EFFECTS OF INORGANIC FERTILIZER APPLICATION ON GRAIN YIELD, NUTRIENT USE EFFICIENCY AND ECONOMIC RETURNS OF MAIZE IN WESTERN KENYA

Abstract

Declining soil fertility levels due to application of low rates and unbalanced nutrientsis one of the main causes of low yields in western Kenya. We therefore designed a randomized complete block nutrient omission trialwith six replications to determine the effects of inorganic fertilizers on grain yield, nutrient use efficiency and economic returns 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 short plants, slow crop growth rate (CGR), and relative growth rate (RGR), small leaf area 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 macro and micronutrients (ZnBMgCaS = 400 kg/ha). Highest agronomic efficiency of 32.5 kg grain /kg nutrient applied was recorded due to Pfollowed 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 fertilizerthan 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 yields but was not economical. Therefore, farmers could be encouraged to apply a combination of N, P and K fertilizers only for better return on investment.