Improving Sorghum Grain Yield Through Use Of Mineral Fertilizers And Farm Yard Manure For Smallholder Farmers In Makueni And Machakos Counties

ABSTRACT

Reduced food productivity in smallholder farms is the principal cause of food insecurity in semi-arid parts of Kenya. This is mainly attributed to decline in soil fertility, low and unreliable rainfall, land degradation and adverse effects of climate change. The solution lies in the efficient use of nutrients and planting of drought tolerant crop varieties that can cope with the low rainfall in the ASALs. The aim of this study was to evaluate the effect of FYM, mineral fertilizers and their integration on the production of Gadam sorghum and change in soil properties in Makueni and Machakos counties. The experimental design was a factorial arranged in Randomized Complete Block Design. The study consisted of two experiments in each site. The first experiment was a pure mineral fertilizer experiment with two factors (nitrogen and phosphorus) each at four levels (0, 25, 50, 75 kg/ha). The second experiment tested a combination of FYM (0, 5 & 10 tons/ha) and NP fertilizer in form of CAN and TSP, respectively, at 0 and 50kg/ha each. The first experiment involved 16 treatments while the second experiment involved 6 treatments. The results of grain yields in the first experiment were significantly different in the various treatments (p=0.02) at Kampi ya Mawe and (p=0.04) at Katumani. Nitrogen increased sorghum yields more than phosphorus, but not significantly. However, combining N at 75 kg/ha and P at 50 kg/ha gave the highest yields of 4859.1 kg/ha at Kampi ya Mawe, which was an increase of 135% above the control. At Katumani, combining 50kg/ha N and 25 kg/ha P gave the highest grain yield of 2485.1 kg/ha which was 68.3% above the control. In the second experiment, combining FYM with NP fertilizer at 50kg/ha NP and 10 tons/ha FYM gave the highest yield of 5393kg/ha compared to the control treatment (4233.1 kg/ha) at Kampi ya Mawe, which was 13.7% more. At Katumani, however, combining FYM and NP fertilizer had less yields as compared to the control. FYM at 10ton/ha and NP 50 kg/ha gave 1566.4 kg/ha which was not significantly different compared to 1669.4 kg/ha for the control. The amount of available N in the soil increased proportionately with N application and declined gradually throughout the growing season. Nitrogen uptake by sorghum also increased with increased N application while soil microbial population was increased with the application of FYM. Nitrogen use efficiency (NUE) was optimal at 50 kg/ha N and declined with increased application of N while Phosphorus use efficiency (PUE) was highest at 50 kg/ha P. Sorghum was more efficient in utilizing nitrogen than phosphorus. Based on the results, a combination of FYM and NP fertilizer can be recommended for sorghum production both at Kampi ya Mawe and Katumani. The findings of this study will be valuable in extension efforts towards increasing sorghum productivity and awareness by farmers of best ISFM practises in semi-arid eastern Kenya.