Enhancing the Capacity for Dissemination of Site-specific Maize Production Intensification Technologies under Variable Farm, Climatic and Soil Fertility Conditions in Kenya and Zimbabwe

This project was implemented in collaboration with the International Centre for Maize and Wheat Improvement (CIMMYT) and the Kenya Agricultural and Livestock Research Organization (KALRO-Embu) to address knowledge gaps on the influence of farm, soil fertility variability and tillage system on maize production intensification potential in Eastern Kenya. The main objectives of the project are to: 1) synthesize information on farmer typologies, based on access and use of nutrient inputs and other socio-economic characteristics; 2) analyze yield gaps linked to farm typologies and rainfall variability and provide guidelines for site-specific maize production intensification; and 3) apply the Nutrient Expert® (NE) decision support tool analyze the agronomic and economic impact of nutrient management scenarios for various categories of farmers.

Farm surveys and soil fertility analysis were conducted to analyze the main determinants of fertilizer use by smallholder farmers in Eastern Kenya and their influence on soil properties. Based on the results, 40 farms were selected to host nutrient omission trials (20 conventional tillage and 20 reduced tillage). On each farm, five treatments (NPK, NP, NK, PK and a control) were laid out on plots measuring 5m by 5m. Nutrient application rates were 120 kg N/ha, 60 kg P/ha and 60 kg K/ha. Yield data for two consecutive seasons showed that the NPK treatment had the highest grain yield of 6.5 t/ha irrespective of the tillage system, indicating the need to add K to the current N and P recommendations. The overall performance of the treatments was in the order NPK ≥ NP > NK > PK > Control. Nitrogen was the most limiting nutrient, accounting for >60% of the yield response, followed by P. Potassium was only found to be limiting in some selected farms. The effect of tillage on maize yield and yield response to specific nutrients was not significant, likely due to the short-term nature of this study, and the long-term nature to transform soil properties with changes in tillage system. The data was used to calibrate the NE for Maize, Kenya version and was completed in 2015. Field validation of the Kenya NE version showed good performance of NE recommendations, which increased yields by about 1.2 t/ha and profits by US $250/ha compared to farmer practice. NE will be used to scale site-specific fertilizer recommendations in collaboration with the Ministry of Agriculture in 2016.