts offinely ground pure limestone(kglha) needed to change acidity of an la-cm layer ofsoil l

Soil typepH change

4.5 to 5.5 5.5 to 6.5

Sand or loamy sand 6 0 0 900Sandy loam 1,100 1,550Loam 1,700 2,200Silt loam 2,700 3 , 1 0 0Clay loam 3,350 4,200

‘Values listed are “approximate” because amounts needed for agiven change are highly influenced by actual particle size and pu-rity of lime used as well as active and reserve acidity of the soilbeing limed. Source: (9).

Soluble salts should be monitored regularly. Manyspecies will not tolerate saline conditions and may beinjured by high levels of Na, B, and chlorides found inirrigation water. Fertilizer components can alsobreak down into soluble salts that accumulate innursery soil or potting medium.

Salt levels can be measured with a solu-bridge. Asample of soil is mixed with distilled water, and thesolution is tested for its ability to conduct electricity.Either a saturated paste or distilled water/soil dilu-tion methods (in 2:l or 5:l ratios) are used. Interpreta-

Table 13-6.-Ways of lowering soil pH value with acid-forming fertilizers’

FertilizerPet N

i nfertilizer

Kg of pure limestone needed to counteractacidity produced per -

45.4 ka of fertilizer 0.45 ke of N2

Ammonium ni trate 33-34 27.2 0.8Ammonium su l fa te 20-31 49.9 2.4Ammonium phosphate 16 39.9 2.4Urea 45-46 38.1 0.8Mono-ammonium phosphate 1 1 26.3 2.4Di -ammonium phosphate 21 33.6 1.6

Source (9 L“Values in this column are most important for judging fertilizer effectiveness: ammonium sul-

fate, ammonium phosphate, and mono-ammonium phosphate are three times as acid-forming asammonium ni trate and urea .

4.0 4.5 5.0 5.5 6.0 6,5 7.0 7.5 8.0 8.5 9.0 9.5 10.0PH

Figure 13-3.-Relationship of soil acidity and alkalinity to nutrient availability. Taken from (91.

tions of solu-bridge data are given in table 13-7. Irri-gation water can also be tested for excess salts usingsimilar methods. For nursery production, irrigationwater should have less than 250 micromhos/cm (9).

13.6 Fertilizers

Fertilizers are classified as inorganic or organic andnatural or synthetic (table 13-8). They can be single-or multi-element in composition and are available indry and liquid forms. Complete fertilizers have thethree primary elements, expressed as percentages ofelemental N, PzO, (phosphate), and KzO (potash).Thus, a label with 5-10-5 means 5% N, 10% Pz05, and5% KzO. In 1 kg this is 50 g of N, 100 g of PzO,, and50 g of KzO. Inorganic fertilizers may have acid, alka-line, or neutral reactions (table 13-9). Natural organicfertilizers or composts vary greatly in amounts of N,P, and K (1.3) (table 13-10).

Three alternatives for applying fertilizers are:. mix dry fertilizers directly with the growing

medium;. put soluble fertilizer solutions on the soil; or. formulate and use dry fertilizer mixes and soluble

solutions on site.

Each alternative has distinct advantages and dis-advantages, depending on whether field- or con-tainer-grown seedlings are produced.

13.6.1 Mixing Fertilizers With GrowingMedium. -This alternative is commonly used for dry(commercial) fertilizers applied before sowing ortransplanting. The fertilizer is placed in bags with potmedium or is incorporated with soil of bare-root beds.Mix proportions depend on whether soil test valuesare high or low and on actual fertilizer proportionsavailable in the mixes. Import restrictions may limitavailability of fertilizer mixes in some countries.

Dry fertilizers can also be broadcast by hand orapplied by machine with drills on larger areas or inbands between seedling rows. “Top dressing” alterna-tives are not suitable for containerized nurseries (19 ).Disadvantages are the trouble and high cost of mixingdifferent fertilizers and pot medium for differentstages of seedling growth (e.g., rapid growth phase vs.hardening-off phase) and the tendency of most slow-release dry fertilizers to raise medium pH value.Large traditional nurseries still incorporate fertiliz-ers with pot mix (15).

13.6.2 Using Soluble Fertilizer Mixes. -This alter-native is ideal for small nurseries needing minimal

71

Table 13-7.--Soluble salt levels in soils and irrigation water and their influence onplant groruth as determined by electrical conductivity’

Electrical conductivitsMillimhos/cm

Soils

Micromhos/cm Diagnosis

Less than 2 Less than 2,000

2 2,000

No adverse effect.

Yields of some salt sensitivecrops are affected.

Below 8 Below 8,000 Only moderately salt tolerantcrops can be grown.

8-16 8,000-16,000 Only salt tolerant crops canbe grown.

Above 16 Above 16,000 No profitable cropping possi-ble.

Irrigation water

0.1-0.25

0.25-0.75

0.75-2.25

Above 2.25

250-750

750-2,250

100-250 Low salinity: safe to use onpractically all crops andsoils, but some leaching isneeded to keep salts mov-ing downward; problemsmay develop on poorlydrained soils.

Medium salinity: mediumsalt tolerant crops areneeded; soils must be rela-tively permeable.

High salinity: only for salttolerant crops; adequatesubsurface drainage is es-sential, as is sufficientwater for leaching out ex-cess salts.

Above 2,250 Very high salinity: should notbe used for irrigation ex-cept under certain idealconditions (i.e., permeablesoil and/or tile drains forgood drainage, high waterrates for good leaching).

‘Source: (9 ).

72

Table 13-B.-Chemical and physical properties of fertilizers’

Chemical properties

A. State:1. Organic:

(a) Natural(b) Synthetic

Physical properties

A. State:1. Dry:

(a) Pulverized(b) Granular (prills)(cl Tablet(d) Packet(e) Encapsulated

2. Inorganic: 2. Liquid:(a) Natural (a) Water-soluble(b) Synthetic (b) Suspension

B. Element:1. Single2. Double3 . Triple (complete)4 . Multi

B. Release rate:1. Rapid2. Slow (controlled)

C. Long-term effect on soil acidity:1. Acidic (lowers pH value)2. Neutral3. Basic (raises pH value)

‘Source: (3 ).

Table 13-9.-Element content, reaction, and solubility of common fertilizer chemicals’

Commonfertilizer

nameChemicalformula

Fraction of element in compound (X 100 = %l

(NOs) (NH41 p K s Ca Mg Long-term SoiubilitysN N reaction2

Potassium nitrate KNOs 0.139 0.386Ammonium nitrate NH4N0s 0.175 0.175 Acid HighCalcium nitrate Ca(N0s12.4H20 0.119 0.169 Base MediumDiammonium phosphate (NH412HP04 0.212 0.235 Acid LowAmmonium sulfate (NH4)2S04 0.212 0.242 Very acid HighNitric acid HNOs 0.222 Very acid HighOrthophosphoric acid H3P04 0.316Potassium metaphosphate KP03 0.228 0.287Concentrated superphosphate Ca(HsPO&HsO 0.246 0.159Potassium carbonate K2CO3 0.565Calcium-magnesium

carbonate (dolomite) CaCOs.MgCOs 0.217 0.130Magnesium sulfate MgS04.7H20 0.130 0.097Potassium sulfate K2S04 0.448 0.184Sulfuric acid H2S04 0.326Meta phosphoric acid P20s.H20 0.437Potassium oxide

(potash) K20 0.830

‘Adapted from (191.2Missing data were not available.

73

Table 13-lO.-Average nutrient content of fresh animal manures before compost-iflgl

Nutrientor

elementCatt le Chicken Horse Sheep Swine

_______________________ percent _________-_____________Nitrogen (N) 0.53 0.89 0.55 0 .89 0.63Phosphorus (PzO5) 0.29 0.48 0.27 0 .48 0 .46Potassium (KaO) 0.48 0.83 0.57 0.83 0.41Calcium tCa) 0.29 0.38 0.27 0.21 0 .19Magnesium tMg) 0.11 0.13 0.11 0.13 0.03Copper ( Cu) 0.00079 0.0006 0.00079 0.00079 0.00016Manganese (Mn ) 0.003 0.003 0.003 0.003 0.0008Zinc (Zn) 0.0016 0.0021 0.002 0.002 0.0006Chlorine (Cl) 0.03 0.08 0.08 0 .08 0.03Sulfur LS) 0.036 0.06 0.036 0.06 0.03Boron (B) 0.016 0.016 0.016 0.016 0.0005Organic matter 16.74 30.70 27.06 30.70 15.50Moisture 18.33 64.82 68.85 64.82 77.56Ash 2.06 4.72 6.70 4.72 6.02

‘Since moisture percentage of any manure is highly variable, indicated nutrientpercentages are general values. Source: I 9 I.

amounts of fertilizer or for very large nurseries hav-ing good irrigation equipment (2). Commercial pow-ders or granules are dissolved in water, and solutionsare applied to seedlings with hand-pump sprayers orare injected into irrigation systems. This method isadaptable to nurseries growing several species. How-ever, what works in one location might not work wellin another because of differences in local water qual-ity, inherent chemical properties of nursery soils andpot medium, and existing environmental factors. Sys-tems should be tested on small plots before they areused operationally.

Commercially formulated soluble fertilizers areeasily prepared with minimal instructions or precau-tions. Some drawbacks can be: insufficient knowledgeabout the “carrier” or chemical compounds used tosupply the nutrient ions; use is limited to the nutrientproportions available in the mixes; salts used as nu-trient carriers can modify soil solution acidity, requir-ing a separate pH adjustment; and workers preparingsolutions cannot easily compensate for Ca, Mg, or mi-cronutrients that are naturally available in localwater supplies, thus risking the possibility of addingexcess salts.

13.6.3 Formulating Nutrient Solutions on Site. -This alternative involves making “homemade” fertil-izer solutions to be applied by hand sprayers or in-jected into irrigation systems. Technical gradechemicals are added to water according to a formulaadjusted for local water supplies and the speciesgrown. Homemade solutions are not practical forsmall nurseries. However, they are very cost effectivefor large, highly mechanized container systems wheremanagers have ready access to chemical compoundsand need to tailor their fertilizers to particular crops,pot mixes, and water composition.

Disadvantages of homemade solutions are: the usermust be trained in chemistry and be able to handlehazardous materials carefully and safely; large stocksof chemicals must be safely stored, identified, andweighed before mixing; opportunities for mixingerrors are greatly increased over those encountered inusing premixed fertilizers; and, when optimum con-centrations are unknown, fine tuning of the formula-tion is time consuming and requires technical exper-tise.

Appendix 13 gives hints and methods for mixingcommercial fertilizers. Other important consider-ations for correct fertilizer application are timing, i.e.,not too wet or too dry (18); interaction effects betweenspecies and fertilizers (16 1; type of soil being fertil-ized, i.e., not all soils respond to fertilizer additions(17); and age/health status of seedlings (4) being fer-tilized.

LITERATURE CITED

1 . Ballard, R.; Pritchett, W. L. Utilization of soil andfertilizer phosphorus compounds by slash pineseedlings in relation to their solubility in soiltest extracts. In: Proceedings, Soil Science Soci-ety of America; 1975; 39: 537-540.

2. Belanger, R. P.; Briscoe, C. B. Effects of irrigatingtree seedlings with a nutrient solution.Caribbean Forester. 24(2): 87-90; 1963.

3. Davidson, H.; Mecklenburg, R. Nursery manage-ment administration and culture. EnglewoodCliffs, NJ: Prentice Hall, Inc.; 1981. 450 p.

4. Donald, D. G. M. The use of slow-acting fertilizersin the production of Pinus radiata nurseryplants. Communication 59. Mededeling, SouthAfrica: Faculty of Forestry, University of Stel-lenbosch; 1973. 12 p.

5. Epstein, E. Mineral nutrition of plants: principlesand perspectives. New York: John Wiley andSons; 1973. 412 p.

6. Lamb, D. Variations in the foliar concentrationsof macro and micro elements in a fast-growingtropical eucalypt. Plant and Soil. 45: 447-492;1976.

7. Lamb, D. Relationships between growth and fo-liar nutrient concentrations in Eucalyptus de-glupta. Plant and Soil. 47: 495-508; 1977.

8. Leaf, A. L. Plant analysis as an aid in fertilizingforests. In: Walsh, L. M.; Beaton, J. D., eds. Soiltesting and plant analysis (rev. ed.) Madison,WI: American Society of Agronomy, Inc.; 1973:427-454.

9. Leonard, Dave. Soils, crops 8z fertilizer use or awhat, how, and why guide. 3d ed. InformationCollection and Exchange Reprint RB. Washing-ton, DC: Peace Corps. 1980. 162 p.

10. Liegel, Leon H. Seasonal nutrition of 3- and 4-year-old Pinus caribaea foxtails and normal-branched trees in Puerto Rico. Ph.D. disserta-tion. Raleigh, NC: North Carolina StateUniversity; 1981. 141 p.

11. May, Jack T. Nutrients and fertilization. In:Lantz, Clark W., ed. and camp. Southern pinenursery handbook. Atlanta, GA; U.S. Depart-ment of Agriculture, Forest Service, SouthernRegion; 1984: 12-1 to 12-42.


13. Simpson, J. A. Nursery nutrition studies withslash pine at Beerburrum. Queensland Res.Pap. 9. Brisbane, Queensland, Australia: De-partment of Forestry; 1978. 32 p.

14. Simpson, J. A. Use of inorganic fertilizers andcover crops in exotic pine nurseries of southernQueensland, Australia. In: South, David B., ed.Proceedings, international symposium on nurs-ery management practices for the southernpines; 1985 August 4-9; Montgomery, AL.Auburn AL: School of Forestry, Alabama Agri-cultural Experiment Station, Auburn Univer-sity; 1985: 203-212.

15. Solberg, Karl H. A nursery and field experimentwith various potting soils and fertilization.Pinus caribaea, Tanzania. EAC/NORAD low-land afforestation project Tech. Rep. 9, Aas,Norway: Department of Silviculture, Agricul-tural University of Norway INLH,; 1978. 49 p.

16. Solberg, Karl H. A transplanting and fertiliza-tion experiment. Pinus caribaea, Tanzania.EAC/NORAD lowland afforestation projectTech. Rep. 6. Aas, Norway: Department of Sil-viculture, Agricultural University of Norway(NLH,; 1978. 18 p.

17. Solberg, Karl H.; Lysholm, Gunnar. Miscella-neous nursery experiments with Pinus carib-aea and P. oocarpa in Gede nursery, Kenya.EAC/NORAD lowland afforestation projectTech. Rep. 1. Aas, Norway: Department of Sil-viculture, Agricultural University of Norway(NLH); 1978. 55 p.

18. Theron, J. M. Nursery research in Malawi 1964-1971. Res. Rec. 56. Zomba: Malawi Forest Re-search Institute; 1972. 43 p.

19. Tinus, Richard W.; McDonald, Stephen E. How togrow tree seedlings in containers in green-houses. Gen. Tech. Rep. RM-60. Ft. Collins, CO:U.S. Department of Agriculture, Forest Serv-ice, Rocky Mountain Forest and Range Experi-ment Station; 1979. 256 p.

20. Tisdale, Samuel L.; Nelson, Werner L. Soil fertil-ity and fertilizers. New York: MacMillian,1975. 694 p.

21. Truog, Emil. The liming of soils. In: The yearbookof agriculture, 1943-47. Washington, DC: Gov-ernment Printing Office; 1947. 944 p.

22. Tschinkel, H. M. Growth, site factors and nutri-tional status of Cupressus Zusitanica planta-tions in the highlands of Colombia. Ph.D. dis-sertation. University of Hamburg. Hamburg,Federal Republic of Germany; 1972. 165 p.

23. Van den Driessche, R. Soil fertility in forest nurs-eries. In: Duryea, Mary L.; Landis, Thomas D.,eds. Forest nursery manual: production of bare-root seedlings. The Hague, The Netherlands:Martinus Nijhoff/Dr W. Junk Pub.; Corvallis,OR: Forest Research Laboratory, Oregon StateUniversity; 1984: 75-80.

24. Youngberg, C. T. Soil and tissue analysis: toolsfor maintaining soil fertility. In: Duryea, MaryL.; Landis, Thomas D., eds. Forest nurserymanual: production of bareroot seedlings. TheHague, The Netherlands: Martinus Nijhoff/DrW. Junk Pub.; Corvallis, OR: Forest ResearchLaboratory, Oregon State University; 1984:75-80.

CHAPTER 14

14. NURSERY EXPERIMENTATION

14.1 Planning the Experiment

Experiments are important in permanent nurseriesbecause they produce information for managerial ortechnical guidelines (28 ). For example, experimentscan indicate whether top dressed granular or liquid Nfertilizer is best for a particular bare-root nursery in

75

a wet climate. Experiments may also indicate whichof several locally available postemergent herbicidesgives the longest coverage in comparison with tradi-tional hand weeding.

Experimentation is often excluded from nurseryand reforestation efforts because its purpose is misun-derstood or because it is confused with statistics. Ex-perimentation is the systematic observation, classifica-tion, and analysis of facts and data; it emphasizes thewhy and how of what is done. Statistics, on the otherhand, are mathematical measures that describe orga-nized raw experimental data. The most commonlyused measures are the mean, standard deviation,variance, and coefficient of variation.

Commonly used statistical measures are given intable 14-1. A hypothetical experiment is explainedhere to illustrate how experimentation is importantfor effective decision making in reforestation projects.

14.1.1 Traits Assessed. -Experiments can be donein the nursery or in the field. Many measurementtraits or variables can be measured or assessed. Ex-amples (2, 5) are:

SeedlSeedling Traits

Average seed weightand size

Mean germinationtime for seeds

Percentage of seedsgerminated withinstated periods oftime

Number of cotyledons

Seedling height incentimeters, atstated periods oftime or before lift-ing

Seedling root collar di-ameter in millime-ters, using calipers

Seedling survival, inpercent, at differentgrowth stages ofnursery

Containerllrrigation Traits

Container volumes in ta-pered and non-taperedcavities and their influ-ence on root develop-ment

Potting mix proportions of20, 40, and 60 percentpeat and their influenceon seedling growth

Hand- and mechanically-seeded containers andtheir effects on seedlinggrowth

Overhead versus sidesprinklers and theireffects on reducingseedling mortality frompersistent drip

In each instance, events or traits are recorded ac-cording to previously formulated plans and designs(11). In a few cases, unusual phenomena are also re-ported (15, 17).

14.1.2 Sources of Vuriation. -Nurseries generallyhave less environmental variation than do field sites.Nurseries occupy small areas within which skilledresearchers can control light, temperature, soil mois-ture, soil nutrients, and soil aeration more easily thanon larger field sites. Small amounts.of plant materialsused in nursery research are also less variable thanare larger amounts of field planted materials. Excep-tions occur when individual plants are used as treat-ments. In such cases, plant-to-plant variation, partic-ularly in yield, may be great. Averaging many plantstogether to obtain treatment values avoids excessivevariation (e.g., grinding up 10 seedlings-not l-pertreatment replication to obtain shoot/root ratios ofseedlings grown in one type of container having dif-ferent pot volumes).

Investigators studying nursery and greenhouse ex-perimental designs (4, 6, 8) have identified severalsources of variation:l temperature differences around benches caused by

steam pipes and proximity to doors, ventilators,and exhaust fans;

l shading effects from nursery structures and sur-rounding trees;

. moisture differentials caused by air currents (drift)and clogged irrigation nozzles;

. non-uniformity of physical and chemical propertiesof pot medium caused by using medium preparedin different production runs; and

. changing light intensity and duration as growingseasons change.

Properly designed research trials avoid such vari:, -tion whenever possible or at least account for it b,adequate replication.

14.1.3 Experimental Procedures. -An overall re-search plan is essential when conducting experi-ments. It should always answer: Who? Why? What?Where? When? How? and How much?

The first step is outlining the objectives and ques-tions to be answered. Always restrict objectives to afew simple ones. Written objectives and a writtenwork plan are critical for maintaining longer trialsthat continue after their originator has left.

Consider a postemergent herbicide trial to controlweeds in bare-root pine seedbeds. Two importantquestions are: which herbicide controls weeds for thelongest time without reapplication? Are the herbi-cides used non-toxic for the pine species tested? Obvi-ously, all herbicides and pine species cannot be tested.How, then, does one limit the scope of the proposedherbicide trial?

14.1.3.1 Restricting Experiment Objectives.-Re-stricting the objectives can be done by consideringdata on herbicides from elsewhere, including local re-sults from agricultural or horticultural trials. Localproduct availability can limit the herbicides eventu-ally chosen for testing. After reviewing available in-

76

Table 14-l.-Summary statistics for two data sets

Stat i s t ic ’Data set I Data set II

A B C AI Bl Cl

8 5 1 8 5 18 6 2 9 7 59 8 5 9 9 8

10 10 10 10 10 101 1 12 15 10 1 1 1212 14 18 1 1 1 3 1512 15 19 12 15 19

S u m 70 70 70 i-6 70 iiMean W 10 10 10 10 10 10Standard

dev ia t ion (s) 1.7 3.9 7.5 1.3 3.4 6.1Variance (s2) 2.9 15.2 56.2 1.7 11.6 37.2Coeflicient of

variation (CV-%) 17 3 9 75 13 34 61

‘IL-The sum of individual observations divided by total number (n) of observations in a sampleor set of values. Each of the six data groups has an n of 7 (observations); thus, each of thesix sums is divided by 7 to obtain the mean.

s-A summarization unit for interpreting whether individual observations are clusteredaround or spread away from the mean. Symbolically it is calculated:

For group A of Data Set I:

(812 + (8j2 + (9)2 + (1O)2 + (1112 + (1212 + (1212 -q = 1.7

6

Group A has the lowest s in Data Set I; thus, observations in group A are very clusteredaround the mean of 10. Observations in Data Set II are all more clustered around theirmeans, since the s of groups in Set II are all lower than those in Set I.

s2-The square of s, or for data group A (1.7j2 = 2.9. Statisticians use s2 in analysis of variancefor testing whether various treatments are significantly different from one another.

CV-It i s used to eva luate resu l t s f rom severa l exper iments measur ing the same var iable ortrait. It is calculated:

CV = i x 100; for data group A,

g x 100 = 17.

In field experiments, CV values usually range from 15% to 50%; ~15% in nursery exper-iments. If values are higher, there was too much variability in plant materials or site andnursery conditions, and the experiment must be done again.

formation, one might decide to test different concen-trations of one locally available herbicide on the mostpromising pine species for reforestation. A concisestatement of experiment objectives would be:

“To determine the effect of three concentrations(high, medium, low) of Goal herbicide and hand weed-ing (control) on weeds common in P. caribaea var.hondurensis bare-root seedbeds.”

The traits assessed could be: coverage, or the maxi-mum number of days between first and subsequentapplications needed to control (kill) weeds; seedlingheight and root collar growth and survival at specifictimes (2, 4, 6, and 8 months) in all beds where herbi-cides are applied and in hand-weeded control plots;and seedling damage for all treatments and the con-trol over the duration of the experiment (i.e., some

herbicide concentrations may be selectively toxic tocertain pines and hardwood species).

14.1.3.2 Replicating the Experiment. -If a forestrycompany performs the experiment, it may conducttrials at two or more nurseries that it owns. This isbeneficial because site conditions, particularly soilproperties, may be dissimilar at the different sites. Ifherbicide coverage is related to site properties, thecompany should know this for long-term planning.Replicating the experiment is rather simple becausethe nursery locations are fixed in this example. Inspecies adaptability trials, potential trial sites are al-most infinite. Thus, in field research, it is usuallydifficult to choose (at random) small experimentalareas that are typical of large areas that will be refor-ested.

7 7

A word of caution! Confounding two or more factorsmust be avoided. For example, if one conducts nurseryexperiments at two or more sites, major operationalactivities at each are assumed to be identical, whetherthey be sowing, undercutting, watering, or applyingherbicides. Using different equipment and equipmentoperators having different levels of skill at two ormore nurseries can influence seedling growth and de-velopment in significant ways that have nothing to dowith herbicide treatments. When such differences aresignificant, confounding has occurred. Interpretationof research results is impossible when unplanned con-founding occurs.

14.1.3.3 Randomly Assigning Treatments. -Thelast step is establishing the herbicide experiment inpredetermined areas within the two nurseries. Toavoid confounding, sites as uniform as possible arechosen at each nursery. Certain experimental designstake into account unidirectional or bidirectional sitegradients that cannot be avoided (Sec. 14.2). What-ever the design chosen, all treatments (herbicides andcontrol plots) are assigned randomly to all blocks. Ifnot, some treatments will always appear next to oth-ers with possible confounding effects.

In summary, experimentation is an important, in-tegral component of decision making in nurseryprojects. When conducting experiments, follow thesethree cardinal rules (the 3 R’s) (1):

1. Restrict objectives to simple and manageableones.

2. Replicate research plots on several sites if possi-ble, and in several blocks at each site.

3. Randomly assign treatments to each experimen-tal block at each site.

14.2 Experimental Design Considerations

24.2.2 Plot Shape. -Regular, compact experimen-tal blocks have less microsite variation and are pre-ferred over irregular shaped ones (fig. 14-l). Whenknown moisture or other variation exists at a fieldsite, place the long side of blocks parallel to the gradi-ent (fig. 14-2). Sometimes, outside factors will dictateblock shape and orientation, e.g., location of nurseryroads and buildings (fig. 14-3). Making blocks or plotsa convenient portion of a hectare (e.g., 0.01 or 0.02)simplifies converting raw data to a whole hectarebasis.

24.2.2 Hot Size.-Optimum plot size depends onseveral factors, including available land, numbers ofseedlings tested (i.e., some may be sacrificed or lost),seedbed spacing or container cavity density, and ex-periment duration. For example, nursery trials as-sessing hypocotyl color and chlorophyll content of pri-mary and secondary needles require many seedlingsbecause traits are highly variable (13, 14 ). Con-versely, if only mean seedling height and root collar

78

mm”

DESIRABLE EXPERIMENTAL BLOCK SHAPES

( R E G U L A R 8 COMPACT)

UNDESIRABLE EXPERIMENTAL BLOCK SHAPES

( IRREGULAR 8 NON-COMPACT) v

Figure 14-l.-Desirable and undesirable plot shapes for forestryexperimentation.

diameter are assessed at different phases of nurserydevelopment, fewer seedlings and smaller plot sizesare used (16).

14.2.3 Border, Surround, or Edge Rows. -Edges ofseedbeds are more exposed to light, wind, and nutri-ents (excluding container cavities) than are interiorrows. Thus, seedlings (or grasses in fallow studies) inedge rows are not assessed in nursery trials becauseestimates of height growth and other traits may bebiased, upwards or downwards, from estimates of in-terior seedlings (10). Leaving out one or more edgerows, depending on seedling density and plant mate-rial availability, is common for nursery experiments.

14.2.4 Number of Replications. -Fewer replica-tions (blocks) are needed in a nursery than in fieldtrials (Sec. 14.1.2). Two or three replications are theminimum number for most nursery experiments; fourto five replications are the minimum for field trialsand nursery experiments where there is a large vari-ation in sites or plant materials. When nursery stud-ies are outplanted, the same replication and random-ization scheme should be followed.

