Interaction of Nitrogen, Phosphorus, and Potassium and Their Effects on Biomass and Root Yield in Cassava.

Abstract Nutrient studies for cassava largely apply fertilizers through banding whereas, fertigation is rare. This study analysed the interaction among N, P, and K applied through an irrigation solution in cassava and the level at which they optimize growth and root yield. This was achieved by establishing three experiments in the greenhouse consisting of six concentrations of N, P, and K in a hand irrigation solution. Results showed that K regulated N and P accumulation in cassava leaves but not their uptake. It was also observed that P influenced N uptake and accumulation in cassava leaves more than N’s influence on P uptake and accumulation in the leaves. In addition, N above 70 mg l-1 and P above 20 mg l-1 had an antagonistic effect on K uptake and accumulation in cassava leaves. Maximum fresh and dry root weights were achieved at 100 mg N l-1, 20 mg P l-1, and 200 mg K l-1. Cassava had luxury P absorption after 20 mg P l-1, the concentration at which maximum yield was achieved, without symptoms of toxicity, an indication of tolerance to high levels of P. Linear increase of root weight as K concentration in the irrigation solution increased depicted K as the nutrient most limiting to root development. Keywords: macro-elements; root tuber; fertigation; irrigation; fertilizer; 1