Efficacy of Two Sulphur Fertilizers on Some Crops in Smallholder Farming in Kenya

In Kenya, smallholder farmer's production accounts for 75% of total agricultural output and 70% of marketed agricultural produce. However, productivity in the smallholder farms is still below potential due to continuous cropping with low and inefficient use of agricultural inputs, particularly fertilizers. Yields and fertilizer efficiency of high sulphur requiring crops such as maize, soybean and beans pulses could be improved by the use of appropriate sulphur fertilizers. Consequently, Kenya Agricultural Research Institute (KARI) in collaboration with OCP-Morocco initiated a three year multi-location on-farm trials to evaluate the efficiency of two OCP sulphur fertilizer formulations: NPS: 19:38:0:7S and NPS: 12:46:0:7S on maize, soybean and climbing beans. The field trials started in October and were conducted in 56 farms across four counties of Central Kenya. The trials design is randomized complete block (RCB) with farms in one cluster acting as replicates. Four treatments consisting of two OCP sulphur containing fertilizers (NPS), Diammonium phosphate and NP-23:23 were all tested against the farmer's practice (FP) on maize, soybeans and climbing beans. Results obtained indicated significant yield differences between treatments (P<0.05) within the counties. Majority of the sites exhibited crop responses to the different fertilizers but with large yield variations across the sites resulting from differences in soil fertility levels, sulphur status of cropped fields, crop management and rainfall/water regimes. However, these preliminary results from a single crop growing season will be compared with those from the next five seasons planned to be covered by the project. In the next cropping seasons the four fertilizers will be tested in presence and absence of lime. Soil sulphur status from analyses underway will be considered in the assessment of crop responses to the OCP NPS fertilizers.