14.2.5 Experimental Designs. -The four mostcommonly used experimental designs in nursery re-search are described below, including discussion of:when a particular design is appropriate and the as-sumptions involved, its advantage over other designs,its limitations and restrictions, and a practical exam-ple for its use. Basic texts on statistics (3, 7, 9, 12)contain instructions on calculating sums of squaresand error mean squares for analysis of variance andmultiple comparison tests of treatment means. Facto-rial experiments are omitted because they are more

b d

d

b

d b

I, II, Iu - EXPERIMENTAL BLOCKS

a -LOW DOSAGE HERBIC IDE

b - MEDIUM DOSAGE HERBICIDE

C - HIGH DOSAGE HERBICIDE

d - CONTROL ( I .E . , HAND WEEDING)

Figure 14-2.-Appropriate randomized complete block design fornursery experiments where site gradient is in one di-rection.

complicated in theory, implementation, and analysis.14.2.5.1 Completely Random. -When experimen-

tal conditions and materials are quite uniform, a com-pletely random design is used. It is simple to set upand analyze data obtained. There are no restrictionson the number of replications and treatments. In theexample shown in figure 14-4, four fungicides (A, B,C, and D)are tested to control damping-off in germi-nating trays. Sixteen trays with seeds are preparedand randomly assigned to a particular treatment. Thetrial lasts as long as normal germination continues.This design assumes that all trays have the samegerminating medium, are seeded with the sameamount of seeds from similar lots (having equal per-centages of germination), and are watered and tendedequally. Also, it assumes that there are no changes intemperature, light, etc., from bench A to bench D.

14.2.Fi.2 Randomized Complete Blocks.-Whenvariation exists in one direction, the randomized com-plete block design requires fewer replications and ismore precise than a completely random design. Ad-

WARD-SURFACED MAJOR ROAD

SECONDARY DIRT ROAD FOR ACCESS TO NURSERY

ORAVEL ROAD FOR ACCESS TO NURSERY

Figure 14-3.-Outplant design for nursery site that is affected bvphysical constraints that place four beds on east andfour beds on west side of major access road to nurs-e r y .

I0A

0

A

0

B

0

c

2

0

C

I7

B

17

A

El

B

3

I7

C

0

D

qB

0

D

4

El

A

cl

D

0

D

0

c

1.2.3.4 - N URSERY BENCHES

A,B,C,D - FOUR FUNGICIDES (ONE PER EACH SEED-GERMINATION FLAT)

Figure 14-4.--Completely random experimental design for compor-ing effects of four fungicides (A, H, C. and 111 oncontrotting damping-o/f in pine germinalion f/ats.

79

vantages of randomized complete blocks are: simpleinstallation and easy data analysis, even when thereare missing or lost plots. The design is not appropriatewhen: within-block variation is great, blocks interactwith treatments, or the number of treatments is large.The major restriction is that the same treatments areapplied in each block.

For example, figure 14-5 shows the herbicide trial,adapted to a site where moisture and fertility varia-tion exist. Each row and column has all four treat-ments (three herbicides plus hand-weeded control).All tending operations are assumed to be the same foreach plot.

Figure 14-2 shows a randomized complete block lay-out for the herbicide trial mentioned in Section14.1.3.1. Long sides of Blocks I, II, and III are placedparallel to a known moisture gradient. Within eachblock, the four treatments are randomly assigned.Note that the “control” is a hand-weeded plot, not ano-weeded plot. If a plot is not weeded, weeds in it caninvade adjacent plots, limiting the effect of herbicides.

14.2.5.4 Split Plot.-This design is used when sometreatments are best applied to large plots and othersto small plots. In practice, this means establishinglarge plots first, then splitting them into small plotsto which minor treatments are assigned randomly.

Bed preparation techniques and tending opera-tions, particularly watering, are assumed to be thesame. Other within-block site variation must be min-imal (no residual nutrient gradient from past fertil-izer or fallow treatments).

Figure 14-6 shows a split-plot design to test theeffects of two potting mixes and three seeding proce-dures on germinating pine seed in containers.Medium 1 (Ml) is a 1:l mixture of peat and vermi-culite; medium 2 (M2) is a 1:l mixture of local compostand vermiculite. Sowing operations are direct (hand)seeded (Sl), fully automated by vacuum plate (S21,and semi-automated box seeder (S3); two seeds aresown per cavity.

14.2.5.3 Latin Square. -When site variation exists Because of variability in seeding operations, fivein two directions, the latin square design is used. Its replications are used. Traits assessed are: time foradvantages are: control of experimental error in two each seeding (small plot) treatment to obtain 90 per-directions and the ability to omit columns or rows cent germination, total number of seeds germinatedfrom analysis because of excessive plot mortality or in 3 weeks, percentage of full cavities (i.e., at least onedamage. The major disadvantage or restriction is that seedling per cavity), and mean height of germinantsthe treatment number must be equal to the number of after 3 weeks for each seeding treatment on eachrows and columns in the design. This usually restricts growth medium. Watering, damping-off control, shad-treatments to 10 or less. ing, etc., are assumed to be equal for all containers.

o A

- t -C e

A C

--I--B Q

C O L U M N S

A

GREATER SOIL MOISTURE4

A - CONTROL (I.E.. llANO-WEEDED)

B - LOW HERBICIDE DOSAGE

C - MEDIUM HERBICIDE DOSAGE

D - HIGH HERBICIDE DOSAGE

MI M2

53 ss

is

52 SI

SI 52

M2 M I51 52q 1

32 s 3

Sb SI

M I M2

91 SI

s3 s2

s 2 53

INDIVIDUAL.STVROBLOCK

CONTAINER

MI - ,:I MEOIUM MIXTURE OF SI - HAN0 DIRECT-SEEDEDPEAT/VERMICULITE

M2- 1’1 MEDIUM MIXTURE OFCOMPOST/VERMICULITE

j2- FVLL” AUTOMATICVACUUM-SEEDED

S3 - S E M I - A U T O M A T I CPLATE-SEEDED

14.8 Data Recording and Record Keeping

Accurate record keeping is essential for evaluatingexperiments. Insufficient data or improperly recordeddata will prevent experimental questions from beinganswered adequately. Thus, experiment work plansshould include data-sheet examples of the nurserytraits assessed (fig. 14-71, instructions on how and

when assessments will be made, and guides on sum-marizing raw field data. Also, each study should haveits own experimental design, clearly indicatingblocks, replications, and position sequence for treeslocated in seedbeds.

Individual items may seem trite, but many experi-ments have been lost because sowing, tending, ormeasurement dates were not recorded or were

Study name/number Block No. Rep. No.

Assessment date

Tree Root co1 larNO. diameter

Height Tree Root collarNo. diameter

Height Tree Root collar HeightNo. diameter

:345

;89

101 112131415161718

:i

4142434445

:;

250

::

:i5556

z;

;i

Notes Total No. Living

- - - - - Means - - - - -

I I

Root Collar Seedling Root Collar Seedling Root Collar Seedlingdiameter Height diameter Height diameter Height

(ml) (cm) hm) (cm) (mn) (cm)Nos. 1 to 20 Nos. 21 to 40 Nos. 41 to 60

Summary I Age I N -D Ti % SurvivalI

N = Seedlings surviving at assessment.B = Mean root collar diameter (i.e., arithmetic mean of all surviving seedlings).H = Mean height (i.e., arithmetic mean of all surviving seedlings).% Survival = No. of seedlings surviving at assessment

No. of seeded cavities in Styroblock

Figure 14-7.-Example of a field data sheet for nursery research.

81

recorded illegibly. Below is a list of procedures thatresearchers should follow when recording data.

14.3.1 Data Recording Do’s and Don’ts. -No mat-ter what format is used, ALL DATA SHEETSSHOULD CONTAIN:

1. Species or provenance planted and trait as-sessed.

2. Date of assessment-the month and day shouldbe written out instead of using a numberingsystem that is not uniform throughout theworld (e.g., November 4, 1982 instead of 1114182, which is also written as 4111182). Record-ing the exact date is critical for calculatingseedling and tree growth rates in tropical re-gions where a dormant season is absent.

3. Names of person(s) who made the assessmentand the traits they were responsible for (e.g.,John Doe: seedling heights, Jane Doe: datarecorder).

4. Notations on whether data are in metric or En-glish units.

5. Complete identification codes for all treatments,including block and plot numbers for repli-cated experiments.

6. A separate column for unusual things observedin any plot or at the research site (e.g., insectattack, wind damage, or persistent drip dam-age from irrigation lines).

7. Numbers that are clearly and distinctly writ-ten-handwriting differs from one person toanother, but if numbers are not recordedclearly, summarization by someone other thanthe recorder may be impossible.

8. Results of data that are summarized and ana-lyzed as soon as possible after they were ob-tained-waiting months or years is not recom-mended because data become “cold” andinconsistencies are not caught in time.

Finally, before leaving the nursery, check that ap-propriate items have been completed on all datasheets and that assessment dates appear on each page.Catching errors and correcting them before returningto a distant office can save a l-day trip back to thenursery site; simple omissions or inconsistencies canbe spotted and corrected if accuracy is constantlychecked.

14.3.2 Basic Statistics and Data Summariza-tion. -Simple statistics used to summarize data fromnursery experiments are the mean, standard devia-tion, variance, and coefficient of variation. A defini-tion for each and an example of its calculation isshown in table 14-1.

Summarization of raw data, especially when donewith a computer, is simple if the data are coded cor-rectly on data sheets. One example is shown in figure

14-7. Formats will vary, depending on the study de-sign and traits assessed. Each sheet should be devel-oped well ahead of any measurement to ensure itsease of use and versatility.

LITERATURE CITED

1. Briscoe, C. B. Ensayos de plantation estadistica-mente validos. Caribbean Forester. 22(3-4):64-68; 1961.

2. Burely, J.; Wood, P. J. Manual sobre investiga-ciones de especies y procedencias con referenciaespecial a 10s tropicos. Tropical Forestry Papers10 and 10A. Oxford, UK: Oxford Press. Com-monwealth Forestry Institute, Department ofForestry; 1979. 63 p.

3. Cochran, W. G.; Cox, G. M. Experimental designs.New York: Wiley Publ. Co.; 1957. 611 p. 2d ed.

4. Cox, G. M.; Cochran, W. G. Designs of greenhouseexperiments for statistical analysis. Soil Sci-ence. 62: 87-98; 1946.

5. Faulkner, R. Procedures used for progeny-testingin Britain with special reference to forest nurs-ery practice. Forestry Commission ForestRecord 60. London: Her Majesty’s StationeryOffke; 1967; 22 p.

6. Federer, W. T. Plot technique in greenhouse ex-periments. Proceedings, American Society ofHorticulture Science; 62: 31-34; 1953.

7. Freese, Frank. Elementary statistical methodsfor foresters. Agric. Handb. 317. Washington,DC: U.S. Department of Agriculture; 1967.87 p.

8. LeClerg, E. L. Factors affecting experimentalerror in greenhouse pot tests with sugar beets.Phytopathology. 11: 1019-1025; 1935.

9. LeClerg, E. L.; Leonard, W. H.; Clark, A. G. Fieldplot technique. Minneapolis, MN; BurgessPubl. Co.; 1962. 372 p. 2d ed.

10. Liegel, L. H. A need for better design and analysisof adaptability, provenance, and spacing trialsof exotic trees in tropical areas-with examplesfrom Puerto Rico. Raleigh, NC: North CarolinaState University; 1976. 27 p. Unpublishedpaper.

11. Nelson, Larry A. Tecnicas de parcelacion ydisenos experimentals: principios y aplica-ciones. Raleigh, NC: Statistics Department,North Carolina State Univeristy; 1977. Pagi-nation varies.

12. Steel, Robert G. D.; Torrie, James H. Principlesand procedures of statistics. New York:McGraw-Hill; 1960. 481 p.

13. Venator, C. R. Hypocotyl length in Pinus caribaea

82

seedlings: a quantitative genetic variationparameter. Silvae Genetica. 23: 130-132; 1974.

14. Venator, C. R. Hypocotyl color: evidence for poly-morphism in Pinus caribaea. Turrialba. 26(3):265-267; 1976.

15. Venator, C. R. A mutant Pinus caribuea var. hon-durensis seedling incapable of developing nor-mal secondary needles. Turrialba. 26(l): 98-99;1976.

16. Venator, C. R. Natural selection for drought re-sistance in Pinus caribueu Morelet. Turrialba.26(4): 381-387; 1976.

17. Venator, C. R. Formation of root storage organsand sprouts in Pinus oocurpu seedlings. Turri-alba. 27(l): 41-45; 1977.

18. White, T. L. Designing nursery experiments. In:Duryea, Mary L.; Landis, Thomas D., eds.Forest nursery manual: production of barerootseedlings. The Hague, The Netherlands: Marti-nus Nijhoff/Dr W. Junk Pub.; Corvallis, OR:Forest Research Laboratory, Oregon State Uni-versity; 1984: 291-306.

CHAPTER 15

15. MECHANIZED CONTAINERPRODUCTION

15.1 Criteria for Selecting Containers

To select a suitable container, nursery managersmust answer several questions. What is the minimumcontainer volume needed for high seedling outplant-ing survival? Which containers provide this volume?What are delivery costs for the containers havingthese volumes? And, what are anticipated overhead(wages, administration, and facility depreciation) anddirect (temporary labor, fuel, fertilizer, and pesticide)costs.

Of the many kinds of containers having the sameeffective root volume, some are reuseable; those notreuseable represent overhead or direct costs. Also,freight charges and import duties in overseas coun-tries can be high for “bulky” containers. Factors af-fecting container volume and the major kinds of con-tainers used are discussed below; other authors treatthe same topics in greater detail Cl, 5, 14, 22). Withthis information, managers can select the “optimum”container for their needs and decide whether it is bestpurchased locally or elsewhere.

15.2.2 Length. -Before 1970, lack of research datamade it difficult to select optimum container length.Today, data show that optimum container volume isclosely dependent upon length (21, 23 1. In general,short containers, 13 to 15 cm long, are best for areashaving long wet seasons. Long containers, 20 to 25cm, are best for areas having irregular and long dryspells where seedling root systems must be placeddeeper into the soil to avoid rapid desiccation.

15.1.2 Shape. -The most common cross-sectionalshapes are round and square. Container configurationis important because of its relationship to total vol-ume. For example, a box container 5 by 5 by 20 cm insize has a volume of 500 cm3; a round container 5 cmin diameter and 20 cm long has a volume of 392 cm3,22 percent less volume. Nursery benches and plantingboxes can hold equal numbers of each container be-cause of their geometrical design (fig. 15-l). Some con-tainers are tapered at the bottom, reducing effectivevolume for a given length (fig. 15-2). Hexagonalshapes are common in expandable paperpots.

15.1.3 Volume/Design Influences on Roots.

15.1.3.1 Ribs.-Container design influences rootformation and root growth pattern. Four or more in-ternal vertical ribs (fig. 15-3) direct roots downwardand prevent root spiraling within containers. Round,rigid containers usually have ribs that make themsuperior to non-ribbed containers.

15.1.3.2 Holding Time. -Container volume influ-ences the length of time that seedlings are held in thenursery once they reach outplanting size. For smallvolume containers, holding time decreases, and forlarge volume containers, holding time increases, al-lowing more flexibility to accommodate plantingschedules. Keeping seedlings for long periods afterroots have reached the container bottom creates un-balanced root/shoot ratios, J-roots and spiraled roots.After they have reached outplanting size, seedlingsshould not be held more than 45 days when usingsmall volume containers (~300 cm31 and not morethan 75 days when using large containers (>550 cm3).

15.1.3.3 Drainage/Root Egress Openings. -Open-ings at bottom and sides of containers keep potmedium adequately drained. Bottom holes allow rootegress and prevent root spiraling at container bottoms(fig. 15-4). Openings must be large enough to allowfree drainage and root egress when necessary, and yetsmall enough to prevent loss of pot medium in filling,handling, and stacking operations.

25.2.4 Container Construction Materials. -Help-ful questions to ask when considering ideal containerconstruction materials are: Will containers be reused?Will the container be planted with the seedling, re-quiring it to be biodegradable? Will seedlings bemachine-planted or hand-planted? Must seedlings becarried to planting sites far from roads? Which con-

83

Figure 1.5l.--Shape/size pot considerations determine amount of medium needed, affect root growth anddevelopment, and dictate bench or ground space needed for lining-out. Volume of individualplastic bags (Al is *22 percent less than that ofPoly-pot containers (B) having same height andwidth; yet geometrical design of both types allows a given bench area or transport box to holdequal numbers of each container.

8 4

Figure 15-2.-Cuuities in the Todd Planter Flats have block cells that are tapered rather than havingthe same diameter at top and bottom. Taper severity influences calculation of pottingmedium needed, plug extraction at lifting, and root contact with soil when seedlingsare outplanted.

Figure 15-3.-Leach Cone-tainer individual cell units of 10.2,15.2,and 24.8 cm in length. Alt have internal ribs, run-ning the length ofeach cell, which prevent root spiral-ing.

85

Figure 15-4.-Top view (A) of Styroblock containers, showing large and small diameter cavities. Bottom view(B) shows root egress/drain vents and “runners” that keep the block off the ground to allowair-pruning of roots.

86

&her type utilizes available nursery space most effi-ciently?

These are important questions because containertype affects the entire production operation, includingthe degree of mechanization possible. For example,processing of plastic bags, including filling, sowing,covering seeds, and transporting to the field (fig. 1511, cannot be as highly mechanized as processing ofStyroblocks (fig. 15-4).

Several lists of container product manufacturershave been published (I, 22, 25). Unfortunately, listsare quickly outdated as new product lines are addedand old ones are eliminated. Some manufacturers andtheir products are listed in Appendix 15.

15.1.5 Container Systems: Some Historical Per-spectiues. -Ornamental and vegetable nurserieshave used mechanized seedling production techniquesfor over 100 years (5). But only in the last 15 to 20years has enough interest developed to use highlymechanized sytems for forest seedling production.

Interest came from decisions to reforest marginal,drier, cutover lands in North America and Europe. Onsuch lands, survival rates of container-grown stockare greater than those of bare-root stock. Simulta-neously, because affected countries have high laborcosts, research began on mechanized techniques tolower production costs. Today, containerized stockreaches correct size for field planting in a muchshorter time than does bare-root stock, and large-scale mechanized container systems for pine may becompetitive with bare-root operations (II).

In the tropics, abundant, cheap labor has restricteddevelopment of mechanized container systems. In thelast decade, however, two events caused a reevalua-tion of containerized systems for tropical areas wherelocal pot materials are available (8, 14,15): high de-mand for bagged pine seedlings (Surinam, Venezuela,and Brazil) and more demand for hardwood seedlingsplanted in dry areas for agroforestry and fuelwoodprojects (Haiti and Brazil). One of the most successfuloperations was that of CONARE (Compaiiia Nationalde Reforestation) and CVG (Corporation VenezolanaGuyana) in Venezuela in which 100,000 ha were ma-chine-planted with containerized pine (in plasticbags) between 1972 and 1979 (3).

Diverse handmade container types commonly usedinclude clay balls, split bamboo pots, plastic bags, claypots, tarpaper pots, tin cans, and milk cartons. In gen-eral, nonrigid containers such as plastic bags(fig. 15-l) are filled individually by hand; rigid con-tainers such as tarpaper pots and tin cans are lined-out upright and filled by shoveling sieved, loose soilover them. One disadvantage of the latter method isthat soil packs between containers and serves as amedium for weed growth. Another problem with con-tainers is that, if roots egress and grow into soil underthem, the root system must be pruned or much of it is

lost by stripping when pots are lifted. Some speciesare not suited for container production (9 1 .

15.1.6 Major Container Systems of the 1970’s and1980’s. -Container types and systems are discussedfrom different approaches. One approach lists threetypes: tubes, plugs, and blocks (I). Another lists twobroad types and several divisions within each type(221, as follows:

A. Containers planted with seedlings:Al-those filled with rooting medium: open mesh

plastic tubes, and several paperpot systems(e.g., Conwed open mesh tubes, Walters’square bullets, and Alberta peat sausage).

A2-those not filled with rooting medium:molded blocks of peat, woodpulp, or plasticfoam and fiber (e.g., Polyloam, Tree Start,and BR-8 Blocks).

Both Al and A2 are respectively equivalent to thetubes and blocks of Barnett and McGilvray (11. ButWalters’ bullets are square, not round, and should notbe confused with solid cells.

B. Containers not planted with seedlings:Bl-cells are individual units that can be uni-

tized in trays or racks for easier handling;cells and racks are usually made ofpolyethylene (e.g., Leach Cone-tainer; fig.15-5);

B2--blocks are units of separate cavities or cellsthat are permanently attached to each other;

Figure 15-5.--Polyethylene multipot tube containers that are uni-t i zed in ra ised t rays or racks . Cel l s wi th cul lseedlings or non-germinants ure easily replaced withfull cells.

87

materials are high density polyethylenemultipots and expanded bead polystyrene(e.g., Styroblock and Todd Planter Flats;figs. 15-2 and 15-4);

B3-books are units of cavities in rows formedfrom thin polystyrene sheet plastic; sheetshave hinges and open like books (Spencer-Lemaire Rootrainer; fig. 15-6) or come intwo pieces that snap together (Tubepak).

Cell and block/book designs correspond to Barnettand McGilvray’s tubes and plugs respectively;“Speedlings” are really Todd Planter Flats, made bySpeedling Inc. Book designs are also called“Rootrainers”, because internal ribs direct rootgrowth downwards.

Five container systems particularly adaptable totropical areas are discussed in Appendix 15: Rootrain-ers, rigid polyethylene tubes, paperpots, Styroblocks,and Poly-pots. Some types are highly desirable be-cause they are reusable.

15.2 Selecting Growing Medium

15.2.1 Ideal Medium Properties. -A suitablegrowth medium provides anchorage, nutrients, andmoisture for growing seedlings (Chap. 9). Mechanizedcontainer operations also require that a growthmedium be light, be easily handled, maintain con-stant volume when wet or dry, be free of pests, be

readily stored for long periods without change inphysical and chemical properties, and be easilyblended into reproducible materials. Sand and soil areexcluded because of their weight limitations. Proper-ties of several “soil less” products having these specialqualities are briefly discussed below; more detaileddescriptions are given by others (5,X!, 23 ).

15.2.1 .I Peat. -Sphagnum peat is the basic compo-nent of pot medium used in growing containerizedseedlings for forestry, horticultural, and agriculturalpurposes (5). It is also used for root cuttings (18) andair-layering vegetative propagation techniques (6).Managers are cautioned that “peat moss” is a catchallfor many separate components, including naturalsedge peat, peat humus types, and many commer-cially available mixes. Of these, sphagnum peat hasthe best physical and chemical properties.

Sphagnum moss, on the other hand, consists of un-decomposed materials and is not suitable for con-tainerized growth medium. All peats are mineralpoor, requiring fertilizer to maintain seedling growth;acidity should be in the pH value range of 4.5 to 6.0.Because the mineral and acidity status of peats arevariable, caution must be used when purchasing themso that the delivered peat actually has the pH valueand nutrient levels advertised. For container mixes,up to 75-percent is used; 50-percent peat is usuallyadequate. Other components mixed with peat are ver-miculite and perlite.

Figure 15-6.-The Spencer-Lemaire Rootrainer (book planter) can be opened any time without dis-turbing the seedling to check for root development or to remove plugs for outplanting.When closed, internal ribs keep roots from spiraling. Containers are easily unitized inraised trays. If seedlings must be repacked before transporting and outplanting, thiscontainer is one of the easiest to use.

8 8

Cost is the biggest drawback to using peat, particu-larly when it is shipped overseas. Yet, when seedlingsmust be carried to remote planting sites, when nosuitable local substitute for peat exists, and whenfunds are available, the advantages of peat exceedcost disadvantages. Peat moss costs are crucial whendeciding ideal container volumes for species to beplanted (i.e., the greater the volume filled, the morepeat used and subsequent higher costs).

Table 15-l.-Chemical composition of filter-press cake residue ofsugarcane’

ConstituentComposition on a dry weight basis

Average Range of values------------Percent ___________

15.2.1.2 Vermiculite. -Vermiculite is a bulkingagent in pot mixes that keeps the growing mediumfrom settling and compacting and maintains good aer-ation and drainage. It is a light, expandable, plate-like 2:l silicate mineral. After mining, vermiculite isrun through high temperature (1,OOOW furnacesthat force bound water out and plate layers apart.This process forms sterile, porous, sponge-like kernelsthat moisten and dry readily. Kernels are graded intovarious sizes, from horticultural grade No. 1 (5 to 8mm) to No. 4 (0.75 to 1 mm). Products termed “atticfill” and “poultry/kitty” litter are cheaper versions ofgrade No. 1; “block-fill”, however, is water-repellenttreated and should not be used. Coarse sizes are bestfor large containers and finer sizes for seed germina-tion trays and small volume containers.

Nitrogen (N) 2.19Phosphorus (PsOs) 2.77Potassium (KeO) .44Calcium (CaO) 3.05Magnesium (MgO) .49Manganese (MnOe).24Iron (FezOs) 1.05Boron (BaOe) .OlOrganic matter 39.50Loss on ignition 42.20Sucrose 3.00Moisture (fresh) 61.00Moisture (stored) 15.00Volume weight2 .375

*Source: (19).2Calculated on a dry-weighted basis.

‘1.07-3.131.34-6.30

.02-1.77

.98-6.24

.42-.58.17 .lO-

.26-4.71

.oo-.02. . . . . . . . . . . . . .. . . . . . . . . . . . .

2.00-4.0059-69

9-47.372-.378

Other advantages of vermiculite are:. neutral reaction and high buffer capacity;. high water retention capacity unless compacted(squeezed) when moist;

plants. Except for the lower K content, the fertilizervalue of filter-press cake may be as great as that ofanimal manures. Its main advantages are cheapness,slow release of nutrients, minor-element content,high bulk and high water holding capacity, high ex-change capacity, and mulching properties.

. high cation exchange capacity; and

. enough natural Mg and’K to supply most plants.15.2.1.3 Perlite. -Perlite is another light, usually

granular bulking agent made by heating crushedlava. The resulting sponge-like, sterile granules hold3 to 4 times their weight in water and have a pH valueof 6.0 to 8.0; particle sizes are 1 to 3 mm. Unlikevermiculite, perlite lacks buffering capacity, cationexchange, and mineral nutrients. Its usefulness is toincrease aeration and moisture retention in potmixes.

Filter-press cake is an attractive lightweight sub-stitute for peat. A major disadvantage is its high pHvalue, which ranges from 8 to 10. Obviously, thisvalue must be lowered to about 5.5 if this material isto be used for growing pine seedlings. This can be doneby composting filter-press cake with animal manures,then treating it with an acidic fertilizer that lowerspH value and supplies N (table 13-9).

15.2.1.4 Sugar-cane Waste. -Another lightweightmaterial with potential for pot mixes is the filter-press cake that remains after refining sugarcane. Thematerial is abundant and relatively cheap in manytropical areas. Some of its physical and chemical prop-erties have been studied (table 15-l).

15.2.1.5 Rice Hulls.-An excellent substitute forvermiculite is rice hulls. They are lightweight, havehigh bulk, hold moisture well, and are easily obtainedin rice-producing countries. Depending on processingstandards, grinding may be needed to increaseflowability of rice hulls in mixing and filling opera-tions. Rice hulls can be used in composts and as agermination medium in seed trays.

The following data and recommendations are takenfrom a report on filter-press cake by Samuels andLandrau (19): It easily absorbs moisture when dryand its volume-weight ratio is low. Of the major plantnutrients, filter-press cake is highest in P and PzOs; Ncontent is somewhat lower. The K content is low andaverages 0.44 percent as Kz, with a range of 0.02 to1.77 percent; the higher figure is extremely rare.

