Improving Food Production by Understanding the Effects of Intercropping and Plant Population on Soybean Nitrogen Fixing Attributes

This paper quantifies the effects of population density and intercropping on the development and growth of nitrogen fixing attributes of soybean and explains how these attributes influence food through yielding process. Information for this study was obtained from a field study conducted over two rainy seasons comprising of the short and long rains in Kenya. Inoculated soybean was grown in two combinations; sole and intercropped with sorghum at three levels of population densities; 66, 666; 83, 333 and 111, 111 plants ha-1. Estimates of nodule mass, position, density, number, effective nodules and nodulation frequency were monitored at various intervals during the growing season. The responses of nitrogen fixing attributes of soybean varied with cropping pattern, density, stage of growth and the growing season. Intercropping caused decreases in nodule biomass at 21 days after planning (DAP), number of nodules, and nodulation frequency at the 1st, harvest of the 3rd season and at the 1st, 2nd and 3rd harvests of the 4th growing seasons. Significant increases in dinitrogen fixing attributes within intercropped stands were demonstrated for nodule position, percent effective nodules, and percent nodulation frequency at the 2nd and 4th harvests of the 3rd growing season. Influences of density on nodulation frequency during the 4th harvest were highly variable. Density and inter-cropping interactions caused significant decreases for nodule biomass at 21 DAP, percent nodulation at the 4th harvest during the 3rd growing in contrast to those decreases noted at the 2nd, 3rd and 4th only. The study indicates that for soybean yield, any management factors that cause a reduction in nitrogen fixing attributes are crucial to improving yield of soybean. There is therefore need to study the physiology of dinitrogen fixing attributes in order to understand yield processes. The Journal of Food Technology in Africa Volume 6 No.4, 2001, pp. 110-11