Nutrient use efficiency of cassava differs with genotype architecture

Five cultivars each from tall, medium and short-stemmed cassava germplasm at CIAT were grown under rainfed condítions in inceptisols wíth adequate N, P and K fertilizer. Sequentíal harvests were made at 2, 4, 6 and 10 months after planting to determine LAl, top and root biomass production. At final harvest, N, P, K, Ca and Mg uptake in top and root biomass was determined. In both medium and short stemmed cultivars, LAI and top biomass were signiñcantly lower than in the tall cultivars. Differences in root yield were less pronounced due to higher harvest indices in medium and short-stemmed cultivars. Total nutrient uptake was also smaller in medium and short-stemmed cultívars due to lower top biomass. Nutrient use efficiency for root production was significantly greater in medium and short-stemmed cultivars as compared to the tall ones. It would be beneficial, therefore, to breed for short-stemmed cassava in order to reduce soil nutrient depletion and hence conserve soil fertility wíthout sacrificing yield potential. Moreover, due to the feasibility to increase pcpulation density with short-stemmed cassava, soil erosion in cassava-based cropping systems could be minimized because of early ground cover.