The nitrogen nutrition of yam (Dioscorea spp)

Information on the nitrogen (N) nutrition of yam (Dioscorea spp) is limited. Our objective was to elucidate the factors controlling N uptake by D. rotundata and D. alata. We analyzed results obtained with improved cultivars of these species grown in three field experiments among which N-15-fertilizer was used in one. Plant biomass production, leaf area index (LAI), root length density, N and N-15 uptake by the plant were measured in these experiments. Nitrogen uptake was controlled in both species by plant demand and N inputs. A positive relation was observed between N uptake and LAI. Despite the small root system, the ability of the plant to take N up was high. The amount of N derived from the fertilizer recovered in the plant was explained by total N uptake. Finally, avenues to improve the low nitrogen fertilizer recovery (<20%) in yam are discussed.