This formula, which has been used also in Trinidad by Henry (18) , 

 yielded 21 to 22 tons per hectare. 



A yield of 15 tons per hectare was obtained in ferralitic acid 

 soil (pH 4.3) of Guadeloupe with 120-120-150 kilograms N-P-K 

 or a 120-120-300 kilograms N-P-K, whether or not lime was ap- 

 plied. But application of 4 tons of powdered calcareous rock per 

 hectare the following year with the 120-120-300 N-P-K formula 

 raised the yield to 32 tons per hectare. 



The effect of type of planting material on vegetative growth 

 and yields has been studied by Ferguson, Haynes, and Springer 

 (16), Mathurin and Degras (28) y and Degras, Mathurin, and 

 Suard (13)- Growth of the plant is closely related to the nature of 

 the seed piece. The most common planting material is small, whole 

 tubers, but these are the most likely to be affected by disease. 

 Large tubers can be cut into several pieces. 



When the pieces are large, a difference in sprouting behavior 

 is observed, correlated with the part of the tuber used. Pieces taken 

 from the upper portion of the tuber (head pieces) germinate more 

 readily and produce more stems and tubers than do pieces from 

 the lower portion or whole tubers. However, yields are not always 

 affected by source of tuber piece, if sizes are equal. Tubers can be 

 cut into pieces as small as 5 grams, and when protected by a fungi- 

 cidal dip (benomyl) ,^ can be germinated satisfactorily. These small 

 pieces germinate late, in spite of differences in origin. Small pieces 

 are useful for multiplying a stock rapidly. 



Spacing trials in Trinidad (18) and Guadeloupe (2) showed 

 that as spacing decreases, yields decrease proportionally. This re- 

 sult would be expected because closely spaced plants compete with 

 each other. A spacing of 0.5 by 0.5 to 0.8 by 0-8 meters (40,000 to 

 15,000 plants per hectare) is recommended for maximum yields. 



At the time of planting, the seed piece is buried in the loose 

 soil of the hill or ridge to a depth several times its diameter. After 

 planting, the hills should be kept somewhat moist. Unless the tuber 

 piece is desiccated or small, germination occurs within a few weeks. 



It is also possible to plant from seed. Seeds should be stored 

 under dry, cool conditions and planted in clean soil with good 

 drainage and aeration. The young plants are delicate and should be 

 maintained in the nursery until twining stems arise. For conven- 

 ience, such seedlings can be transplanted from the seedling flat to 

 pots, for they transplant readily. When seedlings are transplanted 

 to the field, they need some care until they become well established. 



A variable degree of success has been achieved in the propa- 

 gation of D. trifida from stem cuttings (15)- Factors influencing 

 success include clone, age of stem, and position of cutting on the 



3 Methyl 1- (butylcarbamoyl) -2-henzimidazolecarbamate. 



16 



