عنوان مقاله [English]
To investigate the effects of sowing date, plant density and weeds on growth indices and yield of soybean (Glycine max L.) a field experiment was carried out during the spring 2009 at University of Zanjan as a factorial split plot on the basis of randomized complete block design, with three replications. Treatments were including factorial of sowing date in two levels (May, 27; and June, 9) and plant density in three levels (low density (25 plants. m-2), optimum density (33 plants. m-2) and high density (50 plants. m-2)) as main plot and weed interference at two levels (control and no control) as sub plot. Leaf area index (LAI), total dry matter (TDM) and crop growth rate (CGR) as growth indices with biological and grain yield of soybean were evaluated. Results indicated that crop canopy was closed earlier with the early sowing and increasing the plant density, that lead to increasing leaf area index and total dry matter. Also the maximum crop growth rate obtained from 50 and 25 plant.m-2 plant density and 27 May sowing date. LAI, TDM and CGR reduced in weed interference. The highest grain and biological yield (1283.04 and 2769.36 kg.ha-1 respectively) were obtained in first sowing date (27 May) and high plant density (50 plant.m-2) in the absence of weeds.