Growth And Yield Of Sorghum-Soybean In Relation To Density And Intercropping

Abstract

The study was aimed at determining the effects of intercropping and planting density on yield and growth parameters, photosynthesis and related processes, as well as, nitrogen fixation by soybean. The development of a predictive model based on combination of agronomic and physiological characteristics of both sorghum and soybean was tried. This study was carried out for four growing seasons in both field as well as greenhouse conditions. The crops were grown at three densities either as monocultures or intercropped. Growth, development and yield were measured during the growing seasons using destructive sampling and classical growth analysis. A number of physiological parameters were also monitored to understand the physiological basis for the observed patterns of growth, development and yield. Increasing plant density caused significant increases in sorghum grain yield during the 1st and 3rd growing seasons; LAR, SLW, NAR, shoot - root ratio, height,stem dry weight, photosynthesis, gs and transpiration at certain growth stages. Intercropping significantly increased grain yield of sorghum during the! 3rd and 4th growing seasons, in contrast to a decline during the 1st season, also photosynthesis increased with increasing light intensity. Intercropping sorghum caused a decline in height, LA, root dry weight, photosynthesis, g, and transpiration during moisture and light stresses. Intercropping soybean significantly reduced grain yield during the 1st and 2nd seasons; oil content, leaf numbers, LA, photosynthesis, gs transpiration and ARA at certain growth stages. Increase in planting density significantly increased grain yield of soybean during the 1st, 2nd and 3rd growing seasons; per cent protein, LA, leaf dry weight, per cent stem dry weight of soybean at certain growth stages Yield as well as growth attributes were examined in tenus of how density and intercropping caused changes in environmental resources of light, water and nitrogen and thereby influenced growth and development, physiological, morphological and anatomical responces. These responces were discussed at crop leaf mass, LA, dry matter allocation, leaf photosynthesis and its related processes, nitrogen fixation and grain yield levels. Lack of responces to density and intercropping indicated the absence of competiveness to growth resources. Height, LA, and biomass changes were via water relations, elongation of meristematic cells and photosynthetic allocation respectively but variations in LA, SLW, LAR, shoot - root ratio and nitrogen fixation were mainly due to the influences of light via leaf numbers, height, photosynthesis and assimilation allocation. This study has demonstrated that competition for environmental resources among sorghum and soybean, due density, and intercropping, influences growth, development, physiological, anatomical, yield attributes, as well as nitrogers-fixation if measured and modelled and rainfall patterns monitored, can give a better understanding of the physiological basis for the observed patterns of growth, development and yield.