Development and Dissemination of 4R Nutrient Stewardship Knowledge to Support Crop Production Intensification in Western Kenya

The lack of appropriate site-specific nutrient management recommendations is a key contributor for low crop productivity in sub-Saharan Africa (SSA). The 4R Nutrient Stewardship Framework developed by the fertilizer industry aims to provide the context for efficient nutrient management focusing on four central components: applying the right fertilizer source, at the right rate, at the right time in the growing season and in the right place. To assess the impact of 4R practices in smallholder cropping systems, on-farm nutrient omission trials were initiated in 2013 in Western Kenya. The region has a high potential for agriculture intensification with current farmer yields being lower than 2 t/ha compared to research stations yields of up to 8 t/ha. The trials, implemented for two seasons, were established in 26 fields of varying soil texture and fertility levels. In each season, maize was planted at a spacing of 75 cm x 25 cm. N, P and K fertilizers were applied as urea, triple superphosphate (TSP), and KCl. All P and K fertilizers were applied at planting. Nitrogen applications were done in three equal splits at planting, three weeks after emergence and six weeks after emergence.

In both seasons, the NPK treatment resulted in highest average yields of 5.5 t/ha and 5.3 t/ha for the long rains (LR) and short rains (SR) seasons, respectively. This illustrated the importance of balanced nutrition in achieving and maintaining high yields. Current recommendations only cover N and P. Yield responses for N, P and K in the LR and SR seasons were 2.6 and 0.25, 0.4 and 2.5 and 1.3 and 0.7 t/ha, respectively. However, analysis of the agronomic efficiency (AE) of all the macronutrients for both seasons showed that long term omission of P and K from the system could adversely affect yields as the AE for N, P and K changed from 15, 13 and 11, respectively in the LR season to 17, 40 and 18 in the SR season. In both seasons, the unfertilized control yields were higher than the current farmer practice average yields, indicating that farmers are currently not applying the right agronomic practices such as the use of improved seeds, timely planting, weeding and plant spacing. The field sites were used to train farmer groups and extension agents about the 4R Nutrient Stewardship.