Effects of nitrogen fertiliser and bean (Phaseolus vulgaris L.)

Abstract

The effects of N rates 0, 25, 50, and 100 kg N/ha and bean residue on the performance of beans (Phaseolus vulgaris L.). Mwezi Moja) in different cropping systems with maize (Zea mays L.) were studied on a sandy clay loam (dystric Nitisol) at Kimutwa and a sand (Acrisol) at Masii, both sites being in a semi-arid area. Fertiliser N significantly increased bean seed yields by up to 1.08 ton/ha in sole cropping, 1.45 ton/ha in rotation and 0. 55 ton/ha in intercropping thus indicating that N was deficient in the soils. Generally, bean seed yield response to N was quadratic, except in a few cases which were linear where bean residue was not removed from the plots. The highest response occurred in rotation probably because of depletion of N by the preceding maize crop while the least was observed in intercropping rate with the highest bean response in continuous sole cropping and those in alternate rows was 50 kg N/ha, but for those in rotation it was 75 kg N/ha while for beans in the same rows with maize they were 75 and 100 kg N/ha at Kimutwa and Masii, respectively. Greater yield response to N occurred in the Acrisol than in the Nitisol Number of pods/plant and relative yields (RYs) were not significantly affected by N. Intercropping significantly lowered number of pods/plant, seed yields and RYs. Beans intercropped in the same row with maize gave significantly higher seed yields and RYs than those in alternate rows. Beans in rotation gave significantly higher seed yields than those in sole cropping and intercropping systems. Return of bean residue significantly reduced seed yields and tended to lower the number of pod/plant. Higher seed yields were obtained during the Long Rains than during the Short Rains at Kimutwa while the reverse was true at Masii.