Interference effect of sorghum (Sorghum bicolor L.) on soybean (Glycine max L.) growth and grain yield.

To evaluate the effect of sorghum interference on soybean growth parameters and grain yield, a field study was conducted in experimental field of the Faculty of Agriculture, The University of Tabriz during 2002 and 2003. Treatments were arranged in a factorial experiment using a randomized complete block design with three replications with additive series method. The first factor consisted of soybean densities of 20, 30, 40, and 50 pants/m2 and the second factor included sorghum densities of 0, 4, 8, and 12 plants/m2. Results showed that the highest dry matter accumulation (DMA), crop growth rate (CGR) and grain yield (GY) of soybean were observed in pure stands of soybean. Among pure stands, the highest and the lowest DMA, CGR and GY were achieved in soybean densities of 50 and 20 plants/ m2, respectively. These parameters were decreased by increasing sorghum density. However, the loss rate was higher at 4 plants/m2 as compared to other sorghum densities. Therefore, it can be concluded that DMA, CGR and GY are decreased, due to increasing sorghum density; however, these parameters are slightly affected by soybean density.