15.2.1.6 Compost.-Compost is a useful pottingmedium ingredient if the composting process isclosely controlled. Potentially desirable traits of com-post are:. low weight, depending on major components used;. low shrinkage;. good moisture retention;. inexpensive once local sources of raw materials are

identified;Calcium content is high, averaging about 3 percent . high fertility if properly prepared;

as CaO. Magnesium and minor elements such as Mn, . easily shredded and screened to uniform size;Fe, and B are present in sufficient amounts for use by . mixes well with sand, perlite, and vermiculite; and

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4 does not immobilize nitrogen or other nutrients.Major criteria for judging compost are how well it

provides good aeration, maintains acidity, and re-duces unit seedling weight in containers. Fertilizeramendments provide elements that are missing or inshort supply in the compost. Potential problems inmaking compost are:. obtaining a steady source of homogeneous, raw com-

post materials (rice hulls, horse manure, cow ma-nure, etc. );

Table 15-2.-Procedures for determining total porosity, aerationporosity, and water retention porosity of containermedia’

Materials Procedures

Container withdrain hole at bot-tom, plug for drainhole in container,and graduatedcylinder or otherdevice for measur-ing water volume.

1. Plug drain hole and till containerwith water; measure volume ofwater in container (= containervolume).

. making compost in time so that material is readyfor the beginning of production runs;

. obtaining an end product that is free of pests and

2. Empty container and fill with soilmix; slowly and thoroughly satu-rate mix by adding water at oneedge of container and keepingtrack of water added (= total porevolume).

disease organisms; and. avoiding C:N ratios that are too high (~3O:l) in

finished compost material.

3. Unplug drain and catch water thatruns out; measure volume ofwater drained (= aeration porevoluqe).

Appendix 13 outlines procedures to produce com-post of desirable physical, biological, and chemicalcomposition (16).

4. Porosity is obtained by dividingpore volume (step 2) by containervolume (step 1).

15.2.1.7 Wood Products. -Sawdust, wood shav-ings, and ground bark can be used in place of sphagumpeat in pot mixtures. Sawdust and bark are not usedexclusively but are mixed with other materials. Agedor composted wood products are best because freshmaterials have high C:N ratios, r150:l (22 ), that im-mobilize N and make young seedlings chlorotic. Somefresh barks have chemicals that are toxic to plants.

5. Aeration porosity is obtained by di-viding aeration pore volume(step 3) by container volume(step 1).

6. Water retention porosity is obtainedby subtracting aeration porosity(step 5) from porosity (step 4).

In Summary:

Advantages of wood products in pot mixes includelightness and ease of handling when ground, moder-ate cation exchange, and small but significantamounts of all major and minor elements. When costis not a limiting factor, sphagum peat is still preferredbecause it has higher cation exchange, better C:N bal-ance, and fewer problems with harmful organismsand toxic substances.

Porosity (%) = contamer mix pore volume x 1O6.container volume

Aeration porosity (%) aeration pore volume x loo.= container volume

Water-retentionporosity (o/o) = porosity - aeration porosity.

Qource: (21).

15.2.2 Optimum Growth Medium

15.2.2.1 Porosity and Aeration Considerationc- mizes weight and facilitates container handling inThe “optimum” growing medium for a given situation most mechanized operations. Other mixtures used aredepends on several factors, including requirements of 3:2 and 3:l ratios of the same components (22 1. Somethe species grown, container volume, and available nurseries successfully use peat without vermiculite orpot mix (12 ). Seedlings do better in moist rather than perlite. Examples of homemade medium are 2:l:ldry or wet media. Shallow containers with fine tex- mixtures of bagasse (sugar-pressed cane fibers), ricetured materials have better moisture retention but hulls, and alluvial soil in Haiti (20 ); 2: 1 alluvial soil,poorer aeration than deep containers with coarse tex- filter-press cake mixtures at the Monterrey nurserytured materials because of less medium porosity. in Puerto Rico; 1:4 and 2:3 ratios of topsoil and sandPorosity determines the space available for water, air, and 2:3 ratios of rotted cow manure and builders sandand root growth. Large pores aid aeration, whereas (13 ); and a 4:3 mixture of sand with well sieved com-small to fine pores aid water retention; thus, both are post (7). Most tropical countries do not use “soil less”important. medium.

Spomer (21) developed a simple procedure for deter-mining container porosity, aeration porosity, andwater-retention porosity (table 15-2). Generally, aera-tion porosity values ~10 percent are considered low;values >25 percent are considered high.

15.2.2.2 Examples of Mix Proportions.-A 1:l mixof shredded sphagnum peat and vermiculite mini-

The proportions of medium component affectseedling growth by changing porosity and drainage.Adding more vermiculite or perlite to peat increasesaeration and drainage (4). But too much vermiculiteallows pot mix to fall through drainage holes, whichcan cause seedling plugs to fall apart when they areremoved from containers. Areas of constant humidity

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and high rainfall require better drained (coarser)mixes, whereas dry areas need finer medium withmore moisture retention.

15.2.2.3 Synthetic Mixes. -Commercial pot mixesoffer advantages to some nursery managers, Exam-ples are Jiffy-mix, Pro-mix, and Redi Earth. All comepre-mixed to be placed directly into containers. Mostare sterile and have pre-added nutrients. Disadvan-tages are their high cost, no control over componentsin the mix, unneeded or nonbeneficial nutrients, andless than ideal aeration and drainage. Buying con-tainers prefilled with synthetic mix may be cost effec-tive when seedlings are needed in the shortest timepossible, as in erosion control and landslide stabiliza-tion. Appendix 15 lists commercial suppliers of potmixes and their addresses.

15.3 Basic Equipment

The right equipment is essential for mechanizedcontainer systems. Design and parts may vary bycountry, but the functions of basic pieces are thesame. Equipment used at the ITF nursery in the late1970’s to produce pine seedlings in Styroblocks (26) isdiscussed below. Gravity feed systems complimentmachines whenever possible in all operations (see Ap-pendix 151.

25.3.2 Compost Shredders. -Shredders (fig. 15-7)process agricultural byproducts such as filter-presscake, coffee chaff, rice hulls, coconut hulls, straw, etc.,before they are composted. Shredding forms smallparticles, increasing surface area for more rapid de-composition. After composting, a final shreddingbreaks up remaining clumps; improves filling and set-tling of medium into small cavities; and allows bettermixing with perlite, vermiculite, and other mediumcomponents.

Shredders are integrated into production opera-tions in two ways. In one method, equipment is set ona level area. Shredded material falls onto a mechani-cal conveyor, is transported to a large mixer, and isuniformly mixed with other components before beingtransported to a filling hopper.

In the second method, shredders are in the upperlevel of a split-level building; gravity then feedsshredded material into a mixing hopper on the firstlevel (Appendix 15), thus eliminating the need for aconveyor belt.

Shredders come in various sizes. Those with thecapacity for grinding about 7.5 m3 of material perhour are adequate for nurseries producing ‘I 1 millionseedlings per year. Electric models are less noisy thangasoline powered shredders. Either types must behighly mobile and relatively trouble-free in opera-tion. Raw shredded material, ranging from 0.2 to 0.5cm long, should be screened so that the final product(3 to 6 mm) is homgeneous.

; ./

Figure 15-7.-A small, very mobile, gas-powered compost shreddercapable of processing 7 m3 per hour of rice hulls,sugarcane waste, straw, and other materials.

15.3.2 Soil and Compost Sievers.-Unsieved potmedium can cause poor aeration and poor drainage.Final medium should have a consistency that mini-mizes silting and that has sufficient large-size parti-cles. Up to 50 percent of the pot medium should fallthrough 1.4- to 2.4-mm sieve openings. Very finesand, perlite, vermiculite, and expanded polystyrenebeads are excellent lightweight materials that in-crease bulk and improve drainage, porosity, and aera-tion.

Mechanical sievers can sieve 3 to 5 m3 of materialper hour. Hand sieving is done if machines are notavailable. Ideally, a mechanical siever is placed be-tween the shedder or soil mixer and the mixing tank.

15.3.3 Medium Mixer.-Concrete mixers or somesimilar machine (fig. 15-8) should have a 3 to 10 m3capacity. Medium ingredients enter by gravity feed orby conveyor belt. The mix is wetted to improveflowability; the material is moist to the touch, butexcess water cannot be squeezed out with the fingers(Sec. 15.4.2). After mixing, the final medium is trans-ported to a filling hopper.

25.3.4 Potting Machine. -Vibrating plate-typemachines are capable of filling a tray with containers

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Figure 15-8.-A small electric mixer capable of processing 3 to 10m3 of potting material per hour.

in 20 seconds. A single machine can fill 80,000 to300,000 cavities per each manday of work, dependingon cavity volume, kind of pot medium used, and con-tainer types (e.g., rigid types being easier to fill thanflexible or assembled types). For less mechanized op-erations, one worker can take medium from the fillinghopper and fill containers by hand or by gravity feed(fig. 15-9). After fl ta s are filled, they are sent by con-veyor belt to the semi-automatic seeder.

15.3.5 Semi-Automatic Seeder. -Before seeding,compactors push pot media down about 1 cm, creatingspace for seeds (fig. 15-10). Vacuum controlled seedersfit exactly over cavities of multiple cavity flats (fig.15-11). After aligning the plate with seeds over thecontainers, vacuum is cut and the seeds fall into thecavities. One operator can easily seed 100,000 cavitiesin an g-hour day.

A hand-operated seeder can be made of plexiglass tofit any cavity configuration. It has two sliding plateswith matching holes, the bottom plate having aslightly larger diameter hole than the top plate. Whenthe holes are unaligned, each hole is filled with seeds.Sliding the top sideways allows the seeds to fall

straight through the bottom plate into underlyingcavities. Commercially made seeders can be pur-chased to desired specifications.

15.3.6 Final Filler.-Machine or hand spreadersplace a small amount of vermiculite or other gritcover over seeded cavities as they pass under a hopper(fig. 15-12). Excess covering of seeds will lower germi-nation. After applying the filler, mist watering keepsit from blowing away. A final filler is not needed intightly enclosed, high-humidity germination houses.

15.3.7 Forklift and Wagon.-Seeded flats arestacked manually on pallets, loaded by forklift ontowagons, driven to seedbeds, and lined-out (fig. 15-13).Lining-out is a potential bottleneck because workersneed considerable space for maneuvering a forkliftand accommodating the flats. Lift operators must beskilled to avoid spilling loaded trays and damagingflats. Pallets can serve as permanent bench tops.

15.4 Other Operational Techniques

Other operations are essential to produce healthy,vigorous seedlings. We review these operations below,giving alternatives whenever possible and their po-tential problems,

15.4.1 Medium and Facility Sterilization. -Potmixes with peat, vermiculite, and perlite as majorcomponents do not ordinarily require sterilization.Mixes with ground bark, sawdust, compost, and soilshould be sterilized. In research trials, all mix treat-ments, including the control, are sterilized (excepttrials on the effects of sterilization treatments).

Steam heat sterilization is preferred for “soil less”mixes. Chemical fumigants can bond to vermiculiteand finely ground peat and compost, being toxic toplant roots even after treated material is aerated. Iffumigants are used, mixes should be moist, but notwet; fumes dissipate in 2 days to 2 weeks, dependingon the product used. Steam heating at 82°C for 30minutes effectively kills most pathogenic pests andweed seeds. Since steam heating is used extensivelyfor horticultural and vegetable crops, a wide range ofsterilization equipment is available. Dry-heat steril-ization can alter soil chemical properties (17).

Medium mixing and filling areas, plus the equip-ment involved, should be kept clean and free of weedseeds and other contaminants. Disinfecting alterna-tives are washing with solutions of commercial bleach(50-percent sodium hypochlorite) diluted 1O:l withwater, boiling water, rubbing alcohol, and live steamG?Z). Flats, tools, and nursery walls and floors shouldbe disinfected before each production run.

15.4.2 Filling Container Cauities. -Slightly moistmedium flows better through the potting machine anddoes not fall out of root egress holes as does drymedium. Water is added to all components when theyare mixed. Peat and other finely ground materials do

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Figure 15-9.-A semi-automatic potting operation in which a worker hand-fills containers passingunderneath the medium hopper on a conveyor belt.

Figure 15-10.-A hand operated mix compactor that presses downpot medium. Hand-operated plate seeders functionthe same way.

Figure 15-11.-A vacuum controlled mechanical seeder that fills allcontainer cavities simultaneously as Styroblockspass underneath on conveyor belt.

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Figure 15-12.~Mechanical final-fillers drop a thin layer of vermi-culite or other grit over seeds in Styroblocks to con-serve moisture around seeds and protect againstbirds.

not wet well when dry because of their nonwettability(hydrophobicity) properties. Commercial wettingagents improve moisture uptake, but chemicals inthem can lower the percentage of seed germination(22). Once pot mix is damp, it must be used beforedrying out.

Motion of the potting machine helps fill containerswhen pot mix is damp. Operators must not force extramedium into cavities with their fingers. A flat-handlebrush smooths away any excess, which is eventuallyused.

25.4.3 Sowing.-Germination percentage of seedlots determines sowing rate. If germination is low,more seeds are sown per cavity, increasing the proba-bility that each has at least one germinated seed. Ifgermination percentage is high or seeds are scarce,then only one seed is sown per cavity.

If seeders pick up and drop only one seed per cavity,the entire operation is,repeated 2 or 3 times. Auto-mated seeders are faster than hand seeders but aresubject to more mechanical problems. When auto-mated seeders break down, hand sowing gets the job

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done (Sec. 9.1.5.2). After sowing, containers aresprayed with a fine mist to moisten seeds before goingto the final filler.

15.4.4 Lining-Out and Germinating

15.4.4.1 Stacked Method.-Stacked containers in agermination house save outside bench space and re-duce seed loss to birds and mice (fig. 15-14). Themethod is only suitable for species, including P. carib-aea, that germinate uniformly in short periods andgrow well in low light conditions. One drawback tothe method is the need for placing wooden “stickers”between Styroblocks. They create space betweenblock layers to prevent fast growing early germinantsfrom bending over block tops. Seedlings straighten upif they have not been bent over too long, but mishan-dling blocks in lining-out will sever seedling tops thatare bent over block edges.

Blocks stacked in criss-cross fashion cannot bewatered. Thus, germination houses are used only forspecies having fast, uniform germination that is com-pleted within 7 to 10 days in a high-humidity environ-ment.

15.4.4.2 Lined-Out Method.-This method in-volves placing seeded containers directly on outsidebenches (fig. 15-13). Placing flats under about 30-per-cent Saran shade for up to 21 days prevents loss frompests. Elevated shade is better than clear or dark plas-tic sheeting placed over containers. In the tropics, thelatter practice can cause extremely high tempera-tures under the sheet that are lethal to germinatingseedlings. Frequent and careful watering will keepmedium and seedlings moist but not too wet; over-watering favors damping-off.

To reduce overtopping of border by interiorseedlings, Styroblocks should be placed in long, nar-row rows about 10 blocks wide. If peat or other steril-ized pot medium is used, weed growth is minimal inexposed cavities. A wide walkway (76 cm) betweenrows can be narrowed to a small path (38 cm), whichis adequate for inspecting seedling stock for pests andgeneral growth performance. Narrow walkways leavemore space for containers per unit of nursery area.

15.4.5 Thinning, Transplanting, and Grading. -Early germinants remain in the original container.From the 7th to 13th day after germination, smallexcess seedlings in each cavity are lifted and trans-planted into empty Styroblocks. After the 14th day,small excess seedlings are removed and discarded.Small, less vigorous seedlings are not transplantedbecause they perform more poorly than do early ger-minants (24 1.

Long lateral roots on thinned seedlings should becarefully clipped rather than removed; this procedureavoids disrupting the growing medium aroundseedlings left in each cavity. Transplant holes shouldnot be closed over J-roots (Sec. 10.1.1.2).

Figure 15-13.--h large operations, forklift tractors are handy for lining-out seeded Styroblocks forgerminating in the open air.

Figure 1514.-Cerminuting seeded Styroblock,s by the stacked method inside an enclosed germination house.

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These thinning and transplanting techniques sepa-rate germinants into three classes: early, more vigor-ous germinants that are left in original containersand lined-out in one sector of the nursery; later, ex-cess germinants that are transplanted into separateStyroblocks; and late germinants that are culled.Sometimes, late germinants are kept if germination ispoor or if seeds are scarce. The result is seedlingsgraded according to date of germination.

15.4.6 Later Tending Care

15.4.6.1 Moisture and Fertilizers. -The moistureand fertilizer needs of seedlings are different for ger-mination, juvenile, exponential, bud development,and stem lignification growth phases (22). Specificguides will depend on the containers used and speciesgrown. Some general guides and suggestions aregiven in this section. For container operations, fixedirrigation systems are used more than mobile ones.Systems producing small and medium droplets (mist,semi-mist, and fine spray-nozzle types) are betterthan those producing large droplets. Smaller dropletsdo not damage young seedlings or wash out pot mix.

Persistent drip of fixed systems may wash outseedlings or medium from containers. Alternatives toprevent this are supplying water from beneath (2 ) oralongside benches (i.e., not from overhead), drawingwater from the top of overhead pipes, draining outexcess water after each use, and running a line downfrom the nozzle to the bench surface between contain-ers (22). Large spray-nozzle and impulse-type sys-tems are more adapted to irrigation of bare-root nurs-ery beds.

Combining slow-release fertilizers with pot mix ortop dressing fertilizers on container surfaces (10) isnot usually done in mechanized container operationsbecause:. soluble fertilizer pellets or granules are readily

leached from the pot mix;. when seedling growth stages change, certain nutri-

ents must be added or reduced; if they are alreadyin the mix, controlled additions or reductions areimpossible;

. pellet and granule dissolution are uncontrollable;thus, specific nutrients are not always providedwhen needed most; and

. slow dissolving fertilizers often tend to raisemedium pH value and salt content; lowering bothrequires flushing with excess irrigation water.

For containerized systems, nutrients are usuallyapplied through the irrigation system. Fertilizer for-mulation, concentration, and application frequencyare easily controlled. The general scenario of wateringand fertilizing for different seedling growth stages is:

1. Germination stage-frequent but controlledwaterings to keep medium moist but notwet; no nutrients are added that provide

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“rich” materials for damping-off or otherpathogenic organisms.

2. Juvenile stage-less frequent irrigation thatallows the growth medium surface to drybetween waterings; high P and K andlower-level N fertilizers are added to max-imize early growth; a final rinse of foliagewith plain water is needed to avoid possi-bility of salt burn and alga growth.

3. Exponential growth-reduce watering; bal-anced N-P-K fertilizers are added;seedling growth rates (too fast or too slow)are closely monitored to anticipate changeto next water and fertilizer regime orother corrective action such as top-pruning.

4. Bud development or stem hardening-whenseedlings reach desirable height and arepurposely drought stressed (hardened);this process is done by heavy watering toremove N and then subsequent drying ofseedlings almost to the wilting point; theyare rewatered to stop wilting and then in-frequently rewatered with low N and highP and K fertilizers to facilitate hardening.

Other nutrients are added according to the needsshown by periodic foliage testing (Chap. 13). Unex-pected micronutrient deficiencies are usually cor-rected by applying foliage sprays rather than solidmaterials.

15.4.6.2 Protection and Pest Control. -The guidesdiscussed in Chapters 12 and 16 can be followed. Ingeneral, reduced exposed area and use of uncontami-nated pot medium reduce weed growth more in con-tainer than in bare-root nurseries. Consequently,weeding is minimal and confined to borders ofbenches and is controlled by hand or by chemicals.Judicious use of asphalt, cement, turf, and gravel forroads and walkways will reduce weeding.

Having a cat or two around germination houses,potting sheds, and outside benches is an effective con-trol against mice, rats, and birds. Pathogen buildup isavoided by composting or burning thinned, cull, andother seedling materials. Otherwise, looking con-stantly for problems and using approved pesticidesshould keep most pests in check.

15.4.6.3 Znoculation with Mycorrhizal Fungi. -Forlarge potting operations, collected mineral soil andduff with inoculum is kept fresh for long periods bystoring in burlap sacks lined with plastic or in binslined and covered with plastic sheeting. When potcomponents are mixed, inoculum is added 2 to 3 per-cent by volume. Adding inoculum this way has risksthat are minimized by collecting inoculum fromhealthy plantations and by careful monitoring fordamping-off, root rot, and other problems as inocu-lated seedlings develop.

15.4.6.4 RootlShoot Growth Control. -Mechanicalroot pruning is not possible for containerized stock.Root growth is controlled by the shape-volume-design

characteristics of containers used (Sec. 15.1). Sinceroot volume is finite, estimating outplanting datesmust be accurate because long-term holding ofseedlings is impossible. If seedling top growth hasbeen excessive in relation to root growth, tops may beclipped back. This procedure stops top development,encourages more root development, and produces bet-ter shoot/root ratios (see Chap. 11).

Using wide rows minimizes border or edge effectaround containers and reduces overtopping of interiorby border seedlings. Effective windbreaks and prop-erly maintained irrigation systems reduce water andnutrient drift from bench edges, giving edge and inte-rior seedlings the same moisture and fertilizerdosages.

Experience at the ITF Nursery showed that benchcolor and container placement affected seedlinggrowth. When concrete benches were new and highlyreflective, seedling mortality was sometimes greatnear bench edges when containers were set far to theinside (i.e., expqsed to the reflective bench surface).Apparently, localized heating or higher evapotranspi-ration was responsible (fig. 15-15). Alternative solu-tions are using less-reflective surfaces, such as woodor screens, over elevated pipes (fig. 2-2B); paintingnew benches with less-reflective paint; and position-ing containers so they extend over bench edges.

15.4.7 Lifting, Packing, and Transporting. -Inthe tropics, delivering containers directly to the fieldfor outplanting is preferred. The lifting and repackingprocedure (fig. 15-16) is not recommended because itis time and labor consuming, can cause severe rootdamage, and augments transplanting shock. Local

Figure 15-15.~Mortality of pine seedlings at edges of Styroblocksmay have been caused by localized heating and/orhigher evapotranspimtion on raised cement benches.

Figure 15-16.-Food packaging techniques using plastic wrap are easily adapted for transportingcontainerized stock.

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situations can override these factors. Examples are asource of cheap and plentiful labor, a mandate to em-ploy that labor, a need to reuse containers, a lack oftransport vehicles, and an inability of planting crewsto cull effectively in the field.

Single cells and book planters are highly adaptivefor repacking (fig. 15-16); block systems are less sobecause of plug extraction difficulties. Completedrenching of containers 2 to 3 days before lifting,without subsequent rewatering, aids lifting. Foodwrapping paper and wax-lined cardboard boxes arereadily adapted to repacking and transporting forestseedlings. From lifting until planting, seedling pro-tection from sun and wind is essential.

Outplanting success is highest when seedlings areplanted quickly. Lifted and repacked seedlings aremore susceptible to drying than seedlings left in theiroriginal containers. But seedlings transported in orig-inal containers damage easily if they are moved toand then held at field sites where watering and pro-tection are less controlled than at the nursery.

LITERATURE CITED

1. Barnett, James P.; McGilvray, John M. Con-tainer planting systems for the South. Res.Pap. SO-167. New Orleans, LA: U.S. Depart-ment of Agriculture, Forest Service, South-ern Forest Experiment Station; 1981. 19 p.

2. Belanger, R. P.; Briscoe, C. B. Effects of irrigatingtree seedlings with a nutrient solution.Caribbean Forester. 61(l): 51-53; 1963.

3. CONARE. (Compania National de Reforesta-cion). Algunas consideraciones de politicaforestal relativas a las plantaciones fore-stales y bosques de production. VenezuelaForestal. 6: 12-37; 1982.

4. Davey, C. B. Pine nursery establishment and op-erations in the American tropics. CAMCOREBull. on Tropical Forestry 1. Raleigh, NC:Central America and Mexico Resources Co-operative (CAMCORE); 1984. 36 p.

5. Davidson, H.; Mecklenburg, R. Nursery manage-ment administration and culture. EnglewoodCliffs, NJ: Prentice-Hall. 1981. 450 p.

6. Dorman, Keith W. The genetics and breeding ofSouthern pines. Agric. Handb. 471. Washing-ton, DC: U.S. Department of Agriculture,Forest Service; 1976. 407 p.

7. Fishwick, R. W. Irrigated nursery practice in-struction. Kaduna, Northern Nigeria: Min-istry of Animal and Forest Resources; 1966.19 p.

8. Galloway, Glenn; Gumersindo, Borgo. Manual deviveros forestales en la Sierra Pervana.Proyecto FAO/Holanda/INFOR. Lima, Peru:Ministerio de Agricultura, Instituto Na-

cional Forestal de Fauna y Organization delas Naciones Unidas para la Agricultura y laAlimentacion; 1983. 123 p.

9. Garcia H., Miguel, H. Nursery trials in the con-cession, Bajo Calima, during 1975-1976.Forestry Research Report 22. Cali, Colombia:Carton de Colombia, S.A.; 1977. 4 p.

10. Geary, T. F.; Avila Cortes, G.; Hadley, H. H. Ger-mination and growth of Pinus curibaeu di-rectly sown into containers as influenced byshade, phosphate, and captan. Turrialba. 31:336-342; 197 1.

11. Guldin, Richard W. Regeneration costs usingcontainer-grown southern pine seedlings.Res. Pap. SO-187. New Orleans, LA: U.S. De-partment of Agriculture, Forest Service,Southern Forest Experiment Station; 1983.29 p.

12. Hartman, H. T.; Kester, D. E. Plant propagationprinciples and practices. Englewood Cliffs,NJ: Prentice Hall; 1975. 450 p. 3d ed.

13. Jackson, J. K. Nursery techniques in the savannaregion of Nigeria. Research Paper 32.Ibadan, Federal Republic of Nigeria: FederalDepartment of Forest Research, Ministry ofAgriculture and Natural Resources; 1974. 8P.

14. Ladrach, William E. Nursery tests with new con-tainers for the production of seedlings.Forestry Research Report 17. Cali, Colombia:Carton de Colombia, S. A.; 1977. 12 p.

15. Ladrach, William E.; Gutierrez V., Millan. Com-parison of trees in tubes and bags a year afterplanting. Forestry Research Report 19. Cali,Colombia: Carton de Colombia, S. A.; 1977.9P*

16. Leonard, Dave. Soils, crops & fertilizer use or awhat, how, and why guide. Reprint R8.Washington, DC: Peace Corps, InformationCollection and Exchange; 1980.162 p. 3d ed.

17. Liegel, Leon H. Effect of dry-heat sterilization onchemical properties of Puerto Rican soils.Communications Soil Science Plant Analy-sis. 14(4): 277-286; 1983.

18. Marrero, J. Sphagnum moss as a medium for root-ing pine seedlings. Trop. For. Notes 9. RioPiedras, PR: U.S. Department of Agriculture,Forest Service, Institute of Tropical Forestry,1961; 2 p.

19. Samuels, George; Landrau, Pablo. A filter-presscake as fertilizer. Journal of AgricultureUniversity of Puerto Rico. 39(4): 198-213;1955.

20. Smith, Ron. Personal communication. Supervi-sor. Operation Double Harvest, Nursery Pro-ject. Cazeau, Haiti; 1982.

21. Spomer, L. A. How much total water retentionand aeration porosity in my container mix?

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Illinois State Florist Assoc, Bull, 369: 13-15;1977.

22. Tinus, Richard W.; McDonald, Stephen E. How togrow tree seedlings in containers in green-houses. Gen. Tech. Rep. RM-60. Ft. Collins,CO: U.S. Department of Agriculture, ForestService, Rocky Mountain Forest and RangeExperiment Station; 1979. 256 p,

23. Tinus, Richard W.; Stein, William I.; Balmer,William E., eds. Proceedings, North Ameri-can containerized forest tree seedling sympo-sium; 1974 August; Denver, CO. GreatPlains Agriculture Council Publication 68.Washington, DC: Great Plains AgricultureCouncil; 1975: 458 p.

