Maize productivity and nutrient use efficiency in Western Kenya as affected by soil type and crop management

Low soil fertility and high weed infestation are the main culprits for the declining maize production in Western Kenya. Technology packages to address these constraints exist, but their effectiveness is likely to be influenced by variability in soil types and farm management practices in the region. Trials were conducted during the 2008/2009 cropping seasons to investigate the nutrient use efficiency and yield response of maize to some recommended management options for smallholder farmers on three dominant soil types of Western Kenya namely Acrisol, Nitisol and Ferralsol. Irrespective of seasons, average maize yields were highest on Nitisol (3.6 t ha-1) and lowest on Ferralsol (2.1 t ha-1). Maize yield gaps (difference between potentially achievable and actual yields) differed by season and soils with 4-5 t ha-1 on Nitisol and about 6 t grain ha-1 on Acrisol and Ferralsol. On Nitisol, the largest share of this yield gap (80%) was closed by the addition of mineral fertilizer, while on Ferralsol, reduced tillage could close 25-60% of the yield gap. The highest agronomic (13-39 kg grain kg-1 N) and physiological (50-160%) N use efficiencies were obtained with mineral fertilizers, while the addition of organic amendments resulted in the highest P use efficiency (15-154 kg grain kg-1 P), irrespective of soil type and season. As soil types and management options differentially affect yields and nutrient use efficiency of maize, there is a need for field-specific targeting of technologies to address maize production constraints in Western Kenya.