1986) 131

E N G I N E E R I N G N E E D S F O R P O T A T O P R O D U C T I O N F R O M T R U E SEED~

Suhas R. Ghate , Casimir A. Jaworski, Sharad C. Phatak, and Ronald D. Gitaitis 2

Abstract

Potatoes grown from true potato seed (TPS) are generally small and nonuniform in size and shape, compared to the ones produced conventionally from seed tubers. Potato product ion from T P S would be considerably less expensive than from seed tubers because of the negligible storage and handling costs of the TPS. Potato product ion from T P S would therefore have the greatest potential in the developing countries. In developed coun- tries, this product ion method would have some potential in commercial product ion as well as in home gardening. Research related to the T P S potato product ion has been mostly directed toward investigating suitable cultural practices, screening breeding lines for higher yield and warm climate adaptability, weed control in the field, and other similar product ion areas. Research concerning mechanizat ion of T P S potato product ion has been limited. Engineering input to the T P S potato production, handling and storage needs considerable attention to develop practical and economi- cal practices. This paper highlights some research areas which the authors believe are worth investigating. Engineering research that is conducted at the Coastal Plain Exper iment Station related to the T P S potato product ion has been outlined along with future plans.

R e s u m e n

Las papas producidas a travds de la semilla botfinica (TPS) son generalmente pequefias y desuniformes en tamafio y forma, en comparaci6n con aquellas producidas convencionalmente a trav~s de tub~rculos-semillas. La producci6n de papa a trav6s de T P S seria considerablemente menos costosa que cuando se utilizan tub6rculos semillas debido al casi inexistente a lmacenamiento y a los costos m/nimos de operaci6n de la semilla botfinica. La producci6n de papa a travds de la semilla botfinica tendria por Io tanto el

1Supported by Hatch, State and USDA funds allocated to the University of Georgia College of Agriculture Experiment Stations. Presented at the 1985 Summer Meeting of the ASAE in East Lansing, MI. 2Associate Professor, Agricultural Engineering Department; Soil Scientist, USDA-AR8; Pro- fessor, Horticulture Department; and Associate Professor, Plant Pathology Department, University of Georgia Coastal Plain Experiment Station, Tifton, GA 31793-0748, USA. Accepted for publication November 19, 1985. ADDITIONAL KEY WORDS: Mechanization, seeder, harvester, mechanical aid, storage studies, potato handling, transplant clipping.

132 AMERICAN POTATO JOURNAl. (Vol. 63

mayor potencial en los paises en desarrollo. En los paises desarrollados este m6todo de producci6n tendria alg(ln potencial tanto en la producci6n comercial como en los huertos caseros. La investigaci6n relacionada con la producci6n de papa a trav6s de semilla bot~inica, ha estado mayormente orientada a investigar prficticas culturales adecuadas, a evaluar lineas de cruzamientos o mejoramiento para mayores rendimientos y su adaptaci6n climas calurosos, al control de las malas hierbas en el campo y a otros aspectos similares de la producci6n. La investigaci6n correspondiente a la mecanizaci6n de la producci6n de papa a trav6s de semilla botfinica ha sido muy limitada. E1 manejo y direcci6n de la producci6n de papa a trav6s de semilla botfinica, asi como su manipulaci6n y almacenamiento, requiere de considerable atenci6n para desarrollar procedimientos prficticos y econ6micos. Este trabajo pone de relieve algunos aspectos de investigaci6n que de acuerdo a los autores es importante investigar. Algunas investigaciones sobre el manejo de la producci6n de papa a trav6s de semilla bot~inica que estfin siendo conducidas en la Estaci6n Experimental de los Llanos Costeros, han sido descritos conjuntamente con algunos proyectos futuros.

Introduct ion

Potatoes are grown commercially from seed tubers. Good quality potato tubers are cut into several pieces each with an "eye" and then seeded into the soil for production. Generally, it takes about it to 2t of seed tubers to plant one ha of potato field. Production, transportation, handling and storage of seed tubers are expensive operations because they are bulky. In addition, the seed tubers should be completely free from any disease because an infested tuber can expose the entire field to the source of infection (20). The cost of potato seed tubers in the U.S.A. is about 20% of the total production cost while it could be as high as 30% to 50% of the total production cost in many other countries of the world (21).

True potato seed (TPS) are obtained from potato berries and are very small. The re are approximately 1.5 to 1.6 million seed per kg of the seed weight. It takes about 200 to 300 g of T P S to sow one ha of potato field. Storage, handling and transportation of the T P S are easy and inexpensive' ( 1, 9, 10, 11, 12, 18). Moreover, T P S can be stored for many years and does not get readily infected with viral, fungal and bacterial agents as seed tubers do. Using T P S for potato production can considerably reduce the cost of production ( l, 12).