24. Venator, C. R. The relationship between seedlingheight and date of germination in Pinuscuribaea var. hondurensis. Turrialba. 23(4):473-474; 1973.

25. Venator, C. R. Directory of manufacturers anddistributors of containers suitable for grow-ing forest tree seedlings. Res. Note ITF-15.Rio Piedras, PR: US. Department of Agricul-ture, Forest Service, Institute of TropicalForestry; 1974. 8 p.

26. Venator, C. R.; Rodriguez, A. Using Styroblockcontainers to grow Pinus curibueu var. hon-durensis Barr. & Golf. nursery seedlings.Turrialba. 27(4): 393-396; 1977.

CHAPTER 16

16. MECHANIZED BARE-ROOTPRODUCTION

Advantages and disadvantages of bare-root nurs-eries were discussed in Chapter 9. Because bare-rootseedlings take longer to develop than containerizedseedlings, considerable more lead time is needed forthe production stages shown in figure 5-1. Proceduresdescribed in this chapter are based primarily on oper-ational practices used in large commercial pine nurs-eries in the Southern United States (P. tuedu), Aus-tralia (P. rudiutu), and Eastern Venezuela (P.curibueu). Large scale nurseries are highly special-ized farming operations that use many techniquescommon to cultivating crops. Only generalized proce-dures are discussed because different types of ma-chines and tending practices are used in individualnurseries over several months (10).

16.1 Bed Preparation

16.1.1 Plowing and Disking. -Raised beds usuallyhave less than 0.5 percent slope to minimize erosion;orientation can be east-west for small beds (Chap. 4).Beds are prepared by plowing and disking with trac-tors. A typical bed is 1.2 m wide and up to 200 m long.Virtually all commercial nursery equipment is manu-factured for 1.2-m-wide beds. Since tractor paths areusually 0.6 m wide, only 67 percent of the nursery isactually cultivated.

16.1.1.1 Soil Compaction. -A serious problem innurseries is soil compaction and its effects on seedlingroot growth near tractor paths. Compaction forcesfrom vehicles spread out at a 45” angle from the pointof compaction. Thus, a wide tire running down a 0.6-mlane can cause compaction effects within an entire1.2-m-wide bed. One solution is keeping the sametractor paths throughout the life of a nursery.

16.1.1.2 Deep Plowing and Ripping.-Plow pansare frequently created by a plow and undercutting barpassing through the soil over and over at the samedepth. Pans restrict root growth and impededrainage. Deep plowing occasionally to 30 cm breaksup plow pans, as does “ripping” with a power-mountedripper or vertical blade that reaches a depth of 30 to50 cm.

16.1.2 Fallows and Cover Crops.-Fallow bedsmust be turned over 4 to 6 months before seed sowing;this allows fallow material time to decompose.Seedling and fallow rotation periods should be suchthat bed fertility and organic matter levels are main-tained. Some nurseries utilize a 2:l crop to fallowrotation, i.e., 2 years of beds and 1 year of fallow;others utilize a 2:2 rotation. Legume crops are pre-ferred because of the extra N they fix. Sometimes agrass cash crop is grown on fallow land to increasenursery income.

Many nurseries incorporate cull seedlings back intothe nursery beds. For best results, seedlings arechopped and turned under immediately. This practiceis only suitable for beds that will lie fallow for 1 to 2years or are being prepared for a cover crop. Choppedseedlings take at least 1 year to decompose into usableorganic matter and may harbor disease organisms.

Additional organic matter can be added to beds byspreading sawdust, bark chips, or manure. Manureshould be composted to kill weed seeds before it isspread on the nursery bed. All organic matter shouldbe thoroughly incorporated into nursery beds ahead ofcover crops and be allowed to stabilize. An overlookedaspect of maintaining high organic matter levels inthe nursery is the buffering effect of organic matter onchanges in acidity.

16.1.3 Mounding. -Mounding is done with a plow,which throws soil inward from two sides, forming araised bed about 15 cm high. Beneficial aspects ofmounding are: 1) increased aeration in loose soil,

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which is vital for good root growth; 2) increaseddrainage that reduces that threat of waterloggedsoils; and 3) reduced effects of compaction in the beditself (fig. 16-l).

Immediately trailing the mounding plow, a rollerlevels the mound and forms a flat surface. If nurserybeds are scheduled for fumigation or sterilization, thisis done before mounding.

16.2 Fumigating

When nurseries are highly mechanized, seedlingcrops are extremely valuable. For example, in theSouthern United States, cash value of forestryseedlings may exceed $40,000 per ha. Therefore, man-agers must pay special attention to control of weeds,nematodes, pathogenic fungi, and soil pests. Steamsterilization of soil is the most effective way to controlnursery diseases and pests. But this method is onlypractical for containerized operations, using small tomedium volumes. For bare-root operations, fumigat-ing is just as effective and more practical for largevolumes of soil that must be treated.

16.2.1 Methyl Bromide Procedures. -The mostpopular and effective commercial fumigant for bare-root nursery beds is methyl bromide (table 10-l). Itkills most weed seeds, pathogenic fungi, soil insects,and nematodes. Chloropicrin is usually mixed withmethyl bromide to increase its effectiveness againstsoil insects and to act as a warning agent because ofits odor and tear-gas effect on eyes.

Methyl bromide is highly toxic. Because it is nor-mally applied as a gas mixture, special precautionsare needed to keep the gas in the soil. Gas activity isgreater in warmer climates. Because of the diverseclimates in tropical regions, suitable application ratesmust be obtained from local pesticide officers or pesti-cide distributors in each country.

The normal method of applying gaseous fumigantsis with chisel plows having injection valves attachedto plow prongs (6). The plow brongs can be adjusted toapply gas at precise depths. After the gas is injected,the soil is covered with plastic sheeting ~0.04 mmthick by 3.3 m wide. Injection and covering is a singlemechanized operation for entire fields or on singlestrips. Sheet edges are covered with soil to keep thegas from escaping into the atmosphere and to preventthe sheets from blowing away. Injection depths shouldbe at least 25 cm. Methyl bromide gas diffuses mostreadily in dry, loose sand (large pore) soils. Severalfactors reduce overall effectiveness of fumigants: lowsoil temperature, high soil moisture, high clay (smallpore) soils, and high organic matter.

16.2.2 Other Considerations. -Some promisingsoil sterilization research exists with clearpolyethylene sheeting and solar energy. Apparently,success of solar sterilization depends on consecutive,bright cloudless days to create constant high tempera-ture in covered soils. If effective soil sterilization canbe obtained by solar energy, significant savings canbe expected. Normally, fumigating nursery soils is

Figure 16-1.-A hydraulic tractor-mounted blade being used for undercutting pine seedlings onraised or mounded seedbeds.

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suite expensive, as much as $2,900 per ha. Because ofthis high cost, most managers fumigate only onceevery 2 or 3 years, depending on seedling/fallow rota-tion cycles. In some areas, operational fumigation istoo costly (15).

Soil fumigation reduces or completely eliminatesmycorrhizal fungi populations. Thus, following fumi-gation, one must reinoculate seedbeds with mycor-rhizal fungi spores mixed with soil or sand. New com-mercial equipment can spread a thin strip ofmycorrhizal fungi, cultured in vermiculite, in a fur-row along with drilled seeds. But a competent ma-chine mechanic can build a suitable spreader for afraction of the commercial cost.

16.3 Seed Sowing

16.3.1 Sowing Procedures. -Seed sowing is a sim-ple, fairly precise, machine-controlled operation. Atractor-pulled seed drill is adjusted to deliver so manyseeds per linear meter. Small plows open furrows im-mediately preceding drill knives. Seeds are automati-cally dropped into the furrows, then are immediatelycovered by a trailing roller.

Seeds are planted at desired depths by adjusting thefurrow plow. Periodic checks are needed to assure thatthe drill is not clogged and is delivering seeds into thefurrows. Wrongly assuming that sowing is normalcauses unnecessary replanting and germination de-lays that in turn upset seedling development andscheduled lifting dates. Before they are sown, seedsare sometimes coated with repellents or fungicides(Sec. 16.4.3)

16.3.2 PZanting Densities. -Most nurseries growseedlings at densities of 150 to 300/m2. At a plantingdensity of 300/m2, 1 hectare of seedbeds producesabout 2 million seedlings, assuming that one-third ofthe area is non-growing space for alleys, roads, irriga-tion pipes, etc. Some nurseries use densities of 350/m2or greater. However, as seedbed seedling density in-creases, there is a corresponding increase in cullseedlings. Recently, there has been a general trend toraise seedlings at lower densities of 150 to 200/m2(18). The assumption is that lower planting densitiesgive individual seedlings more growing space andthus better root systems, i.e., higher qualityseedlings.

16.3.3 Mulching. -Immediately after planting, athin mulch is spread over seedbeds. Mulch provides aprotective cover and prevents drilled seed from beingwashed out by rain. Other benefits of mulch are 1)reduced erosion of the seedbed surface until seedlingfoliage covers the beds and 2) conservation of soilmoisture to aid germination and seedling growth.

Mulches must be non-toxic, biodegradable, and re-sistant to water droplet impact. Also, they must notstop egress of germinating stems to the surface and

should not rot or ferment on top of the seedbed. Allmulches must be able to withstand considerable over-head and sideways splash pressure from irrigationsystems, even though they are applied as thin layersover seedbeds. Mulches commonly used are: sawdust;grit or sand; vermiculite; chopped, dead pine needles;shredded newspaper; chopped straw or similar agri-cultural byproducts; chopped pine bark; commercialHydro-mulch; and rice hulls. The latter are inexpen-sive and readily available in rice-producing countries.

Managers often hesitate to use mulches, fearingthey contain noxious weed seeds or pests. They preferfresh materials such as pine bark, pine needles, straw,and sawdust. With proper planning, even compost canbe used as mulch without fear of harboring pests.Compost pits should be started a year or so beforemulch is needed. Compost purity is checked by mak-ing weed germination tests before applying mulch.Properly prepared compost mulch (Appendix 13) willnot induce nutrient deficiencies or chlorosis inseedlings as it decays.

16.4 Tending Seedlings

16.4.1 Herbicides. -Some people dislike herbicideuse in forest nurseries. Alternatives for reducingweeds, complete soil sterilization and hand weeding,have several limitations. Soil sterilization is not al-ways feasible because of costs. Sterilizing or fumigat-ing soils also destroys beneficial microorganisms, in-cluding mycorrhizal fungi. Sterilization can evenalter soil acidity. Hand weeding is effective but expen-sive, particularly for a nursery producing millions ofbare-root seedlings. Poor supervision of workers andletting weeds get too tall would make hand weedingundesirable for commercial bare-root operations(fig. 16-2).

Preemergent and postemergent. herbicides are veryeffective and cheaper than hand weeding. Table A12-3 (Appendix 121 lists some common herbicides used innurseries in the Southern United States andVenezuela. The only requirement is that herbicides benon-tox c to the tree species grown.“r

Some herbicides are toxic for conifers but not forhardwoods, and vice versa. One example is Roundup,which is toxic for P. curibaea seedlings. Some herbi-cides, including Roundup, are extremely toxic to hu-mans and animals. Correct use requires using safetyequipment, minimizing unnecessary drift, and timingapplications in early morning or late afternoon whenwinds are calmest. Goal was particularly effective andnon-toxic to P. caribaea and P. oocurpu seedlings atCONARE nurseries in Venezuela. Up to 30-day cover-age was obtained; 60-day coverage may be possiblewith a Goal-Lasso mixture. When postemergent her-bicides are not available, mineral spirits or keroseneat 2200 liters per ha kills weeds, does not affectconifers or mycorrhizal fungi, but does kill most hard-woods.

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Figure 16-2.-Hand weeding is too labor intensive and dangerous for most large-scale bare-nwtoperations. If weeds are left too long before being pulled, weed and seedling rootsbecome entangled, making it almost impossible to eliminate weeds without also pullingout seedlings. Uprooted seedlings are seldom replanted correctly, causing high andexpensiue mortality.

For most herbicide applications, a tractor is used topull a high pressure pump and tank sprayer having a6-m boom-extension pipe system on either side. Beforespraying, all nozzles and pipes must be clean andopen; cleaning is best done immediately after spray-ing. Improperly cleaned equipment means cloggednozzles and weed-filled beds that are impossible toclean, even by hand (fig. 16-3). Research control plotsnot receiving herbicides should always be installed tocheck herbicide selectivity. To avoid costly mistakes,herbicides are tested on small experimental plots be-fore using them on a commercial scale.

16.4.2 Moisture Considerations

16.4.2.1 Watering Frequency. -Seedlings have dif-ferent water needs and problems at different stages oftheir nursery development (Appendix 16). Whenyoung and succulent, seedlings are watered enough tokeep them growing but not so much that beds erode orget damping-off. Thus, young seedlings are checkedevery day for adequate moisture, particularly atlevels 2 to 10 cm below the surface where water isneeded most. (9)

As seedlings develop, the biggest problem is under-watering. If seedlings are underwatered during peri-ods of normal growth, both overall growth and vigorare seriously affected.’ Generally, sandy bare-rootbeds are well drained and difficult to overwater. Ex-ceptions are natural low spots or areas where com-

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paction and plow pans impede drainage. About3 months before seedlings are lifted and outplanted,water is purposely cut back to start hardening-offprocesses.

16.4.2.2 Irrigation Systems. -Several overhead ir-rigation systems exist: mist, continuous spray, im-pulse, and trickle irrigation (7, 8). Each system hasadvantages and disadvantages, depending on nurserysize, type of water available (well vs. far awaystream), and available pressure head (natural or man-made). Sometimes, water soluble fertilizers can be in-jected into irrigation water; several injector designsare available (Appendix 16).

Cleaning and maintenance are a must for anywater system, particularly when natural or added dis-solved salts are high. Salts corrode pipe and motorfittings and clog openings of small-aperture nozzles.Failure to clean or replace defective nozzles can causehigh mortality in several beds when young seedlingsare either washed out or dried out (fig. 16-4A). Waterfrom loose pipe connections can cause large seedbedareas to wash away (fig. 164B).

Nursery managers must not hesitate to use water,but irrigation water should be considered a supple-ment to rather than a substitute for rainfall. Eachwatering system should deliver up to 55,600 liters ofwater/ha/day. However, even greater capacity isneeded because a large part of irrigation water is lost

Figure 16-3.-(A) Weeds out of control in bare-root pine beds. (B) Weed-filled beds caused by improperlycleaned herbicide spraying equipment.

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Figure 16-4.-(A) Unnecessary seedling mortality occurred when water from non-functioning impulse irriga-tion nozzle washed out seedlings from bare-root pine beds. (B) Just as disastrous and unneces-sary seedling mortality occurred when loose pipe connections went unattended for a long time.

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tn mp-mtim md rmn@ ftxces.9 watering is also nec-essary to flush away salts that accumulate at the soilsurface from evaporation (12 ).

More detailed information on water schedules,overhead watering systems, and nutrient injector sys-tems for overhead irrigation are given in Appendix16.

16.4.3 Repellents and Pesticides

16.4.3.1 Seedcoat Repellents. -Large seeds (e.g.,Pinus sp.) are subject to predation by birds, insects,and mice because of their long germination periodsand shallow sowing depth. Coating or covering seedswith a repellent such as anthraquinone, a bitter-tast-ing chemical, discourages predation. The repellentstays on the seedcoat as seedlings germinate, prevent-ing plucking by birds. Combining a fungicide such asthiram with repellents on the seedcoat simulta-neously lessens the chance of damping-off and repelsanimals.

16.4.3.2 Gene.ral Pesticide Guidelines. -Selectednursery personnel must be trained to detect insectand disease problems before serious seedling damageoccurs. Frequent checking of seedbeds helps spot signsof pests or disease (Chap. 12). Appendix 12 summa-rizes the use and effectiveness of herbicides. Gener-ally, diseases are more serious than most insect at-tacks and are much harder to treat and control.

Because of the diversity in local climate, soils, andtree species planted, general pesticide recommenda-tions are difficult to make. Experienced forest pestspecialists are usually in short supply. But agricul-tural or horticultural specialists can usually handlemost problems because many insect and disease prob-lems affect crops as well as forest trees. Before specifictreatments are imposed, nursery managers must besure that they will not harm mycorrhizal fungi orother soil organisms. In severe cases, pesticide treat-ment and subsequent reinoculation with mycorrhizalfungi may be needed.

16.4.4 Fertilizers . -Fertilizers and organicamendments are essential for commercial nursery op-erations. Both kinds of nutrient supplements helpmaintain the nutrition of soils that produce nurserycrops for decades, sometimes for a century. Specialmonitoring of soil fertility, including acidity and solu-ble salts, is needed (Chap. 13).

Fertilizers can be applied in several ways. For largeoperations, slow release granules are drilledalongside seeds at sowing; they dissolve within 6 to 8months after application. Water soluble fertilizerscan be incorporated into irrigation water, but thistechnique is less preferred than incorporating granu-lar fertilizers in seedbeds because it requires moretechnical expertise in mixing and maintaining saltsat acceptable levels. Specific fertilizer formulationswill depend on the recommendations made after soilsamples are analyzed.

16.4.5 Inoculation with Mgcorrhizal Fungi. -Asexplained in Section 16.2, soil sterilization controlsweeds and harmful soil microorganisms, but it alsokills mycorrhizal fungi. If plantations or scatteredtrees having mycorrhizal fungi exist close to the nurs-ery, reinoculation should occur quickly from wind-disseminated spores. In other areas, particularlywhere no native pines exist (as in native savannasand grasslands), artificial inoculation is required.

Techniques exist for applying vegetative inoculumwith seeds at sowing (Sec. 16.3.1). Usually, spore in-oculum is used. The procedure involves collecting duffand topsoil (O-2 cm) from underneath already-infectedtrees in nearby plantations, bringing the material tothe nursery, and grinding and incorporating it inseedbeds. An alternative method is soaking the mate-rial in large volumes of water and applying the watercontaining spores over nursery beds with sprayingequipment. Pesticide spraying equipment should notbe used unless it is thoroughly cleaned and no otherequipment is available. A few seedlings can be liftedat random from seedbeds in 4 to 6 weeks to checkinoculation success. If inoculation is unsuccessful, theseedlings have poorer root growth and develop severeyellowing of foliage (fig. 16-5A). Figure 16-5B showsproperly inoculated seedlings.

16.4.6 Root Growth Control. -Healthy, well-developed root systems help seedlings maintain vigor-ous development in the nursery and adapt quickly tonew environments after outplanting. Several opera-tions stimulate good root growth and development:wrenching, undercutting, and lateral (side) root prun-ing. Advantages of maintaining adequate shoot/rootratios are outlined in Chapter 11.

16.4.6.1 Wrenching. -Repeated wrenching is aneffective method of stimulating lateral root develop-ment in the seedlings of some species, including P.radiata (3) and P. caribaea (16).

Wrenching is done with a tractor-mounted bladethat moves back and forth under the seedbeds. For-ward blade travel is about half that of sidewaystravel. The wrenching blade is tilted at a 15” to 20”angle, which heips lift-up the soil. Lifting-up and sub-sequent falling-back of soil on the seedbeds leavemany cracks in the soil, providing good aeration inthe root zone and resultant bushy root growth. Thefirst wrenching is done about 10 cm below the surface.Subsequent cuts are made at 21- to 30-day intervals,about 15 cm below the surface.

The wrenching blade must be kept extremely sharpfor a smooth, clean cut. The first wrenching should bemade as soon as seedlings average about 18 cm inheight; evidence suggests that lateral root develop-ment on the tap root is greatest for young tap roottissue. Thus, if wrenching is delayed too long, theupper part of the tap root is unable to develop lateralroots.

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Figure 16-5.-(A) Uninoculated seedlings. fB) Properly inoculated pint? seedlings have visible myeorrhizal fungi-root associations within 4 to6 weeks.

Lateral bushy roots that develop after wrenchingare very small in diameter and are delicate. Specialcare must be taken to avoid stripping these 3rd-, 4th-,and Fith-order roots from the seedlings during lifting.To some degree, lateral root pruning negates the ben-efits of wrenching because a large percentage of theroot system is lost in lateral pruning.

Seedlings with large, bushy root systems have highfield survival (15). Abundant roots formed fromwrenching absorb water well and regenerate newrootlets readily after seedlings are outplanted. How-ever, frequently wrenched seedlings have lesseramounts of carbohydrates and lipids than un-wrenched seedlings. These “food reserves” may be im-portant for survival of bare-root seedlings, particu-larly in times of drought stress following outplanting.

16.4.6.2 Lateral Root Pruning. -Lateral root prun-ing is an operational procedure in which roots grow-ing between seedling rows are severed. Afterwards, itis easier to lift seedlings because the remaining rootmass is confined to within the rows. Lateral root prun-ing is done immediately before lifting. This procedurealso cuts down on the time required to separateseedlings during grading and packing.

The most popular method of lateral root pruning iswith a tractor-mounted rolling coulter driven down

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seedbeds with coulter blades between the seedlingrows. Coulter blades must be kept between the rows,otherwise seedlings will be sliced and destroyed.There is no evidence that lateral root pruning stimu-lates additional primary lateral root growth; it doesstimulate secondary and tertiary lateral root branch-ing.

16.4.6.3 Undercutting. -Undercutting stimulateslateral root branching and stops shoot growth (13,17).Undercutting is done by pulling a rigid blade with asharpened leading edge that cuts the tap root clean(fig. 16-l). If the tractor speed is too fast and the soilis too wet, seedlings, can be pulled underground. Thesame problem occurs if the blade is dull or if seedlingsare too small and have insufficient lateral roots foranchorage. Failure to lower the blade soon enoughbefore entering the beds causes high seedling losses(fig. 16-6).

Undercutting has some negative aspects. The mostserious problem is the plow pan created by pulling theblade at the same depth. Plow pans impede drainageand may cause J-root-shaped root systems for manyseedlings.

The first undercutting is at about 18 to 29 cm belowthe surface. A second undercutting is usually suffi-cient to curb excessive height growth of dominant

Figure 16-6.-Undercutting losses in bare-root pine beds when tractor operator lowered the hydraulicblade too slowly.

seedlings. However, if a third undercutting is needed,it should be done at least 1 month before seedlings arelifted; this gives them time to repair wound damageand to recover from the general shock of large rootloss.

After undercutting, seedlings should be overwa-tered. Because they have lost most of their tap root,they need excess soil moisture so that the remainingportion of tap root and the lateral roots can maintaina proper water balance in the plant.

16.4.7 Shoot Growth Control

16.4.7.1 Top Pruning. -Most conifer seedlings aretop-pruned after the fifth month, after 30 percent ofthe seedlings are between 25 and 30 cm tall. Top prun-ing slows the height growth of seedlings that threatento suppress slower growing seedlings; unprunedsmaller seedlings continue to grow (14). The end re-sult is seedlings of more uniform height at lifting.Clipped seedlings do not develop new shoot growth forat least 3 or 4 weeks after clipping.

Top pruning also fosters a more uniform shoot-to-root ratio among seedlings. Removing growing shootsfrom dominant seedlings results in less carbohydratetransfer to the roots and, consequently, less rootgrowth. Thus, top pruning is a tool for developingseedlings of different morphological classes and forincreasing root biomass while keeping shoot biomassconstant. Seedling stem diameters also increase aftertop pruning.

Top clipping is done with flat rotary mowers, sickle-bar mowers, and reel-type cutters; all are pulled be-

hind tractors. Problems that arise from top pruningare: 1) seedlings are accidently cut back too shortwhen mowers hit low spots in the tractor paths and2) wounded stems and needles serve as entry pointsfor disease organisms such as brown spot needleblight.

16.4.7.2 Hardening-Off. -Reducing watering fre-quency in hardening-off slows shoot growth and re-duces production of succulent foliage. Hardening-offis needed for both container-grown and bare-root-grown seedlings. A more thorough discussion of thissubject is given in Chapter 11.

16.5 Lifting and Transporting

26.5.2 Historical Reuiew. --Lifting and preparingseedlings for distribution is a crucial process. In tem-perate climates having a well-defined dormant sea-son, seedlings are lifted and stored up to 120 dayswithout excessive loss of vigor. Seedling roots are keptmoist, and internal storage temperature is between 0and 4°C. Survival rates of 80 percent are expectedafter stored pine seedlings are planted.

Outplanting survival in temperate or tropical cli-mates is closely correlated to 1) adequate soil mois-ture at the time of planting and 2) adequate root re-generation in the soil before the dry season begins.Thus, it is always best to lift and outplant seedlingsearly in the rainy seasons (I, 5).

Historically, few bare-root planting operations forpine have been reported in the tropics. Venator andothers (20) reported that P. caribaea var. hondurensis

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was successfully bare-root planted when seedlingroots were kept moist, outplanting was done shortlyafter lifting, and sites had adequate soil moisture atthe time of planting. Since the late 1970’s, bare-rootpine stock has been successfully planted on a largescale (1,900 to 10,000 ha annually) in Venezuela andBrazil. With careful attention to detail, it should bepossible to expand bare-root plantings throughout thetropics, for conifers and hardwoods alike.

16.5.2 Lifting. -Lifting operations at large-scaletropical pine nurseries are similar to those used intemperate climates. Seedlings are undercut andmachine-lifted with care taken to keep roots moistand shaded from the sun. In Venezuela, liftedseedlings are kept moist in buckets of water, a proce-dure less messy and more effective than clay-waterslurries, sphagnum moss, and other alternatives (7).The crucial procedure is outplanting seedlings withina few hours after lifting. This process is not difficultfor a large corporation if 1) it has firm control over theentire operation, 2) it can organize and coordinateboth lifting and planting, and 3) it has access to goodroads.

16.5.3 Grading. -Grading is labor intensive, yet isnecessary because evidence shows that largerseedlings outgrow smaller seedlings (2, 4). Thus,smaller grade 3 seedlings, following Wakeley’s classi-fication (211, are inferior and should be culled fromthe seedling tables.

Some nurseries now grade on the basis of root collardiameters because larger diameter seedlings performbetter after outplanting (19). Grading by overaIl sizeand root collar diameter is much faster than gradingby shoot/root ratios and root area indices. Trimmingexcess lateral and tap roots before packaging is donewith machetes and chopping block or hand shears.

Low sowing rates (i.e., low seedling densities) inseedbeds (Sec. 16.3.2) usually result in less intensiveculling practices during grading and packaging. Op-erations that do not cull in the nursery depend onplanting crews to cull rejects as they plant. Nurserycosts are reduced, but slightly higher planting costsexist because grading is an added step. Field gradingmust be done by trained, conscientious planters;otherwise, inferior seedlings will be planted, result-ing in eventual harvestable volumes that are lessthan those expected from superior grade seedlings. Ifcostly planting machines are used, nursery gradingsaves valuable time and money over field grading.

16.5.4 Packaging and Delivering. -If same-dayplanting is used, time consuming packaging in bales,bags, and wraparound crates is avoided (II 1. Hugemetal or plastic buckets and tubs filled with water areused to store seedlings temporarily between lifting/grading, transporting/delivering, and machine out-planting. Throughout lifting, grading, packing, anddelivering, seedlings must be protected against expo-

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sure to sun and wind, particularly at midday to earlyafternoon when the sun is directly overhead. Theprincipal safeguard against unnecessary injury toplanting stock is adequate supervision of workers bynursery supervisory personnel.

