The effect of push-pull management and different fertilization strategies on maize crop yield in central Kenya
Abstract: The high population pressure in central Kenya has lead to continuous cultivation with minimal application of nutrient, resulting in nutrient depletion. A study was conducted to determine the effect of 'Push-pull' (intercropping maize with desmodium and napier grass) strategy management and nitrogen application on maize grain yield and soil fertility on smallholder farmer’s fields in three districts of central Kenya highlands. The experiment design was a split plot design with two factors ('Push-pull' vs monoculture and manure (5 t/ha) only vs manure and fertilizer (40 kg/ha) replicated in three areas with a total of 24 farms in central Kenya. Soil and plant samples were analyzed for macro-nutrients and micro-nutrient at the beginning and end of the season. The quality of fodders and manures was tested by measuring crude protein and fibre content, ash content and dry matter content. I found an increase in maize yield in 'Push-pull' fields compared with monocultures with only manure added (5t/ha) and the yield increased even more with modest application of fertilizer (40 Kg N/ha) combined with manure (5 t/ha). The average maize grain yield in "good" farms (i.e. both manure and fertilizer added) with 'Push-pull' cropping system was 186.4, 86.46 and 49.79 percent above the yield in, monocultures and 'Push-pull' in field with only manure, and monoculture in "good" farms respectively. There was strong significant difference (p<0.001) on maize grain yield between 'Push-pull' (5.52 t/ha) and monoculture (1.93 t/ha) cropping systems in the three districts of central Kenya. However, there was significant difference (p<0.05) on major soil and manure nutrients between good and poor farmer’s categories. The reduced maize yield (between 5.52 t/ha-1.93 t/ha) was due low rainfall distribution and different fertilization strategies between farmer’s categories during short rains of 2008. From management perspective, the different fertilization regimes had strongest positive effect on maize yield in well managed 'Push-pull' cropping systems.
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