Fores~~;ology

Management

Forest Ecology and Management 80 (1996) 267-278

Effect of site preparation techniques on Prosopis juliflora in an alkali soil

Gurbachan Singh Central Soil Salinity Research Institute, Karnal132 001, India

Accepted 8 February 1995

Abstract

Effects of three methods of site preparation, i.e. trench (30 cm deep and 30 cm wide dug across the plots), pit (30 cm x 30 cm x 30 cm) and augerhole (15 cm diameter and 90 cm deep) on raising Prosopis juliflora plantations on a highly alkali soil (pH, 10.3) were studied in a field experiment at Gudha Experimental Farm of the Central Soil Salinity Research Institute, Kamal. A uniform dose of gypsum of 3 kg per plant was mixed with the excavated soil before trenches/pits/ augerholes were refilled and Prosopis planted. The study indicated that mean plant height and girth growth, recorded at 2 year intervals from planting up to 8 years, were greatest with the augerhole method. Similarly, the air dried shoot and root biomass accumulated by Prosopis in 6 years was maximum in augerhole planting. In trench and pit planting, most of the roots were confined to surface layers (O-60 cm>, whereas in augerhole the roots were able to pierce the hard CaCO, layer (caliche bed) and were nearly 2.5 m deep 2 years after planting. Differential site preparation techniques showed little effect on N, P, K, Ca, Mg, S and Na concentrations in plant parts (leaf, branch and stem) of Prosopis both at 2 and 6 years after planting. Total removal of N, P, K, Ca, Mg and S through Prosopis parts at 2 and 6 years after planting was maximum in auger planting and minimum in trench planting. The augerhole was also superior to other techniques in pod production, litter yield and nutrient additions to the site. However, litter quality remained unaffected owing to planting techniques. In general, there was marked decrease in pH and electrical conductivity and appreciable improvement in organic carbon and available N status of the experimental soil owing to Prosopis growth, but effect of different site preparation methods was not significant. This study showed that site preparation for planting Prosopis in high pH soils in the vertically downward direction is more important than reclamation of surface soil in the horizontal direction.

Keywords: Prosopis; Site preparation; Alkali soil; Soil rehabilitation

1. Introduction

Soil salinity and alkalinity have caused the degra- dation of about 8 million ha of land in India (Singh, 1992). Worldwide, such soils are spread over an area of about 952 million ha (Szabolcs, 1977). Large tracts of salt-affected soils in India are confined to community lands near villages, as public properties near cities, along the railway tracks and roads, and

government lands reserved for specific purposes. These areas of land do not contribute to national output and present a picture of desolation. There is a need to revegetate these wasted lands and prevent their further degradation. Afforestation is an option of great promise for use of such lands, in view of the growing demand for fuelwood and fodder and also on environmental considerations. For reclamation and management purposes, salt lands in India are broadly

0378.1127/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved .SSDr0378-1127(95)03543-5

268 G. Singh / Forest Ecology and Management HO (19961267-278

Table 1

Soil properties of the experimental site

Soil Mechanical analysis (%I

depth Sand Silt Clay cm

o- 15 51.4 28.3 20.3

15- 30 43.5 31.5 25.3 30- 60 42.8 32.0 25.2 60- 90 37.0 34.2 28.8

90-120 32.4 40.5 27.1

” Measured in I : 2 soil: water suspension.

’ Exchangeable sodium percentage.

PH

10.3

10.3

10.1 10.2

10.2

ESP b

94

93 90

91 92

.- OC Available nutrients

-. (%i N P P

--_--_---~.- .-.--. .-- 0. I7 x2 3s 5.3 7

0.12 77 . 28 488 0.10 h0 20 140

0.10 42 18 156 0.10 34 14 300

-._l.----- --

placed under two groups: alkali (sodic) and saline. About one-third of the reported salt-affected soils in India are alkali and are characterised by high pH values of over 8.2, high levels of carbonates and bicarbonates of sodium, exchangeable sodium per- centage (ESP) above 15, variable electrical conduc- tivity (EC), low fertility and very poor physical properties, which support very little vegetation.