LITERATURE CITED

1. Barres, H. Effect of root exposure on Honduraspine planting stock. Turrialba. 15(4): 348-349;1965.

2. Baur, C. N. Nursery spacing and grading of slashpine seedlings. Research Note 5. Sidney, Aus-tralia: Division of Forest Management,Forestry Commission of New South Wales;1960. 7 p.

3. Benson, A. D.; Shepherd, K. R. Effect of nurserypractice on Pinus rudiata seedling characteris-tics and field performance: II. Nursery rootwrenching. New Zealand Journal of ForestryScience. 7(l): 68-76; 1977.

4. Briscoe, C. B. Lifting pine seedlings. Trop. For.Notes 3. Rio Piedras, PR: U.S. Department ofAgriculture, Forest Service, Institute of Tropi-cal Forestry; 1960. 2 p.

5. Briscoe, C. B. Early lifting of pine seedlings. Trop.For. Notes 10. Rio Piedras, PR: U.S. Depart-ment of Agriculture, Forest Service, Instituteof Tropical Forestry; 1962. 2 p.

6. Cordell, C. E.; Kelley, W. D. Soil fumigation inSouthern United States forest tree nurseries.In: South, David B., ed. Proceedings, Interna-tional symposium on nursery managementpractices for the southern pines; 1985 August4-9; Montgomery, AL. Auburn, AL: AuburnUniversity, School of Forestry, Alabama Agri-cultural Experiment Station; 1985: 496-504.

7. De Camino, Ronnie. Personal communication.Gerente de Investigaciones. Compariia Na-cional de Reforestation (CONARE), Caracas,Venezuela. 1983.

8. Dennison, Steve A.; Messner, Harold E. Controlof line expansion in drip irrigation systems.Res. Note RM-427. Ft. Collins, CO: U.S. De-partment of Agriculture, Forest Service, RockyMountain Forest and Range Experiment Sta-tion; 1983. 2 p.

9. Fishwick, R. W. Irrigated nursery practice in-struction. Kaduna, Northern Nigeria: Ministryof Animal and Forest Resources; 1966. 19 p.

10. Hallman, R. G. Equipment for forest nurseries.In: Duryea, Mary L.; Landis, Thomas D., eds.Forest nursery manual: production of barerootseedlings. The Hague, The Netherlands: Marti-nus Nijhoff/Dr W. Junk Pub.; Corvallis, OR:Forest Research Laboratory, Oregon State Uni-versity; 1984: 17-24.

11. Lantz, Clark W. Handling and care of Southernpine seedlings. In: South, David B., ed. Proceed-ings, International symposium on nurserymanagement practices for the southern pines;1985 August 4-9; Montgomery, AL. Auburn,AL: Auburn University, School of Forestry, Al-abama Agricultural Experiment Station; 1985:118-125.

12. Leonard, Dave. Soils, crops & fertilizer use or awhat, how and why guide. Reprint R8. Wash-ington, DC: Peace Corps. 1980. 162 p. 3d ed.

13. Marrero, Jose. Efecto de la poda radicular des dosespecies forestales. Caribbean Forester. 8: 241-244; 1947.

14. May, Jack. Seedling quality, grading, culhng andcounting. In: Lantz, Clark W., ed. and camp.Southern pine nursery handbook. Atlanta, GA:U.S. Department of Agriculture, Forest Serv-ice, Southern Region; 1984: 9-l to 9-10.

15. Minko, G.; Craig, F. G. Radiata pine nursery re-search in North-Eastern Victoria. Forest Com-mission Bull. 23. Melbourne, Australia; 1976.24 p.

16. Napier, Ian. La poda de raiz de Pinus oocarpa y elPinus caribaea en 10s viveros de Honduras. Ar-ticulo Cientifico 5. Siguatepeque: Escuela Na-

cional de Ciencias Forestales, CorporationHondurena de Desarrollo Forestal; 1982. 15 p.

17. Nobles, R. W.; Briscoe, C. B. Root pruning of ma-hogany nursery stock. Res. Note ITF-7. RioPiedras, PR: U.S. Department of Agriculture,Forest Service, Institute of Tropical Forestry;1966. 4 p.

18. Thompson, B. E. Establishing a vigorous nurserycrop: bed preparation, seed sowing, and earlyseedling growth. In: Duryea, Mary L.; Landis,Thomas D., eds. Forest nursery manual: pro-duction of bareroot seedlings. The Hague, TheNetherlands: Martinus Nijhoff/Dr W. JunkPub.; Corvallis, OR: Forest Research Labora-tory, Oregon State University; 1984: 41-49.

19. Venator, C. R. The relationship between seedlingheight and date of germination in Pinus carib-sea var. hondurensis. Turrialba. 23(4): 473-474; 1977.

20. Venator, C. R.; Munoz, J. E.; Barros, N. F. Rootimmersion in water; a promising method forsuccessful bare-root planting of Honduras pine.Turrialba. 27(3): 287-291; 1977.

21. Wakeley, Philip C. Planting the southern pines.Washington, DC: U.S. Department of Agricul-ture, Forest Service; 1954. 233 p.

109

Appendices

The Why and How-To-Do-It Section

Appendices are not ordered consecutively but refer to actual chapters wherea major topic is discussed. For example, the first is Appendix 4 because shadingand nursery bed orientation are discussed in Chapter 4.

111

Appendix 4

Shading Procedures for Small, Covered Nursery Beds in Tropical Areas

113

The sun’s angle of inclination at a nursery site andthe orientation of seedbeds are used to determineshading arrangement. The following example can beused to determine positioning of shade cover oversmall seedbeds. For simplicity, it is assumed that thesun rises at 6:00 a.m. and is perpendicular to the nurs-ery beds by 12:00 noon, i.e., directly overhead (fig. A4-1). Thus, the sun has moved through a 90” arc in6 hours at a rate of 15” per hour. The problem is thenreduced to one of trigonometry, where the distance ofpenetration under the shade is:

Table A4-1 summarizes various penetration distancesof the sun for several shade heights.

Puerto Rico lies approximately 18” N. latitude fromthe equator. For a short time during the year, the sunis to the north of Puerto Rico as it changes from 18” to23” N. and back again. During this period, maximumshade protection is obtained by tilting the shade roofaccordingly.

Shade screens should be placed about 1.0 to 1.5 mabove 1.0-m nursery bed walls and extend about 0.3 to0.5 m past bed edges. Such placement allows workersaccess to tend seedlings without much extra effort.

Depth of sun penetrationunder overhead shade

Height of shade above seedbeds= Tangent of the sun’s angle of elevation *

ROOFACCORDINGTO LOCALLATITUDE

SIDE SHADEOVERMANG-- - - - e m - -

Sl4 IIIDE-ED I#UP

B A C K V I E WN

S I D E V I E W

Figure A4-l.-Small shaded nursery beds in tropical areas are best oriented in east/west direction; shade roof is tilted to sun according to locallatitude (e.g., ? 18” in Puerto Rico). At early and late hours of the day, shade screens are rolled down to keep out low angle rays.

Table Al-L-The penetration distance of sunlight under overhead shade for different heights atdifferent hours throughout the day

Hours Sun’s angle Tangent sun’s Depth of sun penetrat ion Cm)of a n g l e of when shade height (m) i s . . .A.M. P.M.

e l e v a t i o n elevation 0.6 0.8 0.9 1.1 1.2 1.8 2.1

7:oo 5:oo 15" 0.27 2.3 2.8 3.4 3.9 4.6 6.8 8.08:00 4:oo 30" 0.58 1.1 1.3 1.6 1.8 2.1 3.2 3.79:oo 3:oo 45" 1.00 0.6 0.8 0.9 1.0 1.2 1.8 2.1

lo:oo 2:oo 60" 1.73 0.4 0.4 0.5 0.6 0.7 1.1 1.2ll:oo l : o o 75" 3.73 0.2 0.2 0.2 0.3 0.3 0.5 0.6

114

Appendix 5

Flow Chart for Scheduling Mechanized Production of Container Nursery Stock

115

1. Receive seedling 2. Furchase seed on basis 3. Inspectandrepairquipnent:=Cl=S~ of viability report WateriIq systen

pzmzrdrivenequipnentpesticide applicatorstractors and forkliftssoilloadersakl shredderssoilmixerssoil sterilizers

8.

9.

16.

17.

18.

24.

seed germination 7. Preparegerminating 6. Fill containersbeds or Adirectseed

-

protectionfranbirdsandmice

Check germinationtimes daily for:waterinsectsdiseasehunidity

11. Cull nultiple seededCOIltdinerS

1

Mruveshadeafter6-8 eeks

cutp1antwhenseedlings are6-8 months old

15. Change insectand disease

14. Clsck 2-3 times dailyfor:

\checks to waterneeds

Tdailybasis+$in

fertility

19. ~infertili.zatim 20. cull and gIulpafter2montbs;apply seedlings by size:monthly thereafter water after glmuping

v23. Afterhardening-offandbefore

outplanting,checkandseverallrmtsthathavepemtratedintosoilfmnbagsorbloclm

4.

5.

12.

13.

21.

Inventory supplies:OontainerSshade mataialsgeminaticmmdiapesticideshandtoolsgenninatirq flatsfertilizerslabelsreoordfonnsmiscellanwusitem

Sterilizegeminationmdia

Line+utfilledcontainexs :shadelabels

l?mnsp1antifnecessary 2-3 daysafter germination;begin !iwn?ivalcounts

Measure heights at120 and 200 days:mean heights of 20Plats

Appendix 6

Non-Oven Procedures for Drying Pine Cones, Mahogany Pods, or SimilarSeed-Bearing Fruits at Traditional Nurseries

117

Ground Drying

Cones, pods, and fruits are spread out on a smooth,dry surface similar to that used for drying coffeebeans; radiant energy is used for drying. This methodworks when seed viability is not appreciably affectedby open exposure and when seeds are extremely abun-dant. Many small, temporary nurseries use thismethod to extract seeds.

Drying fruits on the ground involves several prob-lems. Rodents and birds can feed on seeds. Protectingseeds requires constant attention by laborers whomay be more profitably employed elsewhere. Whensudden showers occur, seeds or pods must be picked upand taken into a sheltered area. When several consec-utive rainy days occur, mold and fungus can attackbagged moist cones or pods. Likewise, outdoor sur-faces must be dry before cones are respread. Finally,cones or pods must be turned frequently so thatshaded undersides are also dried. In summary, open-air drying is best only for small seed lots.

Elevated Drying

This method of seed drying is also inexpensive. Theequipment used is elevated racks with screen bottomsthat allow air to circulate from above and below(fig. 6-1). A hinged top can be added for covering cones

or pods during light showers. As soon as the rainstops, the top can be removed for renewed drying.Cones should not be piled more than 4 to 5 layers deepin such racks. If a solar dryer is available, cones canbe dried in 3 to 4 days. A small solar dryer is a wiseinvestment for permanent nurseries.

A complementary method of drying cones or podsrapidly is placing them on drying racks over a lightfire. Empty cones or pods from the previous year’scollection can be used for fuel. However, extreme caremust be used in spreading burning coals uniformlyunder the drying racks to prevent spots where hottemperatures would roast cones and seeds. As heatedair from the fire rises, it passes through the cones anddries them. With experience, one can control this kindof fire so that air temperature in the area of the conesis kept at less than 38°C. Where conditions permit,combined use of air conditioning by day and dehumid-ifying by night will open P. curibuea cones within 3 to4 days of storage in office or laboratory buildings.

As soon as cones or pods begin to open, they shouldbe placed in a large tumbler and rotated until theseeds fall out. After falling free from the tumbler, theseeds should be dewinged, cleaned, and dried down toa moisture content of 8 to 10 percent and prepared forcold storage. Mahogany seeds should be dewinged anddried to a moisture content of 10 to 12 percent beforestoring under refrigeration.

118

Appendix 8

Summary of Seed and Nursery Characteristics for Forest Tree SpeciesCommonly Growing or Planted in Tropical and Subtropical Regions’

119

SpeciesNo. seeds

per kilogramStorage

recommendedPresowingtreatment

seedingmethod

Specialrequirements

Germinationand groeh

Acacia SenegalWilld.

7to8thousand.

None Boiling water tillcool.

Potted or directsown.

. . . . . . . . . . . . . . . . . . . . No data available ongermination. Plantablesize in 3-4 months.

Seedlings requireshade.

Germinates in 7-14days. Plantable size in12-18 months.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _......

Very susceptible todamping-off.

Germinates in 7-14days. Plantable sire in3-4 months.

Require 50% shade. Germinates in SO-100days. Plantable size in21-27 months.

Susceptible to No data available ondamping-off and re- germination. Plantablequires 50% shade. size in 18-24 months.

Require 75% shadein early months.

No data available ongermination. Plantablesize in 18-24 months.

. . . . . . . . . . . . . . . . . . . . Rapid and uniformafter lo-12 days.Plantable size in 11-14months

. . . . . . . . . . . . . . . . . . . . Germinates in 8-20days. No data ongrowth in nursery.

. . . . . . . . . . . . . . . . . . . . . .

NoneAgathis dammumL.C. Richard

16 to 21thousand.

Soak in cold waterfor l-2 days.

Potted

Albiziu Zebbek(L) Benth

Anthocephalus chinensist lamk) Rich

1 to 11thousand.

6 million.

Ambient temperaturefor several years.

Dry, cold, and airtightfor up to 1 year.

Boiling water tillcool.

None

stumps; directsown.

Potted

None

None

None

Potted

Potted

Potted

Araucaria angustifolia(Bert) 0. Kuntze

100 to 200. None

Amwaria cunninghamiisweet

2.4 to 2.8thousand.

None

Amucaria hunsteiniiK. Schumann

1.7 to 1.8thousand.

None

None Soak in cold waterfor l-2 days.

Azadimchta indictiA. Juss

4 to 4.5thousand.

Potted; stumps;direct sown.

Bombacopsis quinutum(Jacq.) Dugand

2.3 to 2.7thousand.

. . . . . . . . . . . . . . . . . . . . . . None stumps

Dry, cold, and airtightfor several years.

None PottedCallitris glnucaR. Br. ex R.T. Bak etH. G. Sm.

Casio simneaL a m .

70 thousand.

35 to 40thousand.

Dry, ambient tempera-ture for several years.

Boiling water tillCOOl.

Potted, stumps;direct sown.

. . . . . . . . . . . . . . . . . . . . Good and uniform after7 days. Plantable sirein lo-12 months.

Casuariruz equisetifoliuL .

7OOto800 Ambient temperaturefor l-2 years.

None Potted; bare-rooted plant&

Shade in nursery. Germination in 40days. Plantable size in3-4 months.

Cedrella odoratnL.

Cordia alliodoraCham.

Cvptomeria japonicaDon.

Cupressus lusitanicaMill. lincl. C. ben-thamii Endl.)

Cvbistax donnellsmithii(Rose) Seibert

EucalyptuscamaldulensisDehn (Northern Prov.)

EucalyptuscamaldulensisDehn (Southern Prov.)

Eucalyptus degluptaBlume

Eucalyptus globulusLabill

Eucalyptus grandisHill ex Maiden

Eucalyptus robustaS M

Eucalyptus salignaS M

Eucalyptus urophyllaS. T. Blake

45 to 60thousand.

lto2million.

330 to 400thousand.

170 to 320thousand.

. . . . . . . . . . .

700 to 800thousand.

700 to 800thousand.

lto2million.

120 to 140thousand.

600 to 650thousand.

500 to 600thousand.

600 to 650thousand.

210 to 300thousand.

Dry, cold, and airtightfor l-2 years.

Dry, cold, airtight;shortlived viability.

. . . . . . . . . . . . . . . . . . . . . .


Dry, airtight in ambi-ent temperature for upto 1 year.








Dry, cold, and airtight.

None

None

None

Stratify in dampsand for 30 days.

. . . . . . . . . . . . . . . . . .

None

. . . . . . . . . . . . . . . . . .

None

None

None

None

None

None

Potted;striplings.

Stumps; directsown.

Potted or cut-tings.

Potted, bare-rooted plants.

Potted; stumps;bare-rootedplants.

Potted

potted

Potted

Potted; directsown; bare-rootedplants.

Potted

Potted

potted

Potted

Prefers some shadein nursery.

Low germination ca-pacity: use largeplants.

Frost-tender in nurs-ery.

Early shade benefi-cial.

Susceptible todamping-off. Be-quires shade.

. . . . . . . . . . . . . . . . . . . .

Good vegetativepropagator.



Germinates in 14-28days. Plantable size in12 months.

C&erminates in 35 days.Plantable size in 15-18months.








Germinates in l-20days. Plantable size in4 months.

Germinates in 7-12days. Plantrble size in4 months.

Appendix 8 (continued)

SpeciesNo. seeds

per kilogramStorage

recommendedPresowingtreatment

seedingmethod

Specialrequirements

Germinationand growth

Gmelina arboreaRoxb.

700 to 1,400.

Leucaena leucocephaln(Lam.) de Wit(Hawaiian type)

27 to 30thousand.

Leucaena leucocephala(Lam) de Wit(Salvador type)

26 to 30thousand.

Ochroma lagopus 70 to 100S W thousand.

Parkinsoniu aculeataL.

12 thousand.

Pinus merkusiiJungh & de Vriese(Island Prov.)

60 thousand.

Pinus occidentalisSwartz

Pinus oocarpaSchiede

41 to 55thousand.

Pinus pat&aSchiede and Deppc.

100 to 140thousand.

Pinus caribaea Moreletvar. bahamensisBarr & Golf

80 to 85thousand.

Shortlived viability, upto 1 year.




Ambient temperaturefor up to 1 year.

Dry for l-2 years.

None

Dry and cold for sev-eral years.



Soak in cold waterfor l-2 days.

Soak in water80°C for 2 min-utes.

Soak in water80°C for 2 min-utes.

Boiling water tillCool.

Soak in cold waterfor 3-6 days.

None

None

None

None

None

stumps; pottedplants or direct5xvn.

Potted

Potted


Potted

Potted

Potted

Potted

Potted, bare-rooted pbults.

potted

May require impor-tation of Rhizobiumstrain for nitrogenfixation.

May require impor-tation of Rhizobiumstrain for nitrogenfixation.

50% shade, but isvery susceptible todamping-off.

No grass stage. Fte-quires mycorrhizaand some shade.

Mycorrhiza required.

Mycorrhiza required.Susceptible todamping-off.

Requires mycorrhiza.Susceptible todamping-off.

Mycorrhiza essential.Susceptible todamping-off.


Germinates in S-10days. No data ongrowth in nursery.

Germinates in 8-10days. No data ongrowth in nursery.


Germinates in lo-14days. Plantable size in4-5 months.

Germinates in lo-12days. Plantable size in8 months.

No data available ongermination. Plantablesize in lo-12 months.




Pinus curibaea Moreletvar. caribaeaBarr & Golf

Pinus curibaea Moreletvar. hondurensisBarr & Golf

Pinus kesiyaRoyle ex Gordon

Pinus radiataD. Don

Prosopis julifloratSwartx1 D.C.

Samanea samanhlerrill.

Swietenia macrophyllaKing

Tectona grandisL.

Terminalia superbaEngl. and Diels

Toona ciliataM.J. Roem var.australis F v M

5 5 to 6 0thousand.

5 2 to 7 2thousand.

5 5 to 6 2thousand.

20 to 26thousand.

4.4 to 7thousand.

2 to 2.5thousand.

0.8 to 2thousand.

5.5 to 6.6thousand.

300 to 380thousand.





Without difficulty atambient temperature.

Dry, ambient tempera-ture for several years.


Dry without difficulty.


None

None

None

None

None

Leave in boilingwater till cool.

None

None

Soaking frequentlypracticed.

Alternately wetand dry.

None

Potted

Potted

Potted

Potted, bare-rooted plants.


Potted

Potted orstriplings.

Stumps or pottedstock.

Potted,striplings;stumps.

Striplings; pottedstock.

Mycorrhiza essential.Susceptible todamping-off.

Mycorrhixa essential.Susceptible todamping-off.

Requires mycorrhixa.Susceptible todamping-off.

Requires mycorrhixa.Susceptible todamping-off.

Requires full shadefor 2-3 weeks, thenhalf shade for 1month.

Several embryos perseed.

Requires light shadeaRer germination.




Germination is rapidand uniform. Plantablesize in 24 months.




Germination often pro-tracted. Plantable sizein 12 months.


‘Adapted from Webb. D.B., P.J. Wood, and J. Smith. 1980. A guide to species selection for tropical and subtropical plantations. University of Oxford, Commonwealth ForestInstitute, Tropical Forestry Paper 15. United Kingdom.

Appendix 9

Practical Guides for Fumigating, Sowing, and Transplanting

I. Recommended Procedures for Use and Storage of Soil FumigantsII. Calculation of Materials Required for Producing 1 Million Bagged Pine SeedlingsIII. Sowing and Transplanting Procedures for Importarit Species of Tropical TreesIV. Publications on Particular Tree Species

125

I. Recommended Procedures for Use and Storage of Soil Fumigants

GENERAL INFORMATION

Methyl bromine-chloropicrin (MBC) fumigant for-mulations consistently provide good soil treatment.The two most commonly used forms in forest treenurseries are MBC-33 (67 percent methyl bromide, 33percent chloropicrin) and MBC-2 (98 percent methylbromide, 2 percent chloropicrin). Over 90 percent ofall forest nurseries in the Southern United States useeither MBC-33 or MBC-2. MBC-2 provides broadtreatment of soil fungi, weed seeds, nematodes, andsoil insects. MBC-33, on the other hand, is used inspecific instances where more resistant root diseaseorganisms occur and where highly susceptibleseedling hosts will be grown (2).

In large bare-root nurseries, MBC fumigants areusually applied with chisel injectors to depths of 20 to25 cm. Where soil disease organisms threaten deep-rooted seedling species, fumigants can be injected to adepth of 30 cm or more. Dosage rates for large fieldapplications are 280 to 640 kg/ha.

For smaller nursery operations, MBC or other fumi-gant mixtures are applied to soil surfaces. The chem-icals are released from pressurized containers intoevaporating pans placed under polyethylene sheeting.This method is very suitable for treating smallseedbeds and transplant beds as well as for fumigat-ing compost medium used in container operations.Dosage rates for bulk materials are 0.59 kg/m3 foreither MBC-33 or MBC-2.

Because of its suitability for small nursery opera-tions, the pan evaporation method is described here indetail, using one MBC fumigant.

DOWFUME MC-2

Although only Dowfume MC-2 (hereafter calledDowfume) is discussed here, most procedures and cau-tions for its use and storage are applicable to otherfumigants (table 10-l). For specific use restrictionsand precautions, including toxicity to certain plantsor organisms, it is best to consult product labels andcurrent editions of yearly review guides, such as theFarm Chemicals Magazine (3 ) and the Weed ControlManual (I 1.

Dowfume contains methyl bromide with 2%chloropicrin added as a warning agent against over-exposure to methyl bromide. When a gas mask isworn, chloropicrin cannot be depended on as a warn-ing agent. Dowfume is applied under a gasproof coverwhen treating soil and other medium in whichseedlings are grown for nonfood and food crop uses.

126

Dowfume is a liquid under pressure while in thecontainer. It turns to a gas when released and must beconfined under a plastic or coated fabric gas-proofcover. Both liquid and gas forms are poisonous andmay cause burns on contact. The product label con-tains detailed instructions for use and handling pre-cautions.

INSTRUCTIONS

Seedbed Soil Preparation

Dowfume is effective only to the depth that soil isproperly prepared. Suitable treating conditions aremoist, fine, and loose soil having no lumps or clods.Soils should be moist but not wet; gas will not spreaduniformly through wet soils, and control of weeds andsoil pathogens will be poor. For best results, fumigateto lo-cm depth when soil temperature is above 16°C.If soil temperature is between 10” and 16°C doublethe recommended exposure time. Do not fumigate ifsoil temperature is below 10°C.

Dosage

Determine dosage from information on the productlabel. Dowfume controls most weed seeds, nematodes,and insects present in the soil at time of treatmentwhen used at recommended rates. Certain specieswith hard seedcoats may require a higher dosage orlonger exposure time.

Application Equipment

Materials required include evaporating containers,a gas-proof cover of polyethylene or other materialimpermeable to Dowfume, cover supports,polyethylene tubing, and an applicator to dispense thefumigant.

Dig a lo- to E-cm-deep trench around the border ofthe area to be treated; this provides an effective wayof sealing the gas-proof cover before releasing the fu-migant. Next, place cover supports at regular inter-vals on the prepared bed. They must be high enoughto hold the cover above the soil surface and evaporat-ing containers so that fumigant vapors circulatefreely. Supports must not puncture or tear the cover;they can be made from inflated polyethylene bags,crumpled fertilizer bags, burlap bags stuffed withstraw, inverted flower pots, bottles, or cardboardboxes (fig. 9-2).

With the supports in place, evaporating containersare set about 9 m apart in the area to be treated. Thecontainers aid volatilization and uniform dispersion

of the fumigant and keep it from soaking into theground as a liquid. Pan or basin materials that areused include glass, porcelain, and tin, but not contain-ers made of aluminum or its alloys. Containers shouldbe shallow, 4 to 5 cm deep at most; this depth allowsready dispersion of fumigant vapors and assures suffi-cient capacity to hold about a 0.2-liter volume for each0.7-kg can of Dowfume dispensed.

After placing the evaporating containers in thebeds, a polyethylene applicator tube is fastened toeach, with one end directed into the container. Tubesshould be long enough to allow easy attachment of thefumigant applicator.

The gas-proof cover is laid over the area to betreated, its edges placed in the trench previously dug,and the edges sealed with earth. Earth should coverthe edges to a width of 15 to 25 cm and be tampeddown firmly. During this operation, special care istaken to avoid damaging the cover. Covers will lastseveral years if handled and stored properly.

Apply Dowfume with a standard opener that punc-tures the can, gaskets the opening, and allows thefumigant to discharge through an attached tube intothe confined area being treated. When using any ap-plicator, these simple rules should be followed toavoid possible contact with Dowfume:

1. Place can in applicator cradle and draw handlequickly toward body of can until piercingpoint has entered the can and the gasket isseated. Avoid puncturing the can side seam,and keep the point of puncture at the lowestpoint on the can being emptied so that inter-nal can pressure forces all liquid from thecan. If the c,an is punctured high, fumigantvapors rather than liquid will flow throughthe tubing, and internal pressure will be re-duced so that it is difficult to get liquid outof the can.

2. Never open cans without checking that fumi-gant will be dispensed where desired.

3. Do not disconnect the applicator from can orfrom the polyethylene tubing until can iscompletely empty. The applicator does nothave a valve to stop fumigant flow after acan is punctured.

4. If the applicator breaks or fails to puncture andseal a can properly, keep away from the canuntil all the fumigant has evaporated andvapors are carried away.

Only one applicator is needed because it is trans-ferred from one polyethylene tube to the next. CAU-TION: Transfer applicator to next tube only ufZer thecan of Dowfume to which it is connected is completelyempty. Cans should be warm (15” to 32°C) so thatfumigant flows rapidly through the polyethylene tubeinto the evaporating container. After application is

complete, do not disturb either gas-proof cover orpolyethylene applicator tubes because gas may escapeand create a hazard to the operator and also reduceeffectiveness of the soil treatment.

An alternate method of application involves vapor-izing Dowfume before releasing it under the gas-proofcover. This method obtains a uniform concentration ofgas throughout the treated area as quickly as possi-ble. Because the fumigant is released as a gas ratherthan a liquid, evaporating containers are not needed.Dowfume is vaporized by puncturing the can in theconventional manner, immediately turning it upsidedown, and submerging both the punctured can andattached applicator in hot water. Keep submergeduntil empty. Additional water, kept hot by a camper’scook stove, should be kept available; the original hotwater supply will be cooled by rapid vaporization ofthe fumigant.

