Inter cropping and population density effects on yield component, seed quality and photosynthesis of sorgum and soybean

Abstract

Population density and intercropping of sorghum (sorghum bicolour (L) and Soybean {Glycine max Merril (L)} may alter their growth and yield patterns through responses to light and physiological attributes as compared to their performance in standard densities and monocultures. There is limited field information on this hypothesis. Thus the objective of this study was to determine the influence of intercropping and population density on protein and oil yield components, photosynthesis of sorghum and Soybean at the canopy closure. The study was conducted at the University of Nairobi farm during the long rains. There was a significant increase in the number of Soybean pods per plant between the low density and normal density populations followed by a decline at high plant populations. Whereas population density increased the protein seed yield of Soybean, intercropping hardly altered it. In contrast, both population density and intercropping significantly decreased Soybean seed oil content. The observed protein and oil content is explained by the photosynthetic responses of partial shaded and fully exposed leaves. There was a significant decrease and increase of Soybean photosynthetic rates of both non-shaded and partially shaded leaves respectively within the intercrops, whereas population density caused a significant decline in non-shaded and partially shaded leaves. The interactive effects between population density and intercropping caused an increase in percent Soybean seed protein and decreases in its percent oil content and photosynthetic rates of partially shaded sorghum and Soybean leaves. These results demonstrate that population density and intercropping may be a viable alternative of manipulating the productivity of these crops through their changes in physiological processes