Hard CaCO, layers in the profile also act as physical barriers for vertical penetration of roots. These layers offer high penetration resistance. Thus, mechanical impedance is a major cause of poor root proliferation in dense alkali soils and this has been a

major cause of either the complete failure or reduced growth of even hardy tree species like Prosopis when planted on alkali waste lands. Overcoming this problem by modifying soil environment using appro- priate site preparation techniques is a basic require- ment for successful establishment of trees in alkali soil. Khan and Yadav (1962) and Pande (1967) suggested replacement of alkali soil with good soil from a normal site and the use of 90 cm deep pits, filled with good quality soil, was advocated. This method involved removal of soil from a productive site, thereby disturbing its natural topograpky and the need for disposal of excavated soil. Later, it was

Fig. 1. Original landscape of alkali land. Such soils constitute nearly 2.5 million ha in northern India.

G. Singh / Foresf Ecology and Management 80 (I 996) 267-278 269

found that the original alkali soil could be dispensed with if mixed with 10 kg gypsum or gypsum equiva- lent to 50% gypsum requirement of the excavated soil plus 24 kg farm manure before returning the mixture to the pit (Yadav et al., 1972; Sandhu and Abrol, 198 1). This method also suffered from many drawbacks such as: (i) high requirements of amend- ments; (ii) high labour requirement; (iii) greater amount of earth work, (iv> non-perforation of the hard layer. The aim of this study was to evaluate the effects of varying site preparation techniques on Prosopis juliflora.

2. Materials and methods

2.1. Experimental site

This long-term study (1984-1992) was conducted at the Gudha Experimental Farm of the Central Soil Salinity Research Institute, Kamal. The farm is lo- cated at 29”29’ and 76”56’ and is about 237 m above mean sea level. The water table fluctuates between 4 and 6 m and the groundwater is of good quality. The soils are Aquic Natrustalfs (Bhargava et al., 1980), representative of large areas of sodic soils occurring in the Indo-Gangetic plains (Table 1). The natural vegetation is very scanty (Fig. 1). There are isolated trees of Acacia nilotica, Acacia tortilis, Prosopis julij‘lora, Capparis aphylla, Salvadora spp. and Butea monosperma, with a sparse understory of

Sporobolus marginatus, Sporobolus diander, Desmostachya bipinnata, Leptochloa fisca, Suaeda

maritima and Chloris gayana.

2.2. Climate

The study area represents a typical sub-tropical, semi-arid, monsoonic type of climate characterised by a dry and hot spring/early summer, a hot rainy season, a warm autumn and a cool winter. The average annual rainfall is about 700 mm, with 80% received between June and September. The tempera- ture starts rising from February onwards until the summer maximum, often exceeding 40°C is reached in May or June. The mean monthly minimum tem- perature is recorded in January. There is ample sunshine throughout the year. Class A pan evapora- tion exceeds rainfall except in July and August. Mean meteorological parameters as recorded near the experimental site during the study period are reported in Table 2.

2.3. Experimental layout

The effects of three methods of site preparation for planting Prosopis juliflora were studied in a field trial with randomised block design, replicated four times. Plot size was 10 m X 24 m and each plot accommodated 16 trees. The three site preparation methods were trench (30 cm deep and 30 cm wide, dug across the plots), pit (30 cm X: 30 cm X 30 cm)

Table 2 Mean monthly climatalogical parameters as recorded near the experimental site during the study period (1984-1992)

Month Temp. (“C) Rainfall Pan Dailv

Max. Min. evap. (mm month- ’ )

sunshine

(h)

Jan. 19.1 6.4 10.2 45.3 7.3

Feb. 22.0 8.1 44.3 65.1 1.6

March 27.2 12.1 21.7 117.2 8.3

April 35.3 15.3 9.1 213.8 9.7

May 38.7 21.6 27.3 296.7 9.4

June 34.7 25.6 68.4 249.4 7.8

July 33.8 26.0 172.7 146.1 6.5

Aug. 32.8 25.4 210.8 117.7 6.1

Sept. 32.8 22.4 100.0 118.1 7.2

Oct. 31.0 16.3 22.2 96.5 8.0

Nov. 27.1 11.1 13.0 59.8 7.7

Dec. 21.8 7.7 30.8 45.0 6.2

270 G. Singh/ Forest Ecology and Management 80 (1996) 267-278

and augerhole (15 cm in diameter and 90 cm deep, dug with soil sampling augers). These trenches/ pits/augerholes were refilled with a mixture of the original excavated soil blended with 3 kg gypsum per tree before planting. Prosopis saplings, 4-6 months old, raised in a good normal soil in polythene bags were transplanted in July 1994 keeping inter- plant and inter-row distances of 3 m and 5 m, respectively. The first irrigation was given immedi- ately after planting, and subsequent irrigations were applied as and when required, at intervals of 15-20 days in summer and 25-30 days after the July-Sep- tember monsoon season up to 2 years after planting. Good quality water from a shallow tubewell was used for irrigation.

