Effects of inorganic fertilizer applications on grain yield, nutrient use efficiency and economic benefits of maize in Western Kenya

Declining soil fertility levels due the application of low rates and unbalanced nutrients is the main cause of low yields in western Kenya. We therefore designed a randomized complete block nutrient omission trial with six replications to determine the effects of inorganic fertilizers on grain yield, nutrient use efficiency and economic benefits of maize in the region. The treatments were NK, NP, PK, NPK and NPK+CaMgZnBS. The results showed that application of PK fertilizer regime resulted in slow crop growth rate (CGR) and relative growth rate (RGR) and low biomass compared to other treatments. Application of a wider range of nutrients (NPK+CaMgZnBS treatment) improved maize growth and yield compared to other treatments. In terms of grain response, N application recorded the highest yield (1800 kg/ha) followed by P (1300 kg/ha) then K (1100 kg/ha) and least by a combined application of secondary macronutrients and micronutrients (ZnBMgCaS = 400 kg/ha). Highest agronomic efficiency of 32.5 kg grain /kg nutrient applied was recorded due to P followed by K (27.5 kg grain /kg nutrient) and least by N (15 kg grain /kg nutrient).. Economic analysis showed higher total production cost, gross revenue and net revenue due to application of NPK+ZnBMgCaS fertilizer than other treatments. However, the lowest (1.60) and highest (2.12) benefit to cost ratio values were recorded due to the application of PK and NPK fertilizer regimes, respectively. Based on this study, inclusion of Zn, B, Mg and Ca nutrients increased yield but it was not economical, indicating that farmers could be encouraged to apply a combination of N, P and K fertilizers.