Response of Canopy Structure of Soybean (Glycine max (L.) Merr.) Cultivars to Weed Competition

Pattern of leaf area and plant dry matter distribution, can play key role in weed-crop competition for achieving the light. A field study was undertaken to aim of investigation of leaf area and dry matter profile of soybean cultivars and weeds. The experimental design was a randomized complete block using a split-plot arrangement with three replications. Main plots were weed infested (natural infestation) and weed free, and subplots were four soybean cultivars (Sahar, Hil, Sari, Telar) and two lines (033, 032). At soybean canopy closure stage, sampling of leaf area and dry matter profile of cultivars and weeds was carried out. Interference with weeds caused different cultivars of soybean shift the maximum layer of leaf area and dry matter to the upper layer of canopy. Distribution of leaf area and dry matter in weeds canopy was related to its species and the growth form. Abutilon theophrasti increased its height and height of branching, and spread its leaves on the soybean canopy. The hill cultivar in weedy plots produced maximum grain yield and had more weed suppressive ability than other ones.