2.4. Observations recorded

Data on height and girth growth of Prosopis were recorded periodically but the results are discussed on the basis of observations recorded at 2 year intervals up to 8 years after planting. The diameter at stump height (DSH) and at breast height (DBH) were mea- sured at 5 cm and 137 cm above ground level, respectively. The average initial height and DSH of Prosopis at planting were 55 cm and 5.5 mm respec- tively. After 2 and 6 years, representative plants were harvested from each treatment to study the biomass accumulation in different treatments. Prosopis leaves, branches and main stem were sepa- rated and their fresh and air dry weights recorded. The roots were exposed by excavating the earth following the methodology suggested by Bohm (1979).

For collection of litter, wooden traps (7.5 cm long, 5 cm wide, 10 cm high) were used. These traps

were placed at representative sites in the experimen- tal field. The litter collected in these traps was weighed four times during the year (March, June, September and December). Prosopis pod yields were also recorded. An area of 5 m X 3 m was marked at four places in each treatment for this purpose. Pods fallen in this area were collected periodically and weighed to work out tentative yearly yields.

2.5. Collection, preparation und analysis of soil samples

Soil samples were taken at four places for each plot before Prosopis planting, giving 16 samples from each treatment. Sampling was repeated in September 1990 (6 years after planting) to assess improvement in soil properties. After collection, samples were air- and then oven-dried, ground in a wooden pestle and mortar, passed through a 2-mm sieve and stored for analysis. The soil pH, EC, organic carbon and available N, P, and K were determined by standard procedures (Jackson, 1%7).

2.6. Collection, preparation and analysis of plant samples

Stem, branch and leaf samples were analysed separately for chemical composition. Samples were washed with ordinary water, dilute acid (0.1% HCl), and single and double-distilled water, air- and oven- dried at 70°C for 48 h, ground in a Wiley mill, passed through a 16-mesh sieve, and stored in polyethylene bags. Samples of 1 g were digested in a di-acid mixture (HNO,:HClO, 3: 1). The filtrate was preserved in 100 ml plastic bottles. The samples were analysed for Na and K by flame photometry, and for Ca, Mg, Fe, Mn, Zn and Cu by Pye Unicam

Table 3 Effect of site preparation methods on height and girth growth of Prosopis

Site preparation Height (m) DSH (cm)

method 2” 4 6 8 2 4

Trench 3.2 4.3 6.9 8.2 3.9 5.6 Pit 3.2 4.4 7.0 8.4 4.8 6.9 Augerhole 3.6 4.7 7.7 9.3 4.7 7.7 LSD (0.05) NS NS NS NS 0.7 1.4

’ Years after planting.

-...---- _.__ -- DBH km)

--__ 6 8 2 4 6 8

- 7.9 10.0 1.4 3.3 6.4 7.8 8.4 10.9 1.7 3.6 6.7 8.4 9.6 12.0 1.7 3.8 7.9 9.7 1.3 1.6 NS NS 1.2 1.4

-_l.-

G. Singh / Forest Ecology and Management 80 (1996) 267-278 271

atomic absorption spectrophotometry. Total N was determined by a Kjeltec-II automatic nitrogen anal- yser. Phosphorus was determined by the vanado- molybdophosphoric-yellow colour method (Jackson, 1967) and S by a turbidity method (Massoumi and Cornfield, 19631, using spectrophotometer model Spectronic 2 1.

3. Results and discussion

3.1. Height and girth growth

Mean Prosopis height, recorded at 2 year inter- vals from planting up to 8 years, was greatest in augerhole planting (Table 3). Similarly, plant diame- ter, both at stump height (DSH) and breast height (DBH), was significantly greater in augerhole com- pared with trench planting. Overall effect of site preparation techniques on Prosopis growth was in the order: augerhole > pit > trench. Differences in response to site preparation are largely ascribable to

the volume of soil in which gypsum was mixed, causing differential improvement in soil alkalinity.

