To evaluate of weeds population competition on yield and yield components of Soybean (Glycine max L.) under different agronomic factors, a field experiment was conducted during spring 2009 at University of Zