Assessment of competition for water between Cassia siamea lam. and zea mays l. using various parameters, in alley cropping under Semi-arid conditions in Machakos District

Abstract

A study was carried out in Machakos district, Kenya, to investigate the competition for soil moisture in an alley cropping agroforestry system. The effects on soil moisture and crop yields of Agroforestry (AF) and Non-agroforestry (NAF) systems was evaluated in two growing seasons (Experiment 1 and 2). The AF system involved alleys of a perennial shrub, Cassia siamea Lam. and between them a crop Zea mays L. var. Katumani composite B. The AF system lopped plots were mulched with leaves and twigs from the Cassia hedgerows just before planting. Below The NAF plots were not ground interaction mulched. was determined by measurement of soil moisture using the gravimetric method. The soil was sampled using an auger, at four points of 45cm interval from the hedgerow and three depths for every point, respectively. Measurements of stomatal resistance, transpiration rates and leaf-air temperature difference were used as above ground indicators of competition for soil moisture, and therefore water stress. These were measured everyone or two weeks. The influence of distance from Cassia hedgerows on soil moisture did not prove significant for the first - xix - five measurements of experiment 1 and for the entire set of measurements of experimend 2, for all depths. There was no interaction between AF system and distance or depth. Stomatal resistance of the middle maize row (MMR) was not significantly different from that of the border maize row (BMR) in the AF system for both experiment 1 and 2, respectively. Stomatal resistances of the AF system maize plants were generally lower and in some cases also statistically significantly different from those of the NAF system maize plants for both experiments. Transpiration rates of maize within the AF system showed statistically insignificant variation between the MMR and the BMR. AF system maize plants showed generally higher transpiration rates than the NAF maize plants, which were again in some cases even statistically significantly different. Leaf-air temperature differences of the MMR were not significantly different from the BMR in the AF system for both experiments. Appreciable differences were also not detected between AF and NAF systems for both experiments. Maize yield was not suppressed by proximity to the Cassia hedgerows. On the contrary, the grain and cob weights of the BMR were on the average significantly higher than those of the MMR for both - xx - experiment 1 and 2 probably due to a combination of factors such as soil temperature variation and differences in root overlapping. Maize in the AF system performed better than in the NAF system for both experiment 1 and 2, due to various improved conditions. The study showed that competition for soil moisture between Cassia and maize was not significant. This will have been due to the above average period.