However, the potato tubers produced from the T P S are nonuniform, varying from just a few g to several hundred g each. This product is therefore no match for the large uniform potatoes produced from the seed tubers. Because of the small and nonuniform size and shape, and other reasons such as length of growing season, potatoes from T P S have not been commercially produced in the U.S.A. and other potato producing countries. Neverthe-

1986) GHATE, et aZ" ENGINEERING NEEDS 133

less, due to the low cost of production, TPS is still a viable alternative for potato production in many countries of the world (9, 10, 13, 18). In the U.S.A. and other potato producing nations, TPS can be extensively used in commercial production of small tubers and in home gardening.

Researchers are working on the screening and selection techniques of TPS breeding lines which are suitable to various climatic conditions of the world including warm climates. Their research is leading to the selection of T PS lines which can produce large quantities of potato tubers (1, 9, 11, 12). Even though nonuniform size is a problem, high yields of tubers would substantially decrease the production cost, and if achieved, TPS could be considered as an attractive choice for some potato producing farmers.

Although research is currently being conducted related to TPS in the areas of its selection, production and cultural practices (7, 8, 12, 15, 16), there is not much research being done in the engineering areas such as mechanization and handling. The purpose of this paper is to outline some of the engineering needs related to the potato production from TPS.

Seeding Techniques

TPS can be used in three different ways to produce potatoes: (i) TPS is sown equidistant in rows and potatoes are produced similar to other vegeta- ble crops by direct seeding; (ii) TPS is sown to obtain thick stands in rows for transplant production (10, 13) and the plants are harvested after several weeks of growth and then transplanted in another field; and (iii) TPS is sown directly in a virus and insect free area in rows and small seedling tubers are produced. These small seedling tubers are then planted into the produc- tion area just like the seed tubers ( 10, 13, 22). Potatoes produced in this way are relatively more uniform and the final tubers are generally larger than the seedling tubers. Technique (ii) is similar to the one used in the production of several vegetable crops such as tomatoes, peppers and cabbage.

The seeding technique determines the appropriate seeder to be used. For direct seeding and for transplant production, small seeders using cone, disk and vacuum principles can be used. It has been demonstrated that germination of TPS before sowing improves plant stand of some breeding lines in warm climates (4). In this case, using a fluid drill is essential. In this method of seeding, germinated seed is thoroughly mixed with some carrier medium, typically a gel, and then the seed gel mixture is deposited into the soil furrow (5). Gel seeders may be based on a compressed air principle (Figure 1) or a peristaltic pump principle for seed gel extrusion (Figure 2).

Equipment is not available to seed small seedling tubers if the potatoes are to be produced from the third seeding technique mentioned above. A planter which can place these small seedling tubers at equidistant locations is necessary in order to produce potatoes from TPS in this indirect fashion. Either a new planter should be designed or an existing planter should be

134 AMERICAN POTATO JOURNAL (Vol. 63

FIG. 1. A compressed air fluid drill.

FIG. 2. A fluid drill using peristaltic pumps.

modified for this purpose. This technique would still be less expensive than the product ion from seed tubers even though both approaches appear to be similar. These seedling tubers are much smaller than conventional seed tubers. The i r storage and transportation would be less expensive than those

1986) GHATE, et al: ENGINEERING NEEDS 135

for the conventional seed tubers. In addition, this type of vegetative propa- gation is limited to a two season cycle {production of seedling tubers from T P 8 in one season and production of potatoes from seedling tubers in the next season or year) unlike the conventional method in which vegetative propagation continues for unlimited time.

Clipping

T h e second technique (ii) of T P S potato production requires growing and shipping potato transplants. These transplants would require clipping before shipment similar to the other vegetable transplants. T h e mechanical clippers used in the production of tomato or other vegetable transplants could be used for T P 8 potato transplant clipping but would not be ideal in commercial use. These clippers can transmit viral, bacterial and other diseases in tomatoes and other vegetable transplants. Potato is highly suscep- tible to many viral diseases, hence these clippers, even though widely used for other transplants, would not be suitable for potato transplants. It is necessary to design and construct a transplant clipper which would either eliminate or reduce the possibility of disease spread. Research related to potato production from T P S transplants would be greatly enhanced by the design, construction and use of a new clipper.

Harvesting

Because of the small size and nonuniformity of tubers, currently availa- ble potato diggers and harvesters are not suitable for harvesting potatoes grown from TP8 . Two different types of equipment or one with two attachments might be necessary. T h e potato harvester should harvest nonuniform marble-like seedling tubers (less than 10 g) for replanting if the third seedling technique described in the previous section is used. T h e same harvester should be able to harvest larger tubers either grown from seedling tubers or from direct sowing of the TP8 . These potatoes are small and nonuniform and the harvester should be able to pick them all. This machine may be a semiautomatic harvester or may be just a harvesting aid. Its use is anticipated only in small fields at this time.

Material Handling and Sizing

T h e potatoes produced from T P S are nonuniform and will require a considerable amount of sizing. A sizing station should be designed where potatoes as small as 2 cm in diameter can be easily sorted. These potatoes may have various ultimate uses. For example, the small potatoes can be used as salad potatoes or for canning, while the large ones can be used as fresh market vegetables and the odd sizes can be used by industries for making reconstituted potato products. The equipment should similarly be manually

136 AMERICAN POTATO JOURNAL (Vol. 63

operated, material handling aids because these will be used mostly on small farms.

Storage Studies

Storage studies related to potato transplants and final products are necessary if the potato production from TPS is to be commercialized. Some studies on transplant storage have been done (17). The results of these studies may be adapted to potato production from TPS if the TPS potato production follows the production patterns of several vegetables in the U.S.A.; e.g., growing transplants in warm areas and transporting them to cool areas for final production. Storage studies on the potatoes from TPS are necessary because of their small size and tender skin. The temperature, humidity and air circulation requirements for these tubers could well be different from the conventionally grown potatoes.

Physical Properties Studies

Determination of physical properties of any fruit, vegetable, nut, root or tree is essential whenever mechanization of its production is planned. Many studies have been conducted on tomatoes, apples, potatoes and several other products which are (or could be) machine harvested and are handled several times before reaching the consumer (2, 6, 14, 19). The seedling tubers or the potatoes produced from them can be used as a good quality product for consumption, as a salad product, or as a fresh market vegetable. Physical properties such as density, bioyield point (a stress level at which increase in deformation occurs with no change or decrease in force), hardness, skin texture, relaxation modulus (ratio of shear stress to shear strain at any time when the strain is kept constant), etc., should be studied as they have been in the case of many fruits and vegetables. These studies will provide valuable information which can be used to design handling equip- ment, mechanical aids, sizer, harvester and transportation containers.

Progress at the Coastal Plain Experiment Station

For the past several years, techniques for producing potatoes from TPS have been worked on. Considerable research has been conducted on screen- ing and selection of TPS for warm climates, best general cultural practices, and weed control studies (7, 8, 12, 15, 16). Even though engineering research has been limited, preliminary results are promising.

The performance of germinated seeds using the fluid drill designed at CPES has been investigated (4). In addition, the performance of TPS using pelleted seed with a precision Stanhay planter has been studied (7). Equip- ment has been designed and constructed (Figure 3) to mass inoculate potato plants in the field with Pseudomonas so/anacearum (3). Even though this

1986) GHATE, e t al." ENGINEERING NEEDS 137

FIG. 3. A mass inoculator for inoculating potato plants.

inoculator is not meant for use in potato production, it is extensively used in our potato research program to screen potato breeding lines which are bacterial wilt resistant and heat tolerant. It could also have applications in studying clones of potatoes grown from TPS.

We have modified a sweet potato harvester to dig small nonuniform tubers produced from TPS (Figure 4). The digging mechanism was only partially successful since separation of soil clods and very small stones from potatoes still remains a problem. A mechanical aid (Figure 5) has been designed which can be used to hand seed very small research plots. The same equipment can also be used to pick potatoes from the ground once they are dug and thrown back on the soil by the modified sweet potato harvester. Our future research plans include physical properties studies and develop- ment of a sizer for potatoes produced from TPS.

Summary

Production of potatoes from TPS would be considerably less expensive than from seed tubers. However, because of the small and nonuniform sizes of the TPS tubers, among other reasons, this production practice is not widely accepted. Engineering research concerning the TPS potato produc- tion is necessary to develop practical and economical production practices. Some of the engineering needs which the authors believe worth investigat- ing are (i) to develop seeders to sow TPS and to seed seedling tubers grown from TPS, (ii) to develop clippers to clip TPS grown potato transplants

138 AMERICAN POTATO JOURNAL (Vol. 63

FIG. 4. A modified sweet potato harvester for digging potatoes from TPS.

