Effect of controlled release urea on soil nitrogen mineralization and maize yield in Siaya County, Kenya

Although nitrogen (N) is a major limiting nutrient in most soils in Kenya, it is often lost before it is used up by crops. This is due to the high dynamics of its transformations in the soil, making it easily lost from the soil. This usually leads to reduction in crop yield and environmental pollution through contamination of underground water resources. Appropriate management of soil fertility is key in realizing increased food productivity in Kenya with minimum environmental pollution. Controlled release urea fertilizers are one such strategies. This study investigated the N mineralization and yield of maize when using normal urea (NU) or controlled release urea (CRU) under conservation agriculture (CA) or conventional tillage in Siaya County. The experiment was superimposed on a long term trial with tillage system as the main plot and urea type as the split plot. Results showed significantly (P=0.05) lower nitrate concentrations with CT+CRU and CA+NU in the early stages of the season. Maize yields were not influenced by the urea type but were higher in conventional tillage systems than in conservation agriculture systems. More repeat studies are however necessary before conclusions can be made on the potential for CRU to reduce soil nitrate concentrations in Kenya.