Effects of NPK Fertilizer on Tuber Yield, Starch Content and Dry Matter Accumulation of White Guinea Yam (Dioscorea rotundata) in a Forest Alfisol of South Western Nigeria

SUMMARY Field trials designed to investigate the effects of nitrogen, phosphorus and potassium on the yield, starch and dry matter content of white guinea yam were conducted over a four year period in south western Nigeria. The optimum level of nitrogen for successful production of white guinea yam was 35 kg ha −1 in a forest Alfisol that had been under cultivation for at least two years. Nitrogen, phosphorus and potassium had no significant effect on starch content, but large applications of phosphorus and potassium significantly decreased dry matter accumulation.