3.2. Biomass production

Effects of site preparation techniques on biomass production of 2 and 6 year old Prosopis are reported in Fig. 2. At 2 years, total biomass accumulated in stem, branches and leaves by Prosopis was signifi- cantly more when trees were planted using the pit and augerhole techniques than in case of trench planting. However, 6 years after planting, the total biomass production was much higher in auger plant- ing than in trench and pit planting; the latter two being statistically similar. More than 80% biomass was accumulated in stem and branches and leaves formed less than 20% of the total biomass. The trees were pruned of side branches at 16 and 40 months after planting to give the trees a proper shape. The pruned biomass attained in 6 years was also maxi- mum (6.4 t ha- ’ ) in augerhole followed by pit (6.0 t ha-‘) and trench (4.7 t ha-‘) planting.

Fig. 2. Effect of site preparation techniques on total biomass accumulation by Frosopis 2 and 6 years after planting.

272 G. Singh / Forest Ecology and Management 80 (1996) 267-278

Table 4

Root biomass (kg ha- ’ ) of Prosopis in different layers of the profile under different planting techniques 2 years after planting

Soil depth

(cm)

Planting technique LSD (0.05)

Trench Pit Augerhole

o- 30 382 338 162 32 30- 60 50 106 128 26 60- 90 - 28 114

90- 120 - .- 16 120-150 - 96

Total 432 472 576 46

3.3. Root distribution

Root systems of Prosopis were exposed in the field after 2 years following wet excavation method- ology (Bohm, 1979) to study treatment effects on root development pattern and root biomass. The oven dried root biomass accumulated by Prosopis in 2 years (Table 4) was maximum in augerhole planting followed by pit and trench planting. It was found that Prosopis roots were mainly confined to the soil mass amendment mixture in the trench/ pit/ augerhole (Fig. 3). Roots of augerhole-planted Prosopis which grew beyond the hard pan were nearly 2.5 m deep within 2 years. Root growth in the horizontal direc- tion was less, however in trench planting, the major- ity of roots remained in the amended soil and fol- lowed a horizontal path, instead of growing verti- cally. Only very few roots penetrated beyond 30 cm depth. Such a shallow root system can expose the plant to vagaries of strong winds and moisture stress. In the pit planting method, the whole root system was confined to the pit soil; only one or two roots reached the hard pan but did not penetrate it. Gyp- sum was also mixed with the whole surface soil as is done for reclamation of alkali soils for growing crops. In this situation too, the Prosopis roots were spread uniformly throughout the amended surface soil. Root extension downwards was lacking. These observations revealed that for the planting of trees in alkali soils, site preparation in a vertical direction is more important than in a horizontal direction. Auger- hole method of site preparation allows tree roots to circumvent the hard subsurface layers and as roots

reach the lower less deteriorated and coarser soil depths, they proliferate and boost top growth.

3.4. Chemical composition and total accumulations

The effects of site preparation methods on mean nutrient concentrations in different parts of Prosopis at 2 and 6 years after planting are given in Table 5. At both stages, the nutrient concentrations in various parts decreased in the order: leaves, branches, stem. The nutrient concentrations in parts of Prosopis represent medium to high levels reported for many temperate trees (Leaf, 1973) and are comparable to multispecies averages obtained in analysis of tropical forest ecosystems (Galley et al., 1975; Lundgren. 1978; Steward et al., 1981; Singh, 1982). This nutri- ent concentration trend is commonly encountered in nutrient analysis of tree components CLundgren, 1978; Steward et al., 1981; Singh, 1982).

In general, concentrations of almost all the nutri- ents in leaves, branches and stem of Prosopis were

Fig. 3. Root development of Prosopis (clockwise): in an auger- bore 15 cm in diameter and 90 cm depth; in a pit of 30 cm X 30 cm x 30 cm; when gypsum was mixed with the surface soil; in a

trench 30 cm wide and 30 cm deep dug across the plots.

Tabl

e 5

Nutri

ent

conc

entra

tions

(8

) in

di

ffere

nt

parts

of

Pr

os@

2

and

6 ye

ars

afte

r pl

antin

g

Site

Pl

ant

2 ye

ars

prep

ar-

atio

n Pa

rt \

N P

K Ca

Mg

S

Na

N P

K Ca

Mg

S

Na

2 ;;:

met

hod

h h

Tren

ch

Leaf

8

3.3

0.24

1.