For the vaporization method, openers are designedspecifically for a 0.7-kg can and serve both as a can-piercing device and as an evaporation tray. They areused only for soil fumigation under polyethylene cov-ers.

Application procedures are:1. Place tray(s) (one for every 5-m2 area to be

treated) upright on prepared seedbeds.Carefully insert two 0.7-kg cans into nailguides at the bottom. CAUTION: Do notallow nail to puncture can.

2. With tray(s) positioned near edge of seedbed,cover tray(s) and bed with polyethylene,using soil to seal all edges in preparedtrenches. Walk toe-to-heal around entireperimeter, compacting solid to prevent windfrom breaking cover-earth seal during fumi-gation.

3. From outside the gas-proof cover, press palmdown firmly against each can in turn topuncture it against the nail. Use palm ofhand only--never use foot, board, shovel orother hard object that might tear the plasticand permit fumigant escape. Have maskingtape or plastic tape available to repair acci-dental punctures. Do not attempt to removetrays or cans until cover is removed, after a24- to 4%hour exposure period. The longerexposure period is needed when soil temper-ature is below 16°C.

Exposure and Aeration

The fumigated area is left undisturbed for the 24- to48-hour period. Remove cover and let the soil aeratefor 24 to 72 hours or more. Work it thoroughly tospeed further aeration. Some kinds of seeds can beplanted immediately after initial aeration. Sensitivespecies cannot be planted until after several days ofaeration. Do not set out living plants for at least 1week.

127

I NON-SOIL MATERIALS

Compost and Manure

Follow the general instructions above for soil treat-ment. Conduct fumigation outdoors or in a well venti-lated place. Materials should be loose, moist enoughfor good seed germination, and at a temperature~16°C. For best results, pile the materials 530 cmdeep on wet ground or on a concrete floor. Piles up to1 m high can, when necessary, be fumigated if perfo-rated every 30 cm. The cover is supported severalcentimeters above the material to permit gas to dif-fuse thoroughly. Dowfume is introduced at the highestpoint of the pile. After exposure, let the pile standcovered for 24 to 48 hours. Then the material is aer-ated for 1 day, stirred thoroughly, and reaerated 48hours or longer before using.

Mulches

Straw or hay should be thoroughly soaked severaldays before treatment. At time of treatment, pile thebales up, cover them with a gas-proof cover, and sealthe edges in the same manner as recommended forcovering soil.

USE PRECAUTIONS

Dowfume gives excellent results with a wide vari-ety of soils and plants. However, for reasons notclearly understood, plant growth has occasionallybeen unsatisfactory following treatment. Difficultyhas been experienced with carnations, conifers, holly,multiflora roses, snapdragons, and certain other orna-mental plants and shrubs. Every grower should ex-periment on a small scale for at least a full seasonbefore extensive use. For best results, observe the fol-lowing precautions:

1. Do not treat soil when it is cold, wet, or dry.2. Dowfume is toxic to all plants. Do not fumigate

too close to desirable vegetation. Keep edgesof the cover at least 30 cm away from rootsof desirable plants; water the root zone thor-oughly in the area not hooded by a cover. Ifpossible, pre-soak the root zone around de-sirable plants immediately adjacent to coverto help contain the gas under the cover.

3. Be sure the treated soil or material is free ofDowfume before seeding; working it willspeed aeration.

4. Prevent contamination of fumigated areas.Clean shoes carefully before walking fromuntreated to treated soil. Do not use tools,transplants, or crop remains that may carry

pests from nonfumigated areas.

5. Fumigation with Dowfume sometimes slowsdown the rate of nitrification (the conver-sion to nitrates from ammonia by bacterialaction). Certain ammonia-sensitive plants,such as tomatoes, may suffer growth inhibi-tion when planted in fumigated soils con-taining a high amount of ammonia nitro-gen. To lessen this hazard, at least one-half,and preferably all, of the nitrogen fertilizeradded immediately before or soon after fu-migation should be in the form of nitratenitrogen. This hazard may also be reducedby delaying planting until several monthsafter fumigation.

6. Fumigation of soils high in inorganic matter,such as muck, compost, and heavily ma-nured soil, may occasionally cause condi-tions of poor plant growth. These soilsshould be fumigated at least 2 months be-fore planting.

HANDLING PRECAUTIONS

Dowfume (or any other) fumigant is a highly haz-ardous material and must be handled carefully whilefollowing the precautions given below:

1. Before using, read all label directions and followthem carefully.

2. Do not breathe the vapor.3. Do not spill. If liquid Dowfume spills on shoes or

clothing, remove them at once and do notwear them again until they have been airedoutdoors for several days. Do not weargloves when applying Dowfume because thefumigant can be “trapped” in them, length-ening exposure time to human tissues.

4. Keep animals and children away from plots thatare treated and for at least 30 minutes afterthe cover is removed. The warning agent inDowfume that irritates eyes dissipates in afew hours; however, the irritant may notkeep children or animals from creepingunder the cover.

5. When fumigating inside buildings, keep doorsand windows open at all times until aerationis completed. Good ventilation is essentialfor safety and for satisfactory aeration, par-ticularly when fumigating compost and ma-nure.

6. Store Dowfume in a cool place away fromdwellings.

7. Applying Dowfume outdoors often eliminatesneed of a gas mask during application; how-ever, always keep one on hand for emer-gency use.

8. Always have a helper to assist with applicationand for any emergency that may occur.

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II. Calculation of Materials Required for Producing1 Million Bagged Pine Seedlings

POTTING MEDIUM

In the following calculations, it is assumed thatvented plastic bags (20 cm long by 10 cm wide) areused. The first step is determining how many bags 1m3 of medium will fill. Flat folded bags (20 by 10 cm)have a circumference of 20 cm (2 by 10 cm = 20 cm).Therefore, the diameter of the filled bag is:

c = 3.14D, where C = circumference,20 cm = 3.14 D or D = 2013.14, D = diameter,

D = 6.37 cm and 3.14 = T.

The area (A) of the base (i.e., circle) of the bag iscalculated by the formula A = r2v. Since diameterequals 2 radii (r), r is determined:

D = 2r = 6.37 cml2,r = 3.18 cm.

Once r is known, the area (A ) of the container baseis determined:

A = (3.14)(3.18 cm)” orA = (3.14)(10.11 cm2),A = 31.8 cm2.

Then the volume of the plastic bag (i.e., a cylindri-cal container) is calculated:

V =AL, where V = volume,V = (31.8 cm2)(20 cm), L = length,V = 636 cm3 and A = area of base.

One m3 of medium contains 1 million cm3. There-fore, the number of bags that can be filled with 1 m3is:

1000 0009 9 cm3/m3=6 3 6 cm3/bag

l,OOO,OOO cm3 x 1 b a gm3 636 cm3 -

1,572 bags, or 1,570 bags per 1 m3 of medium whenrounded for ease of calculation.

Allowing 15 percent cull mortality, about 1,150,OOOtilled bags are actually needed to produce 1 millionseedlings (see Sec. 52.1). Therefore, the total numberof cubic meters of potting medium needed to fill thebags is:

1,150,OOO bags/l,570 bags per 1 m3 of potting mate-rial = 732 m3, or 730 m3 when allowing for waste.

One commonly used pot mix is 5 parts sandy loamsoil, 1 part sand (11.70 mm sieve), 1 part sand (~1.40mm sieve), and 2 parts organic material (~1.25 mm)such as thoroughly decomposed sawdust, leaves, oragricultural byproducts.

A small quantity of slow-release granular fertilizer(no more than 4 cm3 per bag) can be mixed into thepotting medium to supplement medium nutrient con-centration. A 12- to 15-month slow-release formula-tion will carry over in the field and give seedlings anadditional boost. An appropriate volume ratio is 1 m3of fertilizer per 200 m3 of potting medium. Fertilizershould be mixed into potting medium that has beensieved to ensure a complete mixture. The amount ofpotting medium necessary to fill 1,150,OOO bags isbroken down into the following components:

730 m3/9 parts = 81 m3 per component,

or

Pot Media Component Mix Component Volume

sandy loam soil (5) x (81 hi? = 405 m3sand (2) x (81 m3) = 162 m3organic matter (2) x (81 m3) = 162 m3

fertilizer (1 m3) x- - = 3.6 m3 (rounded to 4.0 m3)(200 m3) (730 m3)

The total pot mixture volume needed to produce1,150,OOO seedlings is 730 m3 of medium + 4 m3 offertilizer or 734 m3.

POLYETHYLENEBAGS

Vented-type bags should be purchased because thesmall, pre-punched holes in the bag drain excesswater. Bags are generally sold in units of 1,000 perbox. Therefore, the number of boxes required is:

1,150,OOO bags/l,000 bags per box= 1,150 boxes.

SEEDS

Upon request, seed suppliers will furnish buyerswith an estimate of the number of seeds in each kilo-gram. Most seed dealers also supply area of collectionand other seed source information about seeds. Thegermination information is generally notorized by anindependent seed testing laboratory. Assume that P.caribaea var. hondurensis has 52,800 seeds per kg andthat the seed supplier certifies a germination rate of75 percent. With this information, the seed require-

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merit is calculated. Because of the germination rate of75 percent, 3 seeds are sown in each bag:

(3 seeds/bag) x (1,150,OOO bags)(39,600 viable seeds/kg)

3,450,OOO seeds= 39,600 viable seeds/kg

= 87.1 kg of seeds required for all bags(rounded to 88 kg).

Only the early germinants should be kept in eachbag (4). Later germinants are thinned out or trans-planted into bags in which none of the 3 seeds germi-nated.

III. Sowing and Transplanting Procedures for Important Speciesof Tropical Trees

The eight procedures described below have workedwell at the ITF nursery in Rio Piedras and the Mon-terrey nursery in Dorado, Puerto Rico. They shouldwork well in other nurseries where similar germina-tion beds and medium are available. In most in-stances, a local substitute for commercial productsexists (e.g., rice hulls for vermiculite and sterilizedcompost for peat moss). Also, procedures should beapplicable to different species within the same generaor same seed type (e.g., Pinus sp., tiny seeded species,and species with hard seedcoats needing scarificationbefore sowing).

1. Pinus caribaea and Pinus oocarpa

Pinus sp. seeds are spread evenly over germinationmedium at least 10 cm deep. No more than 1,000 seedsshould be sown per 30- by 30-cm area of each germina-tion tray. This is a high sowing rate, but less than 70percent of germinated seeds are usually transplanted.Moreover, because seedlings are transplanted 3 to 6days after germination, seedbeds are rapidly thinned.

Seeds covered with 1 cm of grit, sand, or vermiculitegerminate without difficulty. Unlike for temperateclimate pines, seed scarification and stratification arenot necessary. Germination bed shade boxes (fig. 5-2)are either hinged or closed securely at the top. Wirescreens (1.3 cm square mesh) over the top keep seedpredators away. Some nurseries germinate Pinuscaribaea seeds in the dark. However, we found that30- to 50-percent Saran shade gives excellent germi-nation in Puerto Rico.

2. Anthocephalus chine&s (Kadam)Seeds of this species are extremely small (about 6

million seeds per kg). Care is needed to avoid washingseeds from seedbeds. Seedlings are raised on aeratedloose germination medium, preferably sterilized fine

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sandy loam soil, spread to a depth of 7 to 8 cm insidegermination flats. A 3-ply layer of tissue paper (Kim-pak) is spread over the soil, and seeds are sprinkled ontop (fig 9-5). The tissue prevents the seeds from sink-ing into the soil.

Kimpak lasts about 2 to 3 weeks before decomposi-tion occurs; the seeds germinate in this period. A verylight cover (0.3 cm) of fine, dry, sandy loam soil can besprinkled over the seeds to keep them moist; other-wise, exposed seeds will dry out rapidly. White Kim-pak material allows control of sowing density by vi-sual inspection because dark seeds contrast wellagainst the paper. Kadam germination flats should bewatered with a Fogg-it-type nozzle or with overheadmist sprays. A clock-controlled high pressure mistingsystem works well. The timer is set to spray water for10 seconds every 30 minutes, the spray rate beingadjusted according to ambient humidity. Wateringfrom below also avoids dislodging seeds.

Saran shade (50 percent) is placed 25 to 30 cm abovethe germination beds. Sides left open allow light tofall on the flats. A plastic sheet placed about 1.8 mabove the flats protects seeds from being dislodged byrainfall. Because kadam seeds are small, neitherbirds nor rodents bother them. Once germination hasbegun, moisture content of the germination beds iscarefully controlled to avoid damping-off.

Proper transplanting time occurs when seedlingsform at least four small leaves above the cotyledons,when seedlings are approximately 2 cm high.Seedlings are lifted by holding the leaves and pullingupwards gently, simultaneously lifting roots frombelow with a spatula. Because kadam seedlings forma very branchy root system, they must be trans-planted almost immediately after germination.Avoiding J-roots in transplanting is done by trim-ming tap and lateral roots to about 3 to 5 cm, pullingthem through a dish of water, and planting them incontainers (Sec. 10.1.1).

3. Gmelina arborea

The fruit of Gmelina is quite large, with 700 or moredrupes/kg. Seeds are sown with 1 cm of light covering(rice hulls, vermiculite, etc.) so that the radicleemerges from the bottom side to prevent J-roots.Gmelina is generally direct-seeded into beds or bagsso that each seed has a minimum of 6 cm2 of growingspace. The maximum growing space recommended is10 to 11 cm2. Germination medium is kept moist butwell-drained to prevent damping-off.

Since Gmelina is generally stump-planted, germi-nation beds having loose sandy soil are ideal forundercutting. A loose soil readily shakes free fromroots at lifting. A light shade of not less than 20 per-cent or more than 45 percent is used during germina-tion but is removed after 3 weeks. The seeds must beprotected from mice and birds.

4. Swietenia sp. (Mahogany)

Most Swietenia seedlings are planted as bare-rootstock. The major problem is formation of J-roots. (fig.10-l) because of the peculiar method of mahoganyseed germination. Seeds should be dewinged and scat-tered on top of germination flats or beds, never pushedinto the ground with the wing protruding. As germi-nation begins, the hypocotyl emerges opposite theseed abscission scar and turns downward to establisha root system. The epicotyl develops from thehypocotyl and leaves are formed; cotyledons remaininside the seed, which eventually shrivels and fallsoff. Germination medium must be loose, permittinguninhibited hypocotyl development.

Dewinged seeds are broadcast on level, well-drained beds. A light covering (about 5 mm) of ver-miculite, fine sand, or rice hulls (never clay soil) isscattered over the sown seeds. This cover retainsmedium moisture around the seeds, avoiding fluctua-tions in seedbed moisture. Saran shade cover (up to 50percent) can be used during the germination stage.Fresh mahogany seeds germinate within 5 to 7 days.Seedbeds are watered two to three times a day if nec-essary. If sufficient shade is used and if germinationmedium does not have wide fluctuations in moisture,seeds can be sown directly on top of seedbeds withoutcover.

5. Eucalgptus

Although Eucalyptus sp. are easily regenerated inthe nursery, they have small seeds, often more than400,00O/kg. Thus, sowing methods are used that avoidapplying too many seeds to germination trays. In onemethod, similar-size sand grains or a dead seed lot aremixed with live seed. The mixture is put inside a saltshaker and sprinkled over the germination beds (fig.9-5). With practice, workers can develop a fairly uni-form delivery rate.

In another method, small amounts of seed areplaced in a dish. Workers then gently touch the seed

with a moistened stick. Generally, two to three seedsadhere to the stick and are placed in containers (fig.9-5). This process is laborious but fairly effective.After several weeks, the containers are checked formultiple seedlings, and the weakest seedlings areculled.

Following sowing, seeds are covered with a lightlayer (about 0.3 cm thick) of fine sand or fine vermic-ulite that is kept moist. Watering is done with a mistnozzle. At least 30-percent, perhaps as much as 50-percent, shade is used to keep germination mediummoist and to shield seedbeds of trays from direct rain-fall that would dislodge seeds.

6. Tectona grandis (Teak)

Teak seeds are difficult to germinate because theyare enclosed within an extremely hard seedcoat.Methods to hasten germination are scarification withhot water or sulfuric acid (Sec. 61.2). Once the seed-coat is broken, water is taken up and germinationbegins, being essentially complete within 2 months.

After scarification, seeds are placed in large flats,slightly elevated for drainage, and filled with a 3:lmixture of sand and loamy soil. The seeds are placedon the bed, covered with a l.O- to 2.0-cm layer of thesame mixture, and then watered. A 30-percent shadekeeps beds from drying out. The seeds are sown at avery dense rate of about 200 per 30- by 30-cm area.

Seedlings are transplanted when they have fourleaves. They are handled by the leaves, with the rootsbeing lifted out with a spatula. Soil and roots are keptmoist between lifting and transplanting. In mostcountries, seedlings are lined-out in ground-level bedsfrom which they are lifted as stumps and planted. Insome countries, because of the way it is field-planted,teak is produced in containers.

In large operations, seeds are sown in drills at lo-cm spacing. As they germinate, they are lifted whenready, and new seeds are dropped into the emptyspaces in the rows. This method is inefficient, how-ever, because a large area is used for a small crop, andcontrol of shading and moisture is more difficult.

7. Leucaena leucocephalu

Leucaena seeds, like those of other legumes, havean impervious waxy seedcoat that must be treatedbefore seeds will germinate. Soaking with hot water(80°C) for 2 to 3 minutes, and additional soaking inwater at room temperature for 2 to 3 days, yields upto 80-percent germination.

In nurseries, seeds are sown in germination flatswith sand, vermiculite, and soil, about 1,000 seeds per30- by 30-cm area, and are transplanted to pots. In thefield, seeds are direct-seeded on bare mineral soil thatis free of weeds. Young seedlings are easily shaded-out by fast-growing weeds. However, once rapidagrowth has started, field-planted Leucaena seedlingsform a dense mat that shades out weeds and other

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plants. Inoculation with a Rhizobium strain may beneeded in areas not planted to Leucaena previously.

Stems of old and young Leucaena trees sprout vigor-ously when cut. Several rotations of 5 to 8 years arepossible from one root stock. Once vigor is lost, treesmust be replaced with new seedlings.

8. Acacia mangium (Mangium)

Mungium seeds also have an impervious seedcoat.Soaking in hot water (boiling water just removed froma heat source) for 30 seconds and soaking in tap water

overnight breaks the seedcoat. The 30-second treat-ment time should be followed closely, as well as aseed/hot water volume ratio of 1:lO.

The seeds are broadcast on nursery beds and cov-I

ered lightly with fine sand or soil. Germination startsin 2 or 3 days and is complete in 8 to 10 days.Seedlings are transplanted to pots when the first pairof leaflets form. Direct-seeding in pots is also possibleif seed germination is high. Seedlings reach outplant-ing size, 25 to 30 cm tall, in 2 to 3 months. Nodules onroots should be visible before outplanting; if not, inoc-ulation with a Rhizobium strain is needed.

IV. Publications on Particular Tree Species

1. Armitage, F. B.; Burely, J. Pinus kesiyu Royle exGordon: (syn. P. khusyu Royle; P. insularis(Endlicher). Oxford: University of Oxford,Commonwealth Forestry Institute. TropicalForestry Papers 9; 1981. 199 p.

2. Cooling, E. N. G. Pinus merkusii. Oxford: Univer-sity of Oxford, Commonwealth Forestry Insti-tute, Fast Growing Timber Trees of the Low-land Tropics 4; 1968. 169 p.

3. Fernandez, Magan F. J. Anotaciones sobre el cul-tivo de1 Eucalyptus glob&us en 10s viveros de1litoral gallego. Madrid: Centro Forestal Re-gional de Lourizan, Instituto Forestal de Inves-tigaciones y Experiencias, Cbmunicacion 113;1971. 31 p.

4. Food and Agriculture Organization of the UnitedNations. Eucalypts for planting. Rome: FAOForestry Series 11; 1979. 677 p.

5. Lamb, A. F. A. Cedrelu odoratu. Oxford: Univer-sity of Oxford, Commonwealth Forestry Insti-tute. Fast Growing Timber Trees of the Low-land Tropics 2; 1968. 46 p,

6. Lamb, A. F. A. Gmelinu arboreu. Oxford: Univer-sity of Oxford, Commonwealth Forestry Insti-tute. Fast Growing Timber Trees of the Low-land Tropics 1; 1968. 31 p.

7. Lamb, A. F. A. Pinus curibueu, Vol. 1. Oxford:University of Oxford, Commonwealth ForestryInstitute. Fast Growing Timber Trees of theLowland Tropics 6; 1973. 254 p.

8. Lamb, A. F. A.; Ntima, 0. 0. Terminalia iuoren-sis. Oxford: University of Oxford, Common-wealth Forestry Institute. Fast Growing Tim-ber Trees of the Lowland Tropics 5; 1971.254 p.

9. Ntima, 0.0. The Aruucarius. Oxford: Universityof Oxford, Commonwealth Forestry Institute.Fast Growing Timber Trees of the LowlandTropics 3; 1968. 139 p.

10. Paul, Derek K. A handbook of nursery practicefor Pinus curibaeu var. hondurensis and other

132

conifers in West Malaysia, Malaysia UnitedNations Development Programme, Food andAgriculture Organization of the United Na-tions, FO:SF/MAL 12, Working Paper 19;Kuala Lampur: 1972. 139 p.

11. Webb, D. B.; Wood, P. J.; Smith, J. A guide toI1251 species selection for tropical and sub-tropical plantations. Oxford: University of Ox-ford, Commonwealth Forestry Institute. Tropi-cal Forestry Papers 15; 1981. 342 p.

12. Whitmore, T. C. A first look at Agathis. Oxford:University of Oxford, Commonwealth ForestryInstitute. Tropical Forestry Papers 11; 1977.54 p.

13. Wormald, T. J. Pinus put&a. Oxford: Universityof Oxford, Commonwealth Forestry Institute.Tropical Forestry Papers 7. 1975. 216 p.

LITERATURE CITED I

1. Ag Consultant and Fieldman. 1983 Weed controlmanual. Willoughby, OH: Meister Publ. Co.;1983. 298 p.

2. Cordell, C. E.; Kelly, W. D. Soil fumigation inSouthern United States forest tree nurseries. In:South, David B., ed. Proceedings, internationalsymposium on nursery management practicesfor the southern pines; 1985 August 4-9; Mont-gomery, AL. Auburn, AL: Auburn University,School of Forestry, Alabama Agricultural Ex-periment Station; 1985: 496-504.

3. Farm Chemicals Magazine. Farm chemicals hand-book ‘83. Willoughby, OH: Meister Publ. Co.;1983. (pagination varies).

4. Venator. C. R. The relationship between seedlingheight and date of germination in Pinus curibueavar. hondurensis. Turrialba. 23(4): 473-474;1973.

Appendix 12

Practical Guides for Using Herbicides and Pesticides

I. Herbicide InformationII. Pesticide Information

III. Procedures for Calculating Solution Concentrations

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I. Herbicide Information

GENERAL INFORMATION

When used properly, herbicides control weeds innurseries where hand weeding is too costly or imprac-tical. The objective is to eliminate competing vegeta-tion that stunts seedling tops and roots, causes un-even seedling growth, and decreases seedling survivalper unit area of nursery bed.

Weeds are usually classified as grasses, sedges, orbroadleaf plants that are annual or perennial in na-ture. Some weeds are local problems only, whereasothers occur across broad regions, even countries. Leftuncontrolled, a single weed species can destroy up to70 percent or more of plantable seedlings (5).

Certain termssare used repeatedly in herbicide useand weed control. Knowing them is essential to un-derstanding how herbicides work and why they mustalways be considered controlled substances. A list ofthese terms with their definitions is given below (3).Acid equivalent-That portion of a compound or for-

mulation that theoretically could be converted backto the corresponding acid.

Active ingredient-The chemical(s) in a formulatedproduct that is (are) principally responsible for thepesticide effects and that is (are) shown as activeingredient(s) on the label.

Adjuvants-Additional compounds added to pesti-cides to act as wetting or spreading agents, stickers,penetrants, emulsifiers, etc., to make them easier tohandle, mix, or apply.

Broadcast treatment-Applied over an entire area, byground or aerial means.

Carrier-A gas, liquid, or solid substance used to di-lute, propel, or suspend a pesticide during its appli-cation.

Concentration-The amount of active ingredient orpesticide equivalent in a quantity of diluent, ex-pressed as percent, lb/gal, ml/L, etc.

Defoliant-A pesticide used for the removal of un-wanted foliage without necessarily killing wholeplants.

Desiccant-A pesticide used for drying insects orplant leaves and stems.

Diluent-Any gas, liquid, or solid material used toreduce the concentration of an active ingredient ina formulation.

Dormancy-A state of inhibited plant or animalgrowth.

Emulsifiable concentrate-a pesticide mixture dis-solved in a liquid solvent. An emulsifier is includedso that the pesticide can be diluted with oil or waterand used.

Foliar application -Wetting of foliage with pesticide,usually to the point of runoff.

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Formulation-The mixture of active and inert ingre-dients in a pesticide. Some formulations are readyfor use; others must be diluted.

Frill treatment-Application of pesticide to nearlycontinuous cuts spaced around a tree at a conven-ient height.

Fumigant-A pesticide used in gaseous form.Fungicide-A pesticide for control of fungi.General-use pesticide-A pesticidal product that will

not cause unreasonable adverse effects on the envi-ronment when used as directed, and that may bepurchased and used by the general public.

Granule or granular -A dry formulation of pesticideand other components in discrete particles gener-ally less than 120 cubic millimeters in size.

Herbicide-A pesticide for control of unwanted vege-tation.

Insecticide-A pesticide for control of insects.Integrated pest management-A process in which all

aspects of a pest-host system are studied andweighed to provide the resource manager with in-formation for decision making. Integrated pestmanagement is, therefore, a part of forest or re-source management.

Label-The written, printed, or graphic matter on, orattached to,’ a pesticide container.

Notch or cup treatment -Application of pesticide tocuts spaced around a tree at a convenient height.

Noxious weed -A weed specified by law as being espe-cially undesirable, troublesome, and difficult tocontrol.

Oil-Aromatic or paraffinic oils used as diluents orcarriers.

Preemergence-Prior to emergence of the specifiedweed or planted crop.

Registered pesticide -A pesticide that has been regis-tered with the Environmental Protection Agency(EPA) under the Federal Insecticide, Fungicide,and Rodenticide Act, as amended.

Registration-The process whereby all pesticides areregistered by the Environmental Protection Agency(EPA) under authority of the Federal Insecticide,Fungicide, and Rodenticide Act, as amended. Allpesticide labels must have an EPA registrationnumber.

Release-The process of removing competing vegeta-tion that competes for soil moisture, nutrients, andlight with desirable vegetation.

Repellent-A pesticide used to keep animal pestsaway.

Restricted-use pesticide-A pesticide product for ap-plication only by certified applicators or personsunder their direct supervision.

Rodenticide-A pesticide used for rodent control.Seed protectant -A chemical applied to seeds before

planting to protect seeds and/or seedlings frompests.

Surfuctunt-A material that favors or improves theemulsifying, dispersing, spreading, wetting, orother surface-modifying properties of liquids.

Suspension -Finely divided solid particles dispersedin a solid, liquid, or gas.

Tree injection-Application of pesticide into the sap-wood of individual trees using tubular injectors.

Ultra low uolume-Applications of small amounts ofpesticide (0.47 to 0.94 liters or less per acre).

Volatility-The ability of a solid or liquid to evapo-rate quickly at ordinary temperatures when ex-posed to the air.

Wettable powder -A finely divided dry pesticide for-mulation that can be suspended readily in water.

