Crop Yields and Returns under Different Soil Moisture Regimes

Abstract

Reserch begun in Kenya in 1977 under the Dryland Cropping Systems Research Project is described. In Machakos District, intercropping of maize and beans [Phaseolus vulgaris] was studied under line source irrigation. Yields of both spp. increased linearly with applied water until requirements were satisfied at 250 mm for beans; maize water requirements were not satisfied at 438 mm and the estimated water requirement for max. yield was 589 mm. With 450 mm water yields were 5.92 and 2.5 t/ha for pure strands of maize and beans, resp., compared with 4.98 + 0.7 t in the intercrop. Intercropping was only advantageous when rainfall was more than 325 mm with an early onset of rains. In a 2nd trial at Katumani maize yields increased with application of 40 kg N/ha, but higher rates did not increase yields further. In fertile conditions, grain production began when water use was 218 mm, but without N fertilizer 298 mm was required. Grain production also depended on plant density; with 154 mm rainfall plots of 20 000 plants/ha produced grain but higher density plots did not. In better rainfall seasons 40 000 or even 60 000 plants/ha produced max. grain yields.