8 1.

6 0.

69

0.69

0.

62

2.6

0.19

1.

7 1.

6 0.

43

0.6

0.2

3 Br

anch

1.

1 0.

11

0.9

0.60

0.

09

0.13

0.

17

0.76

0.

08

0.96

0.

66

0.08

0.

06

0.06

P

Stem

0.

8 0.

09

0.7

0.39

0.

11

0.13

0.

10

0.38

0.

05

0.21

0.

38

0.02

0.

03

0.02

it

Mea

n 1.

7 0.

15

1.1

0.9

0.30

0.

32

0.30

1.

3 0.

11

0.98

0.

88

0.18

0.

23

0.09

?

Pit

Leaf

3.

3 0.

24

1.8

1.7

0.59

0.

79

0.40

2.

8 0.

20

1.9

1.7

0.52

0.

5 0.

2 B

Bran

ch

1.0

0.08

0.

9 0.

63

0.10

0.

15

0.10

0.

82

0.10

1.

04

0.73

0.

07

0.06

0.

04

3 St

em

1.0

0.07

0.

8 0.

49

0.09

0.

14

0.08

0.

44

0.04

0.

32

0.36

0.

02

0.03

0.

02

ii

Mea

n 1.

8 0.

13

1.2

0.9

0.26

0.

36

0.19

1.

4 0.

11

1.1

0.93

0.

20

0.20

0.

09

53

;2

Auge

rhol

e Le

af

3.9

0.25

2.

2 1.

47

0.79

0.

77

0.50

2.

4 0.

19

2.0

1.5

0.40

0.

5 0.

2 s

Bran

ch

1.2

0.13

1.

2 0.

60

0.13

0.

17

0.14

0.

70

0.08

0.

88

0.61

0.

06

0.07

0.

02

3 St

em

1.1

0.07

0.

8 0.

40

0.14

0.

14

0.11

0.

36

0.04

0.

25

0.32

0.

03

0.03

0.

02

z M

ean

2.1

0.15

1.

4 0.

8 0.

35

0.36

0.

25

1.2

0.10

1.

0 0.

81

0.16

0.

20

0.08

;” Y 0

274 G. Singh/Forest Ecology and Management 80 (1996) 267-278

. 600

Trench ’ Pit ’ Augerhole ’ LSD (0.05) ’

/ - After 2 years m After 6 years /

Fig. 4. Total accumulation of N, P, K, Ca. Mg and S by Prosopis 2 and 6 years after planting under different planting techniques.

higher at 2 than at 6 years after planting. This may be owing to dilution effect as biomass production at 6 years was nearly 15 times that at 2 years. The differential site preparation techniques had little ef- fect on N, P, K, Ca, Mg, S and Na concentrations in leaf, branch and stem tissues of Prosopis.

Nutrient accumulations were calculated by multi- plying nutrient concentrations by the respective weights of Prosopis parts. At 2 years, total accumu- lation of N, P, K, Ca, Mg and S by Prosopis was significantly higher in augerhole than in trench plant- ing (Fig. 4). However, such differences between the augerhole and pit methods were not significant. Even 6 years after planting the differences in nutrient uptake amongst different site preparation methods were very small. This study further showed that Prosopis has the advantage of fixing a greater quan- tity of nutrients in the leaves, a tree part which is likely to be left at the site during harvesting. This helps to mitigate site depletion problems arising

from high nutrient removals through Prosopis har- vesting.

3.5. Litter production, its quality and nutrient addi- tions

The effects of site preparation methods on litter yields of Prosopis were recorded annually from 1986- 1987 to 1990- 199 1 and the total yields during the study period are reported in Fig. 5. The litter yields from trees planted using the augerhole tech- nique were higher than those planted using pit and trench methods, apparently due to better tree growth in the augerhole treatment. Irrespective of site prepa- ration methods, litter production by Prosopis also increased regularly from year to year.

The effect of site preparation methods on litter quality was not significant (Table 6). On average, Prosopis litter contained 2.45% N, 0.22% P, 1.43% K, 1.12% Ca, 0.48% Mg, 0.42% S and 0.18% Na. Similarly, the effect of site preparation methods on

G. Singh/ Forest Ecology and Management 80 (1996) 267-278 215

Trench Pit Augerhole

Fig. 5. Effect of site preparation techniques on total litter and pod yields during the study period.

nutrient additions through tree litter was also negligi- ble. Total amount of nutrients added to the soil through litter amounted to 913.3 kg, 956.0 kg and 1050.1 kg ha-’ in trench, pit and augerhole treat- ments, respectively. Irrespective of the treatments, 373.2 kg, 34.4 kg, 216.0 kg, 171.5 kg, 72.9 kg, 62.8 kg and 27.3 kg ha-’ N, P, K, Ca, Mg, S and Na, respectively was added through the litter during the study period. Such high nutrient additions may raise

fertility status of alkali soils which otherwise would have poor fertility status.

3.6. Pod production

Prosopis started podding in the third year and continued to pod annually throughout the study pe- riod. Total pod yields during the study period were maximum in augerhole planting and minimum in

Table 6 Mean concentration of nutrients in Prosopis litter and nutrient additions to the site through litter fall

Nutrient Mean concentration (56) Nutrient additions (kg ha-’ )

Trench Pit Auger LSD Trench Pit Auger LSD (0.05) (0.05)

Nitrogen 2.38 2.52 2.46 NS 350.6 375.3 393.7 NS Phosphorus 0.24 0.23 0.21 NS 35.4 34.2 33.6 NS

Potassium 1.40 1.46 1.43 NS 206.2 212.9 228.9 NS Calcium 1.12 1.10 1.16 NS 165.0 163.0 185.7 NS Magnesium 0.48 0.50 0.46 NS 70.7 14.5 13.6 NS

Sulphur 0.40 0.20 0.16 NS 26.5 29.8 25.6 NS Mean/total 0.89 0.92 0.90 913.3 956.0 1005.1 -

216 G. Singh / Forest Ecology and Management 80 (1996) 267-278

Table 7

Changes in soil properties (O-30 cm) recorded 6 years after planting under different treatments

Soil property Initial After 6 years

Trench Pit Auger

planting planting planting

PH 10.3 9.6 9.6 9.5

EC (dS m-l) 1.9 0.60 0.56 0.50 Organic carbon 0.15 0.30 0.34 0.36

(%) Available N 76 120 112 118

(kg ha- ’ ) Available P 33 35 36 35

(kg ha- ’ ) Avialable K 516 520 535 505

(kg ha- ’ >

trench planting (Fig. 5). Pod yields under all the treatments increased regularly from year to year and maximum yields were obtained in 1990-1991. The average pod production per hectare per year on a high pH soil was worked out to be 716 kg in trench, 758 kg in pit and 882 kg in augerhole planted Prosopis. Mean pod yields reported in the present study are less than the values cited in literature for many Prosopis species. Pod yields up to 140 kg per tree are reported (Felger, 1979; Felker et al, 1980). However, most of the work on Prosopis in the literature deals with pod yields from mature trees (Felger, 1979; Felker, 1979; Sharifi et al., 19821, whereas our yields are from young Prosopis stands.

3.7. Effect on soil properties

Prosopis plantations had a considerable ameliora- tive effect on soil properties (Table 7). However, the effect of site preparation methods on soil properties was not significant. The reduction was greatest in the surface (0- 15 cm) layer and decreased with depth to almost a negligible value beyond 45 cm. The ob- served decreases might have been mediated by root exudates and/or products of decomposition of tree and understorey litter. The sturdy and extensive root system of Prosopis also favours efficient salt leach- ing. The pH of alkali soils is highly sensitive to changes in the partial pressure of CO,. The CO, released from the roots of growing plants facilitates the replacement of absorbed Na in calcareous soils

by solubilising the native CaCO, (Goertzen and Bowers, 1958; Chhabra and Abrol, 1977), hastening the process of soil reclamation. Our other studies on tree plantations on alkali soils (Singh et al., 1989, 1990, 1992; Gill and Abrol, 1991; Singh and Singh, 1993) also showed that leguminous trees ameliorate high pH soils at a much faster rate than non-legu- minous ones.

The increase in organic carbon and available N may be owing to increased biological activity in otherwise dead mass of soil, through tree roots, litter fall and N fixation by Prosopis. Field studies else- where (Tiedemann and Clemmedson, 1973, 1986: Rundel et al., 1982) also found that soil under Prosopis canopies contains two to three times as much organic matter and N as soils away from Prosopis canopies. Similarly, studies in a California desert found that Prosopis produced 30 kg N ha ’ year- ’ when their crown covered 34% of the total land surface area. Rundel et al. (1982) suggested that up to 100 kg N ha- ’ year ’ might be fixed by Prosopis, given greater ground cover and better man- agement practices.

4. Conclusions

Alkali soils are generally dense with a compact and hard sub-surface layer or caliche bed (nodular or amorphous CaCO,) at lower depths which impose a physical impediment to root development. Upgrading the compact zone by modifying soil environment using appropriate site preparation techniques is a basic requirement for successful establishment of trees in alkali soils. The present long-term study has clearly shown that site preparation for planting Prosopis julijlora in the vertically downward direc- tion (breaking hard pan> was more beneficial than reclamation of surface layers in the horizontal direc- tion (hard layer not broken). The growth perfor- mance of Prosopis 8 years after planting was much better when the trees were planted in augerholes (15 cm diameter, 90 cm deep) than when pit and trench planting methods were used. Air dried biomass accu- mulated by Prosopis in 6 years was also maximum (36.2 t ha-’ 1 in augerhole and minimum (29.6 t ha- ’ 1 in trench planting. In the case of augerhole planting, Prosopis trees were able to extend their

G. Singh / Forest Ecology and Management 80 (1996) 267-278 277

root system beyond 2 m depth in 2 years whereas in pit and trench planting the roots were mainly con- fined to the surface 60 cm layer. Owing to better root development, augerhole-planted trees had higher lit- ter and pod production than pit- and trench-planted Prosopis. Prosopis growth caused significant reduc- tion in sodicity and improvement in fertility status of a barren alkali soil. These results indicated that nearly 3 million ha of abandoned alkali soils in India could be successfully utilised for raising Prosopis plantations using the augerhole planting technique, thus easing fuelwood shortages in the country.

Gill, H.S. and Abrol, I.P., 1991. Salt affected soils, their afforesta-

tion and its ameliorating influence. lnt. Tree Crops J., 6: 239-260.

Goertzen, J. and Bowers, C.A., 1958. Carbon dioxide from plant

roots as a factor in the replacement of adsorbed sodium in a calcareous soil. Soil Sci. Sot. Am. Proc., 22: 36-37.

Golley, F.B., Madina, E., Clements, R.G., Child, G.I. and Duever,

M.J., 1975. Mineral Cycling in a Tropical Moist Forest Ecosystem. University of Georgia Press, Athens, 248 pp.

Jackson, M.L., 1967. Soil Chemical Analysis. Asia Publishing

House, New Delhi, 458 pp.

Khan, M.A.W. and Yadav, J.S.P., 1962. Characteristics and af- forestation problems of saline alkali soils. Indian For., 88: 259-27 1.

Acknowledgements

Leaf, A.L., 1973. Plant analysis as an aid in fertilizing forests. In: L.M. Walsh and J.D. Beaton (Editor), Soil Testing and Plant

Analysis. Soil Science Society of America, Madison, WI, pp. 427-454.

The author is grateful to Dr. I.P. Abrol, DDG (Soil, Agronomy and Agroforestry), ICAR, New Delhi and Dr. S.S. Cheema, FACU, JOS C/o AD- PLA, 27 Dover Street, London for their guidance and encouragement during the planning and estab- lishment of this study. The author also wish to thank Dr. N.T. Singh, former Director and Dr. B.K. Khosla, Director, CSSRI, Kamal for their interest in and support of agroforestry programmes in the institute.

Lundgren, B., 1978. Soil conditions and nutrient cycling under natural and plantation forests in Tanzanian high lands. Rep. in

Forest Ecology and’ Forest Soils 31. Swedish University of Agriculture, Uppsala, p. 426.

Massoumi, A. and Cornfield, A.H., 1963. A rapid method for

determining sulphate in water extracts of soils. Analyst, 88: 321-322.

Pande, G.C., 1967. Afforestation of Usar lands. Proc. 1 lth All

India Silvicultural Conference, FRI, Dehradun, India. Rundel, P.W., Nelson, E.T., Shariti, R.A., Virginia, W.M., Jane],

D.H. and Shearer, G.B., 1982. Seasonal dynamics of nitrogen

cycling for a Prosopis woodland in the Sonoran desert. Plant Soil, 67: 343-353.

References

Bhargava, G.P., Sharma, R.C., Pal, D.K. and Abrol, I.P., 1980. A case study of the distribution and formation of salt affected soils in Haryana state. lnt. Symp. Salt Affected Soils, Kamal, pp. 83-91.

Bohm, W., 1979. Methods of studying root systems. Ecological studies. Springer, New York, 186 pp.

Chhabra, R. and Abrol, I.P., 1977. Reclaiming effect of rice grown in sodic soil. Soil Sci., 124: 41-45.

Felger, R., 1979. Ancient crops for the 21st century: In: G.A.

Ritchie @ditor), New Agricultural Crops. American Associa- tion of Advances in Science Symposium, Vol. 38, Westview Press, Boulder, CO.

Sandhu, S.S. and Abrol, I.P., 1981. Growth responses of E.

tereticornis and A. nilotica to selected cultured treatments in a highly sodic soil. Indian J. Agric. Sci., 51: 437-443.

Sharifi, M.R., Nilsen, E.T. and Rundel, P.W., 1982. Biomass and

net primary production of Prosopis glandulosa (Fabaceae) in the Sonoran desert of California. Am. J. Bot., 69: 760-767.

Singh, B., 1982. Nutrient content of standing crop and biological

cycling in Pinus patula ecosystem. For. Ecol. Manage., 4: 3 17-322.

Singh Gurbachan and Singh, N.T., 1993. Mesquite for the revege- tation of salt-affected soils. Tech. Bull. No. 18, CSSRI, Kar- nal, India, 24 pp.

Singh Gurbachan, Abrol, I.P. and Cheema, S.S., 1989. Effect of

irrigation on Prosopis julij7ora and soil properties of an alkali soil. lnt. Tree Crops J., 6: 81-99.

Felker, P., 1979. Mesquite-An all purpose leguminous arid land tree. In: G.A. Ritchie (Editor), New Agricultural Crops. Amer- ican Association of Advances in Science Symposium, Vol. 38,

Westview Press, Boulder, CO, pp. 89-132.

Singh Gurbachan, Gill, H.S., Abrol, I.P. and Singh, N.T., 1990. Agroforestry for improvement and management of salt af- fected soils. In: Proc. lnt. Symp. on Water Erosion, Sedimen- tation and Resource Conservation, CSWCR and Tl, Dehradun,

India, pp. 420-428. Felker, P., Clark, P.R., Osbom, J.F. and Cannell, G.H., 1980. Singh Gurbachan, Abrol, I.P. and Gill, H.S., 1992. Agroforestry in

Utilization of mesquite (Prosopis sp.) pods for ethanol pro- salt affected soils. In: P.K. Khosla (Editor), Status of Indian duction. In: Tree Crops for Energy Production on Farms, hoc. Forestry-Problems and Prospectives. Indian Society of Tree Workshop Solar Energy Research Institute, 14 November Scientists, Nauni, Solan, pp. 21 l-227. 1980, National Technical Information Service, Springfield, Singh, N.T., 1992. Dry land salinity in the Indo-Pakistan sub VA, pp. 65-78. continent. Paper presented at the International Conference on

278 G. Singh/ Forest Ecology and Management 80 (1996) 267-278

Degradation and Restoration of Arid Lands, Texas Technical University, Lubbock, TX, 24-25 September 1991.

Steward, H.T.L., Fhnn, D.W. and James, J.M., 1981. Biomass and nutrient distribution in radiata pine. In: Australian Forest

Nutrition Workshop, Productivity in Perpetuity, Canberra, Australia, pp. 173-185.

Szabolcs, I., 1977. Salinity and alkalinity of soil-extension classi-

fication and main properties. Proc. Indo-Hungarian Seminar on Management of Salt Affected Soils, CSSRI, Kamal, pp.

20-30.

Tiedemann, A.R. and Clemmedson, J.O., 1973. Effects of mesquite on physical and chemical properties of the soil. J. Range Manage., 26: 27-29.

Tiedemamt, A.R. and Clemmedson, J.O., 1986. Long term effects

of mesquite removal on soil characteristics: 1, Nutrients and bulk density. Soil Sci. Sot. Am. J., 50: 472-475.

Yadav, J.S.P., Bhumbla, D.R. and Sharma, O.P., 1972. Perfor- mance of certain forest species on a saline sodic soil. Proc.

Symp. New Development in the Field of Salt Affected Soils. ISSS, Cairo, pp. 683-690.