Biomass production and nutrient uptake of taro roots.

Abstract

Information on biomass production and nutrient uptake of roots in tropical tuber crops is scarce. In this paper data are presented on nutrient uptake of taro roots (Colocasia esculentaj in relation to corm yield and above ground biomass on a Typic Tropofluvents in the humid lowlands- near Lae. Fertilized (100-50-100 kg NPK ha'1) and unfertilized plants (n=4 each) were harvested at 126 days after planting (126 DAP=mid-season) and 231 DAP (harvest). Root biomass at 126 DAP was 0.26 t ha'1 (15% of total biomass) in the unfertilized plots and 0.52 t ha'1 (13% of total) in the fertilized plots but at 231 DAP root biomass was similar (~0.50 t ha'1). Root nutrient concentrations at 126 DAP was similar in both plots but N, Ca and S significantly declined in the unfertilized plots at 231 DAP whereas B increased with 18 mg kg'1 (p<0.01). In the fertilized plot P, K, Mg, Mn and Cu had decreased at 231 DAP but Zn had significantly (p<0.01) increased. Nutrients in the root biomass as a fraction of the total nutrient uptake were similar at 126 DAP for both treatments. At 231 DAP, however, the fraction of nutrients in the root biomass was considerably lower in the fertilized plots. Nutrient uptake by roots at harvest was 5 kg N, 1 kg P, 25 kg K, 5 kg Ca, and 3 kg Mg ha'1 for both fertilized and unfertilized conditions. The study has shown that taro roots contain considerable amount of nutrients but that a much larger proportion of plant nutrients is allocated to the roots under unfertilized conditions.