Evaluation of nutrients uptake and partitioning in two yam (Dioscorea spp.) species

摘要

Nutrient uptake and partitioning in two yam species (Dioscorea alata and Disocorea cayenensis-rotundata) grown under different agro ecological zones (forest and savannah) were examined. Yams of both species grown in the forest took up much more nutrients (N, P, K, Ca, and Mg) than in the savannah. Significant differences were also observed between species. Nutrient contents based on dry matter in D. alata were about five times higher than in D. cayenensis-rotundata. At the whole plant level, uptake of N and K increased rapidly with plant age. Uptake of Ca also increased with plant age but reached a plateau from 103 to 163 days after planting (DAP) and decreased during the rest of the growth cycle. Uptake of Mg and P was low and almost constant during the entire growth period. The amounts of nutrients stored in the above ground biomass increased up to 103-140 DAP and decreased to nil one two months later as they were transferred to tuber and lost due to senescence. Conversely, the amount of nutrients stored in the tubers steadily increased from tuber initiation (76 to 103 DAP) until harvest time (194 to 220 DAP).