Plant nutrient aspects of mulch incorporation in alley cropping trials of semi-arid Machakos, Kenya

Abstract

Experiments on plant nutrient status and yield of maize in relation to mulch nutrient composition were conducted at Katumani, in Machakos district from 1987 to 1989. In all the seasons, Katumani B Composite was sown, apart from short rains of 1988,when hybrid 511was planted. Cassia siamea had been grown as the tree species forming the hedges. Between the hedges, 3 maize rows were sown parallel to the hedges. The hedges were lopped periodically at a height of 50 em and the loppings fully incorporated into the soil within the hedges (alleys) before the beginning of each season. In the control plots, each hedge row was replaced by a row of maize and no mulch incorporated. Nutrient analysis was performed primarily for macronutrients N,P,K,Ca and Mg for Cassia loppings, maize leaves, maize grains and maize stovers. Maize yield (grains) in g/row and weed biomass were also assessed. Decomposition for Cassia siamea loppings using standard litter bags was also monitored. The results indicated that incorporation of mulch increased the nutrient concentrations of maize leaves, grains, and stovers as revealed by higher levels of nutrient concentrations in the treated plots relative to the controls. Although there was a relatively higher yield in the treated plots as compared to the controls on per row basis, the differences were not significant. The weed biomass in the treated plots was more than in the control plots. Decomposition experiments indicated that approximately 70-90% of Cassia mulch dry matter could be lost within 60 days