Implications of n, p, k, and npk combined on cassava (manihot esculenta crantz) root yield and soil nutrient status

In Nigeria, the ever increasing demand for cassava to meet the industrial and domestic needs of the people, has necessitated the need to accord cassava husbandry, more research attention in order to raise the present level of cassava yield on farmers’ farms. To partly meet this need, this study was designed to evaluate efficacy of N, P, K, and NPK combined in improving cassava root yield and soil fertility status. The experiment was laid out in a randomized complete block design with three replicates. The different nutrient elements included: N, P, K, NPK combined and control or check (C). The results obtained indicated existence of significant (P = 0.05) differences among the nutrient elements with respect to their effects on nutrient status of an Alfisol and cassava root yield. At the end of 2012 cropping season, nutrient elements significantly increased soil organic carbon (SOC) from 0.40 g kg-1 for C to 0.51, 0.59, 0.64 and 0.47 g kg-1 for N, P, K, and NPK, respectively. Similarly, at the end of 2013 cropping season, nutrient elements significantly increased SOC from 0.35 g kg-1 for C to 0.45, 0.54, 0.60 and 0.40 g kg-1 for the respective N, P, K, and NPK. At the end of 2012 cropping season, nutrient elements significantly increased total N from 0.35 g kg-1 for C to 0.46, 0.36, 0.35 and 0.41 g kg-1 for N, P, K, and NPK, respectively. At the end of 2013 cropping season, nutrient elements significantly increased total N from 0.32 g kg-1 for C to 0.42, 0.32, 0.33 and 0.37 g kg-1 for N, P, K, and NPK, respectively. Mean values of cassava root yield data across the two years of experimentation indicated that, nutrient elements significantly increased cassava root yield from 6.40 t ha-1 for C to 7.25, 6.90, 7.70 and 7.90 t ha-1 for N, P, K, and NPK, respectively.