Mixed copping of maize with beans with special reference to relative times of planting of the two crops in Western Kenya
Previous research, on mixed cropping experiments in the tropics cited in the literature review indicated clearly that the system i3 of great importance to the small farmers who would benefit greatly from improvements applicable to intercropping systems. In almost all of them the yields per unit area have shown some advantage from the mixtures compared to those from the pure stands of either crop* The main objective of these experiments was to study the effect of mixing maize with beans crops on their respective yields. Additional information was sought on the effects of different time of inter-planting, of plant arrangement and of labour inputs required. This thesis was therefore designed to provide this information. Mixed cropping conducted during "1974-1976 with special reference to relative times of planting of the two crops in Western T enya are described. In all experiments, maize densities were the same in pure 3tonds and mixtures and beans were added as a fraction of the pure stand densities. The results showed that the total yields of maize-bean mixtures per unit.area of land were - 2 - considerably higher than those obtained from the tv;o crops grown separately. This ’was found to be so in each season. Late planting significantly reduced the yields of beans in all years and of maize in 1976 when time of maize planting was included as a treatment* Intercropping maize with beans led to a small increase in the maize grain yields, but to a reduction of bean seed yields. The presence of beans therefore maintained high yields of maize in the mixtures as compa.red to controls and there was a significant increase in one year. In the first year of experiment (1974) maize yield from the mixtures seemed to have been higher than those -ftom the pure stands though not significantly different. Bean yields from the mixtures were significantly lower than the pure stands. The total yield of maize-bean mixtures per -unit area was higher than from monoculture. These trends were similar at the two sites, Kakamega and Bangalo. A second experiment which was conducted in 1975 at Kakamega indicated that there was an apparent yield advantage in maize-bean mixtures when these were planted at the same time. There were no bean yields from the treatments where beans were inter-planted, after the first weeding of meiae (20 days from the date of planting)# The bean yield was not affected by the crop arrangements became the beans planted in maize rows gave the same yield as the beans planted between the maize rows. In the 1976 experiments, the total yield production of mixed crops per unit area was higher than that obtained from monoculture of either crop, Tirae of planting of beans relative to maize was a very important factor for bean yields but not for maize yield. In 1976, the bean yielhf were greatly lowered by late planting especially at Kakamega site due to the incidence of damping off disease on the beans resulting in a low bean stand count. The reduction of pod number due to their abscission was another primary cause of the lower yield of beans. Inter-planting maize in the growing beans was not found advantageous in the system, but inter-planting beans after 5 days from the date of maize emergence was found to be very suitable for both crops. Planting these crops at the same was also found to be suitable especially for the bean crop. - 4 - It is suggested that breeders should select for a bean variety which is resistant to pod abscission for the success of bean yields in » this cropping system. Significantly less labour input was required in the planting and weeding operations in the pure maize stand compared with beans or with mixtures. However, the cash gross returns from this treatment was significantly lower than that from the mixtures. The advantage of cash gross retiurns from the mixtures per unit area decreased with the delayed time of planting. It is suggested that further work on labour input for the whole cropping period should be carried out under the sane environmental conditions to give more information on the economy of this cropping system. It is concluded that maize-bean mixtures planted early either at the same time or beans inter-planted at the emergence of maize is found to be a highly productive and profitable cropping system for the small farmers of Western Kenya.