Wetting agent -A chemical that helps a pesticidespread and coat (wet) a surface more evenly. It cutsdown on the amount of a spray that rolls off smoothor waxy leaves and helps sprays to spread out onhairy leaves. Detergents are sometimes used aswetting agents.

1. Atmospheric environment: Lower air tempera-tures, CO, levels, and barometric pressuresreduce herbicide effectiveness.

2. Soil temperuture: Higher temperatures usuallyaffect overall weed growth and metabolismfavorably, increasing herbicide uptake andtranslocation.

3. Water: Higher relative humidity and good soilmoisture (i.e., plant not under water stress)increase herbicide effectiveness.

4. Light: Changes in photoperiod, light-inducedchanges in leaf morphology, and photode-composition of herbicides affect herbicide ef-fectiveness.

5. Wind: Physical plant damage by wind and in-creased transpiration and water stresscaused by wind usually increase herbicideuptake.

6. Microenvironment: Localized changes in soil pHvalue, microflora, and fauna affect plantgrowth and herbicide effectiveness, nega-tively or positively, depending on the herbi-cide used and plant grown.

PLANT FACTORS AFFECTING TOXICITYHERBICIDE APPLICATION

Herbicides are selective or nonselective. Selectiveproducts are more toxic to some plants than others;nonselective products kill a broad spectrum of weeds.Because seedlings are plants; weed control usuallycenters on selective herbicides. Four major plant fac-tors affecting selectivity differences (1) are:

1. Morphological differences : Factors such as plantsize and shape, leaf shape and size, growthstage, presence or absence of waxy and hairysubstances, and location of roots close to orwell beneath the surface affect contact andabsorption of herbicides.

2. Physiological differences : Internal processes de-termine whether introduced herbicides arebroken down into harmless byproducts orblock key processes that eventually causeplant death.

. 3. Absorption differences : A combination of mor-phological and physiological differences al-low greater or lesser uptake of herbicide byplant roots and shoots.

4. Trunslocution differences : Physiological factorsdetermine whether herbicides are trans-ported with phloem or xylem substances.

ENVIRONMENTAL FACTORS ANDTOXICITY

In addition to plant factors, environmental factorsthat influence herbicide toxicity (4) are:

Herbicides are seldom sold as pure chemicals. Theyare formulations of an active chemical plus variousadditives that allow uniform application. Major herbi-cide types (4) are:

1. Sprays :(a) Solutions: a homogeneous mixture of two or

more substances.(b) Emulsions: one liquid dispersed in another

with each maintaining its separate indentityiemulsifying agents are materials sold to helpformulate emulsions.

(c) Wettable powders: very finely ground solidparticles that are suspended or dispersed in acarrier such as water or oil and sprayed onweeds.

2. Granules: Chemicals usually mixed with carri-ers such as sand and vermiculite and spread by broad-casting over weeds.

3. Dusts: Used for insecticides and fungicides butnot usually for herbicides because of drift problems.

APPLICATION EQUIPMENT

Sprayers suitable for herbicide application rangefrom small back-mounted tanks (7 to 15 liters) totractor-drawn boom rigs (200 to 2,000 liters) capableof covering several hectares. For nonselective herbi-cides, various “rope wick” or “wiper” applicators treatundesirable weeds but protect small seedlings. Broad-

135

cast or hand “cyclone” spreaders and tractor rigs arebest for granular herbicides. Properly calibrated andcleaned equipment is essential for large and smallspraying jobs (fig. 16-3B).

HERBICIDE CLASSIFICATION

The herbicide classifications are technical or non-technical. Technical classifications use chemicalstructures and major functional groups at the highestlevel of categorization; however, such systems arewithout standardization (1). Table A12-1 lists onetechnical classification, with 16 major categories andspecific products under each group.

A more practical, non-technical classification fornursery herbicides is that based on when herbicidesare applied relative to seedling germination:

1. Preplant : soil incorporated, applied before seed-ing is .done.

2. Preemergence: applied after seeding but beforegerminants emerge from seedbeds.

3. Postemergence: applied after seeding and aftergerminants have emerged fromseedbeds.

In all instances it is easier to control germinatingweed seeds than to control already established weedswith contact herbicides.

Many herbicides have the same major chemicalagent but are sold under different trade names,mainly because of different carrier compounds. Someproducts have been around a long time (e.g., atrazine),others less so (e.g., Goal). Lists go out of date quicklybecause of changes in product formulation. Keepingthis in mind, table A12-2 lists major preplant, pre-emergence, and postemergence herbicides now usedin pine nurseries in the Southern United States andVenezuela.

Table Ala-l.-Technical classification herbicide groups’

Herbicide group

1. Phenoxy compounds2. Benzoic acids3 . P i c loram4. Benzonitri les5 . B ipyr id in ium sa l t s6 . A m i t r o l e7. Aliphatic acids8. Subst i tuted phenols9 . Maleic hydrazide

10. Subst i tuted ureas11. Triazines12 . Diaz ines13. Amides14. Carbamates15. Trifluralin16 . Xylene

Qource: (Il.

Specific herbicide examples

2,4-D; 2,4,5-T; MCPA; silvexchloramben (Amiben)Amdonbromoxynil; ioxynilparaquat; diquatamerol; cytroldalapon; TCAdinoseb; DNBPM Hchloroxuron; diuron, linuronsimazine, atrazine; prometrynpyrazondiphenamid; propanilchlorpropham; CDECIpersan, Treflandimethyl benzene

Table Ala-2.-Preplant incorporated (PPI), preemergence (PRE),and postemergence (POST) herbicides used in theSouthern United States and Venezuela for con-trolling weeds in pine nurseries1

U.S.A. Venezuela

PPI

EptamEradicaneSutanVernam

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

PRE

AatrexLassoSencorMilogardPrincepSurfIanTref lanCaparolEnideDestunD u a lDevrinolModownCoalRonstar

Sencorl i n u r o nPatoranDactha lProwl

POST

RoundupVelparPoastAttac

D i u r o natrazineSencorl i n u r o nMineral spirits

%urces: (41, (2).

Whenever possible, new products must be tested inreplicated nursery trials to detect selectivity traits forforest seedlings and local weeds. For example, oneexperiment with P. caribaea var. hondurensis trans-plants showed that 26-day survivals were better whenseveral herbicides were applied to beds 48 to 72 hoursbefore rather than 24 hours before transplanting (2 1.

SPOTTING HERBICIDE PROBLEMS

Failure to carefully follow instructions on herbicideproduct labels inevitably causes problems. Some ofthese and their probable causes (3) are:

1. Poor weed control: This problem is caused byfailure to use selective herbicides for certainweeds and failure to apply herbicides at cor-rect rates, right time, or in the best mannerpossible.

2. Seedling injury : Herbicides are often blamed forinjuries that are also caused by insects, dis-eases, wind, overwatering, nutrient defi-ciencies, and abnormal weather conditions.

136

Practices involving herbicides that causeseedling injury are:(a) Using a herbicide not labeled for a par-

ticular tree species;(b) Failure to clean spray equipment thor-

oughly, resulting in leftover herbicidebeing applied to susceptible seedlings;

(4 Planting susceptible seedlings on landtreated with herbicide the precedingyear;

(d) Using application rates excessive tothose recommended;

(e) Improper timing of herbicide applica-tion; and

(0 Drift to susceptible seedlings from wind,washing and cleaning equipment, andsoil leaching.

To minimize herbicide problems, always read andfollow label directions carefully, using only suggestedapplication rates, and consider herbicides a8 toxic sub-stances that must always be used under controlled con-ditions.

When any chemical application equipment is used,be certain that spray tanks are thoroughly cleanedbefore as well as after use. Follow carefully all direc-tions for mixing, applying, and using materials.Empty bags should be burned. All chemicals shouldbe kept in secure storage to avoid accidental injury orcontamination of areas surrounding nursery beds andbuildings, particularly when nursery facilities are lo-cated in watersheds from which potable water is ob-tained.

II. Pesticide Information

The accompanying list is a generic one becausemost items are sold under trade names. Packagelabels must be checked to see if they contain recom-mended chemicals. The list contains only a very smallnumber of the control materials available, but it in-cludes those most commonly sold in the tropics.

INSECTICIDES

Malathion -widely available, sometimes odorous;useful to control aphids, scales, mealybugs, and somechewing insects.

Metuldehyde-useful for control of snails and slugs.Nicotine sulfate-an old, reputable, and effective

control for aphids and other sucking insects.Ethion-useful in controlling leafhoppers, mites,

and thrips.Rotenone-a plant material used both as a contact

and 8tomach poison; it has no toxicity to man.Curbaryl-a broad spectrum insecticide; it is ex-

tremely toxic to bee populations and should beavoided where production hives are located.

MITICIDES

Suprucide 2E-long shelf life if stored in cool, dryplace.

Ouex-extremely effective, but use requires specialcare; read label instructions carefully.

Chlorobenzilate -used with good results.

FUNGICIDES

Methyl thiophanate-effective for control of soilfungi; used as a soil drench.

Bordeam mixture-probably the most’ practicalfungicide available. For very small amounts, dissolve0.1 liter of copper sulfate in 3.8 liters of water byputting the crystals in a cloth bag and hanging themat the top of water in a bucket. Then add 7.6 liters ofwater and 0.7 liter hydrated lime solution to make11.6 liters of 11.6 Bordeaux mix. Use immediatelybecause effectiveness is lost if the mixture stands toolong. Adding a little soap to the final solution makesit stick and spread better.

Formaldehyde or formalin-can be used on bareground before planting; it is texic to plants yet excel-lent as a preplanting drench to control soil fungi. Itsfumes are toxic to people.

Lime sulfur-used to control mildews; it is also amiticide.

Meneb-useful in controlling spot diseases, i.e.,leaf spot fungi.

SOIL FUMIGANTS

Ethylene dibromide- an effective soil fumigantthat controls soil insects and nematodes. Soil treatedwith this material cannot be planted for at least 3weeks because it is very toxic to plants. It is also verytoxic to humans. It is sold under a number of commer-cial names.

Nicotine -sold under several trade names; it is safeto use and effective for soil insects.

137

SPREADERS

Substances to increase the adherence of sprays toplants. A few shavings of ordinary soap or a smallamount of detergent will serve the purpose.

SEED TREATMENTS

Thirum-a wettable powder used as a slurry to coatseeds for protection against damping-off, seed decay,seedling blights, and rodents (table A12-3); it is sug-gested for conifer seeds.

PREPLANTING BED TREATMENT

Captan-applied to nursery beds before planting tocontrol damping-off; it is worked into the top 8 to 10cm of soil

Table AlB-3.-Listing of bird and rodent repellents and stickersused for forest tree seeds in Latin America

C o m m o nname

Repel lents

Birds Rodents

Chemical Common Chemicalname name name

Anthraquinone 9, lo-Anthraquinone . . . . . . . . . . . . . . . . . . . . .Avitrol I-Aminopyridine Thiraml B i s

(dimethyl-thio-carbamoyl)disulfide

DRC-1339 3-chloro-p-teluidine Ziramr Bishydrochloride (dimethyl

dithio-carbamato)zinc

Stickers

Ag-them . . . . . . . . . . ...*..... . . . . . . . . . . . . . . . . . . . . .activator

Tr i ton . . . . . . . . . . . . . . . ...* . . . . . . . . . . . . . . . . . . . . .

lProducts registered in the United States by U.S. Environmen-tal Protection Agency as fungicides only.

III. Procedures for Calculating Solution Concentrations

Often, the nursery technician needs to dilute or pre-pare a specific concentration of an insecticide, fertil-izer, or other chemical. The best way to explain how aspecific concentration can be derived from anotherconcentration is to provide an example.

Assume a typical dilution problem where one has150 liters of an insecticide, previously diluted to 15percent strength, and needs 435 liters of the insecti-cide with a final dilution of 4.5 percent. The problemis: How much of the 150 liters must be used to prepare435 liters with 4.5-percent insecticide? The followingformula can be used to determine the correct dilution:

Cl VlClVl=C2Vz o r G=F, o r

Where

Ci = concentration of first solution,Cz = concentration of second solution,VI = volume of first solution,

andV2 = volume of second solution.

Then

(15%) (VI) = (435 liters)(4.5%)

or solving for V,,

VI = 120 liters.

Thus, 120 liters of the 15-percent strength insecti-cide combined with 315 liters of solvent (generallywater) will yield 435 liters with a 4.5-percent concen-tration of the pesticide.

LITERATURE CITED

1. Audus, L. J., ed. Herbicides-physiology, bio-chemistry, ecology. New York: AcademicPress; 1976. 564 p. Vol. 2.

2. Fernandez, Victor; Arrieche, Rafael. Ensayos deherbicidas de uso pre-emergente para controlde malezas en viveros de Pinus curibueu var.curibueu . Venezuela Forestal. 6: 38-64; 1982.

3. Hamel, Dennis R. Forest management chemi-cals. Agric. Handb. 585. Washington, DC: U.S.Department of Agriculture, Forest Service;1983.645 p.

4. South, David. Weed control. In: Lantz, Clark W.,ed. and camp. Southern pine nursery hand-book. Atlanta, GA: U.S. Department of Agri-culture, Forest Service, Southern Region;1984: 15-1 to 15-23.

5. South, David B; Gjerstad, Dean H.; White, TerryE. Effects of bermuda-grass on production ofloblolly pine seedlings in a Louisiana nursery.Tree Planters’ Notes. 29(4): 20; 1978.

138

Appendix 13

Guides for Applying Fertilizers and Preparing Compost

I. Important Fertilizer FactsII. Procedures for Building a Compost Pile

139

I. Important Fertilizer Facts

GENERAL

The guides provided here are applicable to tradi-tional and large-scale operations using bulk fertiliz-ers. Greenhouse practices for using soluble fertilizerswith irrigation water are more complex. An excellentreference on mineral nutrition in greenhouses is thatof Tinus and McDonald (4). Since the guides hereinare general, caution is needed in their interpretationbecause soils or local site conditions probably exist forwhich some guides are not applicable.

DETERMINING FERTILIZER NEEDS

Whenever possible, nursery field test results arecompared with known ranges in nutrient levels forvarious kinds of nursery soils (table 13-4). Wherelevels are unknown, fertilizer needs are approximatedby comparing field test data with “benchmark” low,medium, and high field levels applicable to a widevariety of crops (table A13-1) (2).

APPLICATION METHODS

There are four ways of applying fertilizers. Eachhas certain advantages and disadvantages, dependingon type of fertilizer (2):

1. Broadcasting: uniform spreading of fertilizerover the soil and working it in by machine orwith hand implements before seeding. Thismethod gives best distribution of fertilizersto root systems, has little danger of “burn-ing” seedling roots, and is not labor inten-

Table A13-L-General field soil fertility levels for agriculturalcrops l

Element Low Medium High_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Kg/ha -________--______---------

N 35-55 60-95 100+pzo5 25-35 40-60 70+K20 30-40 50-70 80+

‘Knowing these “benchmark” field soil fertility levels and thefact that a crop of pine seedlings on sandy soils requires about 1,100kg/ha of 10-10-10 and 300 kg/ha of ammonium nitrate (2), man-agers can make fertilizer estimates for their nurseries. With expe-rience and record keeping over several years, managers will deter-mine whether benchmark field fertility guides are accurate. Forinterpreting long-term fertility data, managers should determine anursery’s annual cost of fertilizer, kinds and timing of applications,whether limited capital restricted fertilizer use in any years, andwhether fertilizer shortages in any years caused substituting usualproducts for others.

140

sive. Disadvantages that usually outweighthe advantages are: tie up of soil P and K(i.e., makes them less available), ineffectiveat low application rates, fertilization of bothweeds and seedlings, and difficulty in get-ting equipment for completely uniform ap-plication and incorporation.

2. Localized placement (banding) : placing fertiliz-ers in bands to the side (5 to 8 cm) or under(6 to 10 cm) seeded rows. When NPK or Nand K fertilizers are placed under seededrow and trench irrigation is used, placementmust be under maximum water height; ifnot, N and K salts move upward by capillaryaction as soil dries and burn seedlingroots-P does not burn. Other disadvan-tages are: requires special applicationequipment, cannot be done manually, andfertilizers must be applied before seedsgerminate. Generally, advantages far out-weigh disadvantages: maximum efficiencyfor small or medium application rates, mini-mal tieup of P and K, less feeding of weedsthan in broadcasting, and best method forseedlings with small root systems.

3. Foliar application: applying nutrients in solu-tion to seedling foliage. The method is suitedfor correcting micronutrient deficiencies butnot for applying general NPK fertilizers.Over-fertilizing with NPK can cause foliageburn if excess amounts are not washed off.Most foliar fertilizer products are very ex-pensive; discriminate use is the key to effec-tive use.

4. Irrigation water applications: applying solublefertilizers in overhead or trench systems.Methods require special attention, particu-larly in dry climates where water containshigh soluble salts and soil water evapora-tion is great. Under these conditions, irriga-tion fertilizer application may be quitewasteful; burning of roots is also a problemwhen salts accumulate in the root zone.

APPLICATION

General Considerations

For best results, NP and NPK fertilizers are appliedat or close to planting time. To reduce N and K leach-ing, only one-third to one-half of the amounts neededare applied initially. The remaining amounts are applied about one-third and one-half of the way throughthe expected seedling rotation.

PIncomont is at least 7.5 to 10 cm deep and 5 to 7.5cm to the side of seedling rows. Side placement pre-vents burning by K and N carried upward in soil cap-illary water.

Specific Considerations

To prevent volatilization, urea-N is always incorpo-rated in the soil, never broadcast on the surface. Be-cause N is mobile, placement does not have to be asdeep as for P. Timing of N application is especiallycritical when cover crops are incorporated; high C/Nratios will tie up N in decomposition unless fertilizerN is added. If N-fixing seedlings are grown, overall Nneeds are much less for any nursery soil.

Because P is easily tied up in the soil, it is alwaysincorporated deeply, never broadcast. Major P needsare for good root growth after sowing; later applica-tions are wasteful unless specific P deficiencies arefound. Adding N with P aids P uptake by seedlings.

Leaching losses of K are between those of N and P.Efficient applications are those incorporating K at ornear sowing. Crop residues are usually high in K.

Sulfur is mobile and readily leached. The majorS-bearing fertilizer components used will determineapplication method and placement. Micronutrientavailability is very strongly related to soil acidity.Beyond pH value 6.8, availability of most micronutri-ents decreases (fig. 13-3).

Effects of Adding Excess Nutrients

Beyond certain concentrations, excess nutrients donothing to stimulate plant growth. In some cases, ex-cess nutrients actually limit plant growth, usuallybecause of interaction effects (1) such as:l excess K relative to Ca and Mg causing Ca and Mg

deficiencies;. excess P tying-up Fe and Zn and creating deficien-

cies when they are at borderline soil levels;l excess Ca relative to Mg possibly creating Mg de&

ciency ;l overliming causing micronutrient deficiencies; andl excess soluble Cu and Mn causing Fe deficiencies

and vice-versa.

Fertilizer Burn

Excess fertilizer salts in the soil inhibit absorptionof other nutrients and cause physical burning (i.e.,osmotic desiccation) or death of root tissue when con-centrations are very high. When symptoms (leaf orroot tips turning brown and drying; visible salts onleaf surfaces) are caught in time, applying excess, un-fertilized, irrigation water will wash away these salts.Not all fertilizers have the same burn potential (tableA13-2). When in doubt, keep all fertilizers away fromdirect contact with seedling roots and foliage tissue.

Table Al3-2.-Relative burn potential of different fertilizers1

Fertilizer Formula Salt index per9 kg of plant nutrients

Sodium nitratePotassium nitrateAmmonium su l fa teAmmonium ni trateMono-ammonium phosphatePotass ium magnes ium su l fa tePotassium chlorideUrea 2

Di-ammonium phosphate2Potassium sulfateSingle superphosphateTriple super-phosphateGypsum

1 6 - O - O14-O-4621-o-o33-o-o11-48-O

o-o-22O-0-60

45-o-o18-46-Oo-o-54O-20-00-48-O

6.05.33.22.92.51.971.931.61.60 .650.40.20.25

GREATEST

vLEAST

*Source: (2 ).2Urea and DAP may cause more injury than ammonium sulfate

because they release free ammonia.

Fertilizer Mixing Guides and Dosages

If lime is mixed with urea or ammonium-N fertiliz-ers, ammonia gas is formed. Similarly, mixing limewith ammonium phosphates, super phosphates, orany fertilizer containing P will make most or all of theP insoluble. Other fertilizer mixing incompatibilitiesare shown in figure A13-1.

POTASSIUMCHLORIDE

POTAsSluYSULFA1 E

AMMONIUMSULFATE

SODIUM NITRATE L IPOTASSIUM NITRATE

CALCIUM NITRATE

UREA

SINQLE R TRIPLESUPERPHOSPHATE

MONO (L DI-AMYONIUPHOSPHATE

LIME

-l-m-

0-

cl

cl FERTILIZERS THAT CAN BE MIXED.

E lFERTILIZERS THAT CAN BE MIXED ONLYSMORTLY BEFORE USE.

ElFERTILIZERS THAT CANNOT BE MIXEDFOR CHEMICAL REASONS.

Figure A13-L-Fertilizer compatibilities. Taken from (2).

For small nurseries, application rates are some- raising their unit weight. If a fertilizer is suspected oftimes best expressed as grams/length of row or grams/ being “wet”, a sample is placed in the sun for a fewplant instead of kilograms/hectare. Thus, knowing hours or dried in an oven at 70°C for 2 to 3 hours. Thedosages in terms of tablespoons, handfuls, or other measuring device should hold at least 100 cc. Dryvolume measurements is helpful. Converting applica- weight is then recorded for the amount in the cylin-tion rates from a weight to a volume basis is done by der. Where scales are scarce, one may possibly be ob-determining the density of a particular fertilizer with tained from a local pharmacist. With a scale anda scale and calibrated measuring device such as a measuring container (graduated cylinder), a simplegraduated cylinder. “Relative density” is used be- table can be developed that gives the relative densi-cause stored, uncovered fertilizers attract water, ties of fertilizers (1).

II. Procedures For Building A Compost Pile

Compost is made by letting alternate layers of plantand animal wastes decompose in a pile or pit. The endproduct is a dark, earthy looking humus soil im-prover. The first step in making a compost pile is tolay out a 2- by 2-m base of organic (high carbon) ma-terial, e.g., leaves, rice hulls, sugarcane waste, andcrop stubble. Height of the first layer should be about20 cm. The next layer is a lo-cm covering of high Nmaterial, usually fresh animal manure (table 13-10);do not use composted manure. The nitrogenous layerprovides N for fungi and bacteria to break down theorganic layer. Alternate carbon and nitrogen layersare added until the pile is about 1.5 m high. The top-most layer is a high N one (I).

The final compost should have a carbon to nitrogenratio of between 2O:l and 3O:l (table A13-3). Strawand wood residues usually have too much C comparedto N; microbes cannot break down the material. Im-mature green vegetation has more N than needed,and microbes turn the excess into ammonia gas,which is lost.

As the pile is constructed, each layer is moistenedslightly. To avoid washing layers away, water should

Table A13-3.-Carbon-nitrogen ratios of various organic materials1

Material C:N Ratio

Fresh grass clippings 12Fresh animal manure 15-20Clover residues 23Green rye 3 6Leaves 40-80Sugarcane trash 5 0Straw manure 250Corn stover 6 0Straw 50-130Sawdust (rotted) 2 1 0Sawdust (fresh) 400-500

Bource: (2 ).

be applied with a fine spray nozzle. The mix shouldfeel wet but not soggy.

After the final layer is added, a large depression ismade in the center. The depression catches rain orapplied water to maintain high moisture (about 50percent) in the pile. Often the pile is covered with aE-cm layer of leaves, burlap, or other material toprotect it from the wind. It also helps conserve heat,generated by the micro-organisms, that is necessaryto kill weed seeds and pest organisms in the pile. Alarge pile at least 1.5 m high by 2 m wide at the baseis self-insulating; any length can be used.

A final but important step is taking daily tempera-ture readings at the center and edges of the compostpile over the first 3 weeks. If temperatures >6O”C aremeasured, internal heat of the compost pile has prob-ably killed decomposing micro-organisms (3 >. Whenthis occurs, the compost pile has “stuck” and must berestored before further decomposition continues.Restoring a stuck pile. involves complete turning todissipate heat and provide aeration and reintroducinghigh N animal-waste layers within the pile.

Since microbes need air, maintaining aeration inthe pile is critical for completing the cornposting proc-ess. The more often a pile is turned, the faster com-posting is completed. Turning a pile one or two timesa week is ideal, but turning it every other week isprobably more realistic unless a tractor-mountedbucket replaces hand labor in turning. If the pitmethod is used, two pits are built; turning involvestransferring the pile from the full to empty pit.

An improperly composted pile will not ferment com-pletely, and pathogenic organisms or viable weedseeds may remain. The problem is corrected by recom-posting the material. Contamination with weed seedis controlled by using seed-free vegetative material.Length of time for cornposting is 2 to 6 months. There-fore, cornposting must be started several months inadvance of seedling production runs. To test for weedcontamination, small quantities of compost are used

142

ta ~mminste tree seed,s: if weed seeds also germinate,the material must be recomposted.

Compost is expensive when transporting compost-ing materials is a major cost. Locating a nursery nearan animal husbandry complex will reduce transporta-tion costs and will provide a ready supply of manure.Because of approximately equal elemental composi-tion in animal manures (table 13-101, the authors donot recommend one over another; horse manure hasperhaps more fiber content than other manures.

Physical location of a compost pile or pit should begiven special attention because the very nature of thematerials used attracts flies, rodents, etc. Compostpits should be located downwind and far away fromthe main nursery work area. Although some compostpits are left in the open, placing them under a shelter-house, having a concrete floor and enclosed, rodent-proof fence around it, is preferred. Also, with a con-crete floor, K- and NOB-rich leachates can be collectedand recycled.

LITERATURE CITED

1. Bunt, A. C. Modern potting compost: a manual onthe preparation and use of growing media for potplants. University Park, PA: The PennsylvaniaState University Press; 1976. 277 p.

2. Leonard, Dave. Soils, crops & fertilizer use or awhat, how, and why guide. 3rd ed. Reprint 128;Washington, DC: Peace Corps, Information Col-lection and Exchange; 1980. 162 p.

3. Poincelot, Raymond P. The biochemistry andmethodology of cornposting. New Haven, CT:Connecticut Agricultural Experiment StationBull. 754; 1975. 18 p.

4. Tinus, Richard W.; McDonald, Stephen E. How togrow tree seedlings in containers in green-houses. Gen. TechRep. RM-60. Ft. Collins, CO:U.S. Department of Agriculture, Forest Service,Rocky Mountain Forest and Range ExperimentStation; 1979. 266 p.

143

Appendix 15

Specialized Facts for Container Stock Production

I. List of Container ManufacturersII. Five Types of Containers that are Useful in Tropical Countries

III. Suppliers of Commercial Potting MixesIV. Split-Level Nursery Operations for Producing Container Stock

145

I. List of Container Manufacturers1

SupplierCommon name

of containerContainermaterial

Biodegradableproperties

Rootegress

Ameripak806 Central Ave.P.O. Box 8686Middletown, OH 45042-8686

Capilano Plastics Co. Ltd.1081 Cliveden Ave.Annacis IslandNew Westminister, BCCANADA V3M 5Vl

Castle and CookeTechniculture, Inc.

P.O. Box 1759Salinas, CA 93902

Colorado Hydro Inc.5555 Ute HighwayLongmont, CO 80501

Colorado State NurseryFoothills CampusColorado State UniversityFort Collins, CO 80523

GASPRO, Inc.2305 Kamehameha Hwy.Honolulu, HI 96819

HGP Inc.761 Kanoelehua Ave.Hilo, HI 96720

Hakmet Ltd.P.O. Box 248Dorion, QuebecCANADA J7V 755

Jiffy Products of America1400 Harvester RoadP.O. Box 338West Chicago, IL 60185

Lannen Inc.2646 Palma DriveSuite 140Ventura, CA 93003

Mansonville Plastics Ltd.19402 - 56th Ave.Surrey, BCCANADA V3S 6K4

J. M. McConkey Co., Inc.P.O. Box 309Sumner, WA 98390

Plant-a-Plug SystemsP.O. Box 1953Pine Bluff, AR 71613

146

Ameripak Polystyrene N o N o

Capilano Seedling Tray High densitypolyethylene

No No

Seedling tray; plugs Expanded polystyrene;polyurethane foam

No NoN o N o

No

No (reusable)

Colorado Styroblock

Colorado Styroblock

High-impactpolystyrene

Polystyrene foam

No

No

No

Yes

Yes

Hawaii Dibble Tube

Polybag

Paperpot

Polyethylene No (reusable)

Yes

Yes

Perforated plastic bag

Specially-treated paper

Jiffy pots and peat pellets Molded peat moss Yes Yes

Paperpot

Styrofoam blocks

Specially-treated paper Yes Yes

N oPolystryene foam No

DEEPOT; seedling trays

Styrofoam blocks

High densitypolyethylene

Polystyrene foam

No

No (reusable)

No

N o

I. Liet of Container Manufacturers-Continued.

Multipot High densitypolyethylene

N o N o

Styroblock Polystyrene foam No (reusable)

Todd@ Planter Flat Expanded polystyrene No (reusable)

Supplier

Ray Leach Cone-tainer Nursery1500 N. Maple St.Canby, OR 97013

Common nameof container

FUL Single Cell

Containermaterial

High densitypolyethylene

Biodegradable Rootproperties egress

N o N o

Sauze Technical Products Corp.345 Cornelia St.Plattsburgh, NY 12901

Silvaseed CompanyP.O. Box 118Roy, WA 98580

N o

Speedling, Inc.Old Highway 4’1 SP.O. Box 238Sun City, FL 34268

No

Spencer-Lemaire Industries, Ltd.11413 - 120 st.Edmonton, AlbertaCANADA T5G 2Y3

S/L Rootrainer Polystyrene No (perhaps reusable) N o

Treepot Enterprises12922 Harbor Blvd.Suite 678Garden Grove, CA 92640

Treepots; Styrofoamblocks

Polystyrene N o N o

Tubepack402 East 900 SouthSuite 2Salt Lake City, UT 84111

Tubepack Polystyrene No (perhaps reusable) N o

Western Pulp Products Co.Box 968Corvallis, OR 97331

Fiber pot Molded wood pulp Yes No (butpenetratepot)

‘Adapted from Tinus and McDonald, 1979, and information supplied by Dr. Thomas D. Landis, Region 6, Portland, OR.

1 4 7

II. Five Types of Containers that are Useful in Tropical Countries

ROOTRAINERS

This. container was originally called the Book-Planter (fig. 15-6). A new name was adopted after adesign change placed grooves along its entire lengthto eliminate root spiraling. The basic unit is a moldedcellulose acetate sheet that folds (as one closes a book)to rectangular, tapered cavities; a single large hole atthe bottom allows water drainage. Several cavitysizes are available, as are high-impact styrene trays,each holding 32 seedlings on elevated runners thatallow root egress and promote air-pruning of roots.Rootrainers can be reused once or perhaps twice, de-pending on the handling care they receive and theamount of direct sunlight, which photochemicallybreaks down the container walls.

Characteristics of this and similar containers are:

Advantages

1. Root development can be checked anytime with.out destroying roots or seedlings.

2. Ease of handling, since seedlings are carried tothe field in the containers.

3. Plugs are quickly extracted.4. Containers can be saved or thrown away, as de-

sired.5. If containers are not reused, there is no messy

cleaning.6. Mycorrhizal inoculum can be added directly to

roots at any time.

Disadvantages

1. Extra trays are required for handling and ship-ping.

2. Containers require assembly before filling withmedium and seeds.

3. Blank cavities must be reseeded or filled withtransplants.

4. If reused, cleaning and reassembling are laborand time consuming.

Outplanting performance of southern pineseedlings grown in Rootrainers has been similar tothe performance of those grown in Styroblock contain-ers.

RIGID POLYETHYLENE TUBES

Several rigid design containers are available, theLeach Cone-tainer being the most popular (fig. 15-5).Construction is injection-molded polyethylene, gener-ally reproducible by a local plastics forming industry.

Almost any diameter and length combinations arepossible. Tubes formed with internal ridges that pre-vent root spiraling are preferred over those withoutridges. Cone-tainer tubes or cells can be placed inracks with holes specially molded to hold them up-right. Polyethylene tubes produced for the tropicsshould be treated to resist greater ultraviolet radia-tion that causes untreated plastic to become brittle.

Other characteristics of rigid tubes are:

Advantages

1. Special racks allow easy handling of individualtubes and units of 100 or more.

2. Blank cells are easily replaced.3. Wider spacing is obtained by removing every

other cell.4. There is no root penetration between adjacent

cells.5. Seedlings are easily removed, culled, and graded

into equal heights before being sent to the field.6. Cells are reused for other seedling crops.

Disadvantages

1. Each cell must be handled individually for nor-mal use and recycling.

2. Extracting seedlings is a nuisance, in the nurs-ery or in the field; knocking or kneading of pliablecells is often needed for lifting.

3. If seedlings are removed from cells at the nurs-ery, extra packaging is needed to prevent drying ofroots and plug breakage.

4. Recycling the cells is labor and time consuming.

JAPANESE PAPERPOTS

Japanese paperpot systems are used widely in tem-perate zones, particularly for large-scale conifer pro-duction in Finland. Paperpots come in sets of 39 to1,400 units; each unit is bottomless and hexagon-shaped. For production runs of 1 to 2 millionseedlings, capital outlay is small and hand labor isadequate for filling and handling. For production runsas large as 10 million seedlings or more, equipmentfor complete mechanization should be purchased.

Paper-pot systems use glued bio-degradable paper.Sets are shipped as flat packages that expand into anupright honeycomb for filling in special trays. Tubesare joined by water-soluble glue, allowing separationat planting. The paper itself has plastic fibers andchemicals to increase container durability. A largevariety of diameters and lengths are available. Paper-

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pots are one of the few containers for which a completeline of handling, tilling, sowing, and planting equip-ment can be purchased. Six people can fill and seed upto 2 million pots per day.

Characteristics of paperpots are:

Advantages

1. Connected tubes are easily separated for plant-ing.

2. There is a wide range in size and number oftubes in unit packages, allowing wide choice of con-tainer volume.

3. Seedlings are carried to the field in the pots;thus, the root systems are protected from damage anddrying.

Disadvantages

1. Roots frequently penetrate adjoining tubes,making separation at planting difficult.

2. Tube paper can break down too soon, makinghandling and transporting dificult.

3. Paper degrades slowly in the field, slowing rootcontact with soil around planted tubes.

Overall, timing of lifting is critical for paperpots toprevent overdevelopment of root systems in the nurs-ery and break down of pots. Southern pine seedlingsgrown in paper-pots have generally had lower fieldsurvival and slower growth after outplanting thanseedlings grown in other containers (1).

STYROBLOCKS

The original container was made of molded styro-foam, with 80,135,160,192, or 240 cavities per blockor flat. Cavity volumes range from 40 to 125 cm3 anddepths from 10 to 20 cm. Interior surfaces of individ-ual cavities have a special glaze that protects againstroot penetration. Internal ribs orient root growthdownward and prevent spiraling. Runners on blockbottoms elevate them and promote air-pruning. Somemodels have “fences” around the top edges to preventwater runoff (fig. 15-4).

The SO-cavity block may be more suitable for thetropics where large seedlings are needed. Venator andRodriguez (3) recommended that pine seedlings begrown in low density blocks; however, Walters (4)found that higher density, 192-cavity blocks were ad-equate for producing large hardwood seedlings inHawaii. Styroblocks are expensive, but if the blockscan be reused two to three times as claimed by themanufacturer, unit seedling cost will be substantiallylower. Blocks are reusable until glaze coating on theinner surfaces is worn away by microbial activity orweathering. Seedling roots tend to grow into Styro-blocks without the glaze coating, and it is impossible

to remove seedlings without stripping roots. Theglazed surface can be protected by washing blocksimmediately after extracting seedlings and storingthe blocks under shade.

Equipment to fully mechanize Styroblock produc-tion systems is available. Simple, low-cost flat fillers,seeders, grit loaders, etc., are available that allowworkers to fill and direct seeds up to 300,000 cavitiesper manday of work.

An older product, Todd Planter Flats (fig. l&2), isalso made from Styrofoam and is now adapted forforestry as well as vegetable nurseries (I ). Cavityopenings in this container are square at the top andtaper to a small hole at the bottom.

Characteristics of Styroblocks and similar contain-ers are:

Advantages

1 . Cells are unitized in rigid but lightweight blocksthat are easily transported to remote planting sites,even when filled with seedlings.

2. Block material insulates seedlings from temper-ature extremes.

3. Blocks can be reused if handled, cleaned, andstored properly, reducing unit seedling costs over longperiods.

4. Glaze coating prevents root penetration of adja-cent cells and aids in lifting seedlings out of blocks.

Disadvantages

1. Empty cells must be reseeded or transplanted.2. Difficulties in seedling extraction will occur if

pot mix and moisture are not well controlled and if theglaze deteriorates.

3. Damage to a block beyond a certain amountmeans losing the entire block, even though some cellsare intact.

4. Recycling is labor and time consuming.Styroblock-produced seedlings usually grow better

under stress conditions than do those grown in paper-pots and other tubes. Outplanting performance ofseedlings from Todd Planter Flats may even surpassthat of seedlings from Styroblocks. This is presumablyso because the strongly tapered configuration of theplug promotes rapid root egress once plugs come incontact with surrounding soil (1).

POLYPOTS

These are rectangular containers, smaller versionsof the familiar paper milk cartons, manufactured bylaminating polyethylene onto both sides of cardboard.Drainage holes are punched before Polypots are cut tosize. Their major drawback is that they must be hand-folded and placed in trays before being filled. If lami-

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nating is adequate and handling of individual pots isminimal, Polypots last 12 to 14 months in nurseriesbefore disintegrating. There is no available equip-ment for mechanized filling and seeding of these pots.However, a good machinist should be able to constructsatisfactory equipment cheaply with local materials.

.Overall characteristics of Polypots are similar tothose of Japanese paperpots. Other features are:

Advantages

1 . Most countries have local capability to manufac-ture Polypots in all sizes.

2. Close nesting in trays prevents inter-cell areasfrom filling with soil in which weeds can grow.

Disadvantages1. There are no internal ribs to prevent root spiral-

ing.2. Air-pruning is impossible unless trays are ele-

vated.3. Boots frequently entwine between pots via vent

holes.4. More medium is required for filling than for

other, similar-length containers having moderate orstrong taper.

III. Suppliers of Commercial Potting Mixes

Agritec Co., Inc.939D MilweeHouston, TX 77018(synthetic soils, plant starter blocks)

J-M Trading Corporation307 S. Lawndale AvenueChicago, IL 60623(HECO soil replacer)

Jiffy Products of AmericaP. 0. Box 338West Chicago, IL 60185(distributor of Jiffy-Mix, Jiff-Mix Plus, Grower’sChoice, and Magamp products)

McConkey Co., Inc.P. 0. Box 309Sumner, WA 98390(perlite, soil conditioners, and fertilizers)

Sierra Chemical Co.7650 Sycamore StreetNewark, CA 94560(Osmocote slow-release fertilizers)

A. H. Hummert Seed Company746 Chouteau AvenueSt. Louis, MO 63103(prepared pot mixes, vermiculite)

E. C. Geiger CompanyBox 285, Route 63Harleysville, PA 19438-0332(general nursery supplies and equipment)

Griffen Greenhouse Supplies, Inc.6 Interstate AvenueAlbany, NY 12205(general nursery supplies, including irrigation equip-ment)

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IV, Split-Level Nursery Operations for Producing Container Stock

In split-level operations, gravity feed is used when-ever possible to compliment semi-automatic mechani-cal equipment. Such a setup reduces energy expenseswhile reducing need for additional operators and ma-chinery. Efficiency of operation may be somewhatlower for split-level operations than for fully mecha-nized operations. Yet some countries prefer less mech-anized operations that require lower establishmentcosts, less time to repair when machinery breaksdown, and fewer problems in finding workers who canoperate the equipment. A key feature of any semi-mechanized operation is a tractor-mounted loaderhaving a capacity of at least 0.5 m3. End loaders areefficient for loading heavy soil and sand into the soilsieve and for moving sieved potting medium into themixer (fig. Al&l). Mixers should have a capacity of 2m3.

After a proper soil mix is prepared and dumpedfrom the mechanical mixer, the end loader scoops upthe mixture and fills each available hopper. Hoppersshould be filled early in the morning before the labor-ers (bag fillers) arrive or late in the afternoon, after

workers have left. Hoppers are easily designed to hold1 to 1.5 m3 of pot mix. These amounts give bag fillersa full day’s supply of mix in their respective hoppers.

Most bag-filling operations in tropical nurseries arerun on an incentive basis. A particularly effectivemethod is to employ women on a part-time basis.Since most women have domestic chores at home,they are particularly eager to leave early in the after-noon. If a set price is arranged for emptying a singlehopper load, worker morale will be high. In a trial inPuerto Rico, a nursery manager told bag tillers theywere free to leave after they had filled 800 bags. Notsurprisingly, what was previously an &hour task wasaccomplished in about 6-hours. Other nurseries haveeffectively employed a fixed price per filled bag. Thisallows individuals who wish to earn extra money to doso. What should be avoided is a fixed daily wage with-out any control over production output. Such a policyusually causes a serious work backlog that slowsother operations.

From time to time, a quick check is necessary todetermine whether the mechanical mixer is mixing

AJOR CONTAINERIX COMPONENTS

Figure A15-l.-Overhead view of split-level structure used in producing container nursery stock with semi-automated procedures. Natural topography was used for best placement of structure and approachramps.

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soil components in desired ratios. A simple samplingmethod is to pull out about 3 to 4 liters of the mixtureand sieve it by hand. This procedure is repeated sev-eral times and an average computed. If computed ra-tios deviate excessively, mix proportions must be ad-justed accordingly.

As bags are filled, they are placed in trays (with acapacity of 35 to 45 bags) and loaded onto pallets.Filled pallets are transferred to a flat bed wagon,taken to nursery beds, and off-loaded; workers line-out bags in rows. This operation can also be donemechanically by placing filled trays on roller convey-ors and pushing them to a worker who removes thetrays and loads them onto a wagon.

Often, natural terrain of a nursery allows construc-tion of a split-level structure. If not, a simple rampand elevated floor can be constructed by backfillingbehind a fence (fig. A152).

I

15 cm OF CONCRETE OVERDIRT FILL u RAMP

LITERATURE CITED

1. Barnett, James P.; McGilvray, John M. Containerplanting systems for the South. Res. Pap. SO-167.New Orleans, LA: U.S. Department ofAgriculture, Forest Service, Southern ForestExperiment Station; 1981. 19 p.

2. Tinus, Richard W.; McDonald, Stephen E. How togrow tree seedlings in containers in greenhouses.Gen. Tech. Rep. RM-60. Ft. Collins, CO: U.S.Department of Agriculture, Forest Service,Rocky Mountain Forest and Range ExperimentStation; 1979. 256 p.

3. Venator, C. R.; Rodriguez, A. Using Styroblockconta iners la g r o w Pinus curibaeu v a r .hondurensis Barr. & Golf. nursery seedlings.Turrialba. 27(4): 393-396; 1977.

4. Walters, Gerald A. Seedling containers forreforestation in Hawaii. In: Tinus, Richard W.;Stein, William I.; Balmer, William E., eds.Proceedings of the North American containerizedforest tree seedling symposium; 1974 August26-29; Denver, CO. Great Plains AgriculturalCouncil Publ. 68. Washington, DC; 1974:336-338.

Figure AIS-2.-Split-level structures can also be built on level ter-rain by filling in a fenced area behind pilings andscreen, and hauling in fill dirt for approach ramps.

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Appendix 16

Practical Guides on Watering and Soluble-Fertilizer Application

I. Watering System Alternatives for Forest NurseriesII. General Management Scheme for Watering Nursery Seedlings

III. Injector Alternatives for Soluble-Nutrient Watering Systems

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I. Watering System Alternatives for Forest Nurseries

Many traditional nurseries and almost all mecha-nized nurseries have overhead watering systems. Sys-tems with automatic controls save labor and providedependable water delivery. A multiple water stationarrangement, controlled from a single panel, allowsone to direct water to some nursery areas but simulta-neously to exclude it from others. This feature saveswater and maintains flexibility within the nurserycomplex.

Commercial nursery supply catalogs should be con-sulted before any system is installed. Three generaltypes of water delivery systems are: mist, continuousspray, and impulse (3). The mist system delivers avery fine, uniform water coverage as long as strongwinds do not blow the mist off designated beds. Mistirrigation is ideal for germination flats because thefine water drops do not pack germination medium orwash seeds from the flats. Mist systems require about280 to 350 g/cm2 of water pressure for each nozzle. Asmany as 100 mist nozzles can be operated on onewater line if booster pumps and tanks are used toincrease water line pressure. Booster pumps are moreeconomical to operate than elevated water-storagetanks that have a high pressure head of water.

Continuous spray nozzles have larger openings anddeliver more water in a given time period than mistnozzles; they also cover larger areas. Thus, they tendto clog less than mist nozzles, are easier to clean onceclogged, and water droplets are less likely to be blownabout by wind.

Impulse systems work by water pressure from ramor other pumps. Water is ejected in a stepwise circularpattern, nozzles rotating several degrees as each jet ofwater is released. The nozzles are designed to spray aradius of up to 15 m or a diameter of 30 m. Since wateris shot into the air, it falls back as large dropletssimilar to rainfall. This irrigation system is the sim-plest type. It is readily purchased as a portable systemthat is hooked into a main water line (>7.6 cm indiameter) within a few minutes.

Impulse systems are most efficient for bare-rootbeds in which water easily diffuses throughout thesoil, a more difficult process when seedlings are incontainers. Containizered nurseries in Hawaii and inthe Blakawatra nursery in Surinam have successfullyused impulse sprinkler systems. However, nurseriesin both countries used rigid-walled containers. Non-rigid bag tops, e.g., plastic bags, tend to collapse, im-peding water from entering soil in the bags.

Basic knowledge of water pressure and flow are de-sirable when nursery managers do not have access toa hydrologist or pump technician. The data belowwere calculated from formulas in a basic text on hy-draulics (1). Average atmospheric pressure is as-sumed to be 1,033 g/cm2, and the specific weight ofwater is 304.8 kg/m2 (at 21°C). If a barometer wereconstructed using water, the water column at normalatmospheric pressure would rise to 10.3 m; with aslight correction, because of vapor pressure, height ofthe column would actually be 10.1 m.

By association, a water column that is 0.7 m highexerts a pressure (i.e., has a hydraulic “head”) of 70.3g/cm2. Estimates of water pressure can then be madefor storage tanks of known heights by using this rela-tionship:

Pl p2-=-

HI H2

where P1 = standard atmospheric pressure (1,033g/cm2>,

P2 = potential pressure (g/cm21 exerted bywater in any storage tank,

H1 = height of water column (ml at standardatmospheric pressure,

and H2 = height of water (ml in storage tank.

For example, if a water tank is 30.5 m above anursery area, the potential pressure for any irrigationsystem is:

1,033 g/cm2 = P2 g/cm2 and, by rearranging10.1 m 30.5 m and simplifying,

(102.3) x (H2) = I$, or

(102.31 x (30.5) = 3,120 g/cm2 .

Similarly, other reference examples are:

Head or height Pressureof water supply (m) (glcm2)

0.3 303.0 3104.6 470

15.2 1,55022.9 2,34030.5 3,120

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11, General Management Scheme for Watering Nursery Seedlings

The following guides should help in determiningcorrect application of water for nursery seedlings. Theguides are generally applicable to containerized andbare-root stock in traditional or mechanized systems.

TRANSPLANT STAGE TO 3 WEEKS LATER

1. When necessary, lift several seedlings to checkroot growth. Check the soil daily for moisture needsduring the first 2 weeks. Do not check the surfacealone but rather the zone between 2 and 10 cm belowthe surface; this is the root zone that needs water.

2. If shade is used for 2 weeks following transplant-ing, adjust watering to actual soil conditions andneeds.

3. The first 3 weeks is critical for watering becauseexcess soil moisture causes damping-off. Never addfertilizer in a water soluble form during this stage.

3 WEEKS TO 2 MONTHS

1. Cut back on watering frequency. If very sandysoil is used in containers, do not under-water.

2. Watch for hypocotyl and stem growth change towoody tissue. When this physiological change occurs,water soluble fertilizers can be applied.

3. Maintain soil surface somewhat drier to avoidmoss build up.

4. If not added before sowing, add mycorrhizalfungi to watering can and sprinkle seedlings duringthe fourth, fifth, and sixth weeks.

5. Inspect bottoms of bags; do not let water accumu-late there.

6. Inspect sides of bags. If roots are concentrated inouter space between soil and bag, poor aeration isindicated. Reduce shade, if any, and cut back onwatering.

2 TO 4 MONTHS

1 . Use water soluble fertilizers at highest rates pos-sible that do not cause excessive branching and exces-sive greening.

2. When adding fertilizers to irrigation water, do soat the end of watering periods to prevent fertilizer

from washing out of containers, but rinse foliage withunfertilized water before ending the irrigation cycle.

3. Water as often as necessary to maintain a vigor-ous, succulent flush.

4. Avoid water stresses that can make seedlingssemi-dormant in this stage.

5. Avoid heavy use of chlorinated or high-salt-content water.

6. When possible, use a soil moisture tester (ten-siometer) to determine water tension in the soil.Probes are placed in the root zone area, with at leastthree readings per bed, each taken at a different posi-tion.

7. If a soil solu-bridge tester is used to take conduc-tivity readings, more accurate readings are obtainedbefore fertilization rather than afterwards. Solublesalts released by fertilizers tend to increase conductiv-ity between the electrodes, causing a bias. Also, use aprobe having the smallest possible diameter to avoidphysical damage to the roots. Do not excessively wig-gle the probe; this allows poor contact with the sur-rounding soil.

4 TO 7 MONTHS

1. Pine seedlings and most other subtropical spe-cies are ready for outplanting 5 to 7 months aftergermination. Thus, if hardening-off of seedlings is re-quired, now is the time to do so.

2. Hardening-off is not entirely possible with semi-dormant pines. As a minimum, one tries to reducesucculent tissue growth by gradually decreasingwatering frequency.

3. Bagged P. curibaeu seedlings in clay loam soilnormally survive 24 days or longer without water.However, serious damage occurs to seedlings grown insmall volume containers filled with peat-based mix-tures if more than 8 days go by without water. Deathoften occurs within 16 days if there is no watering.The best guide for nursery managers is experimenta-tion with size of seedlings desired, preferred containertype, and potting medium used. Because climatic con-ditions are different for each country, only experienceand experimentation will indicate which waterregime is best for a given species/container/pot mixcombination.

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III. Injector Alternatives for Soluble-Nutrient Watering Systems

Several types of liquid fertilizer injectors are avail-able. The basic components of a precisely controlledinjection system are:l storage tank with an internal agitator to keep the

solution thoroughly mixed;l filter on the outer valve of the storage tank;l pump that controls rate of injection into water lines,

and. pressure relief valve for the storage tank inlet and

outlet valves.Because of the corrosive nature of fertilizers, al-

ways use tanks, water lines, and pumps made of corro-sion-resistant materials. Some leeway exists aboutthe type of design needed to ensure adequate fertiliza-tion through nutrient injectors. Snedigar (2) pre-sented the design for a simplified nutrient injector. Itoperates by air pressure within storage tanks, not bywater-operated or motor-driven pumps. A skilled ma-chinist can construct a similar injection system if hehas blue prints or a diagram of the system used. Gen-erally, for commercially bought units, the more ex-pensive units give more precise injection rates.

Nutrient injectors are also activated by flowmeters.

In one design, a watermeter installed in the waterpipe counts the flow of water in liters. A solenoid ontop of the water pump receives an electronic signalfrom the water-meter, which indicates water flow inthe irrigation line. The solenoid valve then opens andfeeds an exact proportion of fertilizer into the waterline to make up the required dilution.

LITERATURE CITED

1. King, H. W.; Wisler, C. 0.; Woodburn, J. G. 5th ed.Hydraulics. New York: John Wiley and Sons;1948. 351 p.

2. Snedigar, Carl F. Nutrient injector. In: Tinus,Richard W.; Stein, William I.; Balmer, WilliamE., eds. Proceedings of the North American con-tainerized forest tree seedling symposium; 1974August 26-29; Denver, CO. Great Plains Agri-cultural Council. Publ. 68. Washington, DC:1974.458 p.

3. Woodward, Guy 0. 2d. ed. Sprinkler irrigation.Washington, DC: Sprinkler Irrigation Associa-tion; 1959. 377 p.

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PESTICIDE PRECAUTIONARY STATEMENT

Pesticides used improperly can be injurious to man, animals, and plants. Follow thedirections and heed all precautions on the labels.

Store pesticides in original containers under lock and key-out of the reach of childrenand animals-and away from food and feed.

Apply pesticides so that they do not endanger humans, livestock, crops, beneficial insects,fish, and wildlife. Do not apply pesticides when there is danger of drift, when honey bees orother pollinating insects are visiting plants, or in ways that may contaminate water or leaveillegal residues.

Avoid prolonged inhalation of pesticide sprays or dusts; wear protective clothing andequipment if specified on the container.

If your hands become contaminated with a pesticide, do not eat or drink until you havewashed. In case a pesticide is swallowed or gets in the eyes, follow the first-aid treatmentgiven on the label and get prompt medical attention. If a pesticide is spilled on your skin orclothing, remove clothing immediately and wash skin thoroughly.

Do not clean spray equipment or dump excess spray material near ponds, streams, orwells. Because it is difficult to remove all traces of herbicides from equipment, do not use thesame equipment for insecticides or fungicides that you use for herbicides.

Dispose of empty pesticide containers promptly. Have them buried at a sanitary land-filldump, or crush and bury them in a level, isolated place.

Use of trade, firm, or corporation names is for the reader’sinformation and convenience. Such use does not constitute officialendorsement or approval by the U.S. Department of Agricultureof any product or service to the exclusion of others that may besuitable.

Liegel, Leon H.; Venator, Charles R. A technical guide forforest nursery management in the Caribbean and LatinAmerica. Gen. Tech. Rep. SO-67. New Orleans, LA: U.S.Department of Agriculture, Forest Service, Southern ForestExperiment Station; 1987. 156 p.

Presents a comprehensive summary of forest nursery prac-tices for the Caribbean, tropical Latin America, and, to alesser degree, other tropical areas in the world. Actual andrecommended practices are discussed, and the advantagesand disadvantages of each are given with specific exampleswherever possible. Included are chapters covering overallnursery planning, general seed management, and small- andlarge-scale nursery operations.

Additional keywords: Seedbed preparation and sowing,container and bare-root systems, pest and disease control,nursery nutrition.

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