In Mayagiiez, P.R., mineral fertilizer supplements have not pro- 

 duced yields greater than those obtained with organic materials. 



Care 



Soon after the pieces are planted, the vines appear. They climb by 

 twining and need support for maximum growth. Any stake that permits 

 growth up to about 2 meters is adequate. Plants used as supports 

 compete excessively with the yams and reduce yields. Although some 

 varieties of yams can produce adequate yields without staking, lesser 

 yam tubers from unstaked plants seldom reach an adequate size. Poor 

 yield is closely associated in this case with poor vine development. 



In Cameroon, D. dmnetorum is usually not staked, but when it is 

 staked, it yields more. In Guadeloupe, a staking trial gave the follow- 

 ing results: 



Yield 



Method (tormes/hectare) 



No stakes 18.9 



Stakes of 1 meter 25.7 



Stakes of 2 meters 24.6 



Apparently, in this species even a 1-meter stake is sufficient to provide 

 the sunlight needed. In another experiment, staking affected not only 

 total yield but also dry-matter accumulation, especially in the final 

 months of growth, as seen below: 



Dry-matter percentage of D. transverssi tubers 



Growth (months) 



6 7 8 9 10 11 



No staking 25-28 23-28 22-29 29-30 29-30 30-32 



With staking 23-26 23-26 27-28 29-31 29-36 34-37 



During a drought, irrigation should be used. Long dry periods 

 will restrict the growth of the foliage and subsequent tuberization. 

 Drought during the last month of the growing season will limit growth 

 severely. D. transversa seems to withstand drought better than D. 

 alata cultivars. 



Little information is available on the diseases and pests of the minor 

 yams. At Mayagiiez, P.R., such yams have never been treated for 

 diseases and insects. In Guadeloupe, D. transversa 'Wael' has proved 

 resistant to anthracnose but slightly susceptible to a yam virus com- 

 plex. When disease and pest problems occur, literature on the major 

 yams should be consulted. 



Harvest and Yields 



As with most yams, the minor species are harvested after the vines 

 die back, usually at the end of the rainy season. The technique of 



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