FIG. 5. A mechanical aid for handling farm products.

w i thou t t ransmi t t ing any viral or bacterial diseases, (iii) to design and cons t ruc t a harvester or a mechanica l aid to harvest all of the small and un i form T P S tubers, (iv) to cons t ruc t e q u i p m e n t for sizing and handl ing of small tubers, (v) to conduc t storage studies on small tubers, and (vi) to

1986) GHATE, eta/." ENGINEERING NFEDS 139

i nves t i ga t e phys ica l p r o p e r t i e s such as b i o y i e l d po in t , dens i ty , r e l a x a t i o n

m o d u l u s , m o d u l u s of e las t ic i ty , and sk in t e x t u r e of t h e smal l t u b e r s g r o w n

f r o m T P S .

Li terature Cited

1. Accatino, P. and P. Malagamba. 1982. Potato production from true seed. Bul Inter- national Potato Center, Lima, Peru, 20 pp.

2. Garrett, A.W., N.W. Desrusier, G.D. Kuhn and M.C. Fields. 1960. Evaluation of instruments to measure firmness of tomatoes. Food Tech 14:562.

3. Ghate, S.R., R.D. Gitaitis, S.C. Phatak and C.A. Jaworski. 1982. A field inoculator for potatoes. Trans Am Soc Agric Eng 25(4):919-920.

4. Ghate, S.R., C.A. Jaworski and S.C. Phatak. 1983. Emergence and plant stand of pregerminated true potato seed in warm climate. Am Potato J 60:557-562.

5. Ghate, S.R., S.C. Phatak and C.A. Jaworski. 1985. A new seeder for fluid sowing germinated seed. ActaHort (In Press).

6. Huff, E.R. 1967. Measuring time-dependent mechanical properties of potato tubers, equipment, procedure, results. Trans Am Soc Agric Eng 10(3):414-419.

7. Jaworski, C.A., S.C. Phatak and S.R. Ghate. 1985. Potato performance from high seeding rates of true potato seed under hot climates. HortScience 20:656 (Abstract).

8. Jaworski, C.A., S.C. Phatak, S.R. Ghate and R.D. Gitaitis. 1983. Potato transplant and tuber production at high seeding rates of true potato seed. Am Potato J 60:811 (Abstract).

9. Kim, K.K., H.Y. Kim and C.H. Song. 1983. Potato production by TPS in a temperate region. Proc International Congress. Research for the potato in the year 2000. Inter- national Potato Center (CIP), Lima, Peru. pp. 109-110.

10. Li, J.H. 1983. Prospects for the use of true seed to grow potato. Proc International Con- gress. Research for the potato in the year 2000. International Potato Center (CIP), Lima, Peru. pp. 17-18.

11. Martin, M.W. 1983. Field production of potatoes from true seed and its use in a breeding program. Potato Res 26:219-227.

12. Martin, M.W. 1983. Techniques for successfill field seeding of true potato seed. Am Potato J 50:245-259.

13. Monares, A., P. Malagamba and D. Horton. 1983. Prospective systems and users for true potato seed in developing countries. Proc International Congress. Research for the potato in the year 2000. International Potato Center (CIP), Lima, Peru. pp. 134-136.

14. Nelson, C.W. and N.N. Mohsenin. 1968. Maximum allowable static and dynamic loads and effect of temperature for mechanical injury in apples. J Agric Eng Res 13(4): 317-329.

15. Phatak, S.C., C.A. Jaworski and S.R. Ghate. 1983. Weed control in transplant production from true potato seed. S Weed So Proc: 164.

16. Phatak, S.C., C.A. Jaworski and S.R. Ghate. 1985. Daminozide protects potato seedlings from metribuzin injury. HortScience 20(4):690-691.

17. Risse, L.A., C.A. Jaworski, S.C. Phatak and S.R. Ghate. 1984. Effect of storage tem- perature and duration on quality and survival of potato transplants. Am Potato J 61:261-265.

140 AMERICAN POTATO JOURNAL (Vol . 63

18. Sadik, S. 1983. Potato production from true seed--present and future. Proc International Congress. Research for the potato in the year 2000. International Potato Center (CIP), Lima, Peru. pp. 18-25.

19. Somers, G.F. 1965. Viscoelastic properties of storage tissue from potato, apple and pear. J Food Sci 30(6):922-929.

20. Thornton, R.E. and J.B. Sieczka (Eds.). 1980. Commercial potato production in North America. Potato Association of America Handbook. Supplement to Vol. 57 of the Am Potato J.

21. Van der Zaag, D.E. and D. Horton. i983. Potato production and utilization in world perspective with special reference to the tropics and sub-tropics. Potato Res 26:323- 362.

22. Wiersema, S.G. 1983. Evaluation of technology for production of seed tubers from true potato seed. Technology Evaluation Series No. 1982-1, International Potato Center (CIP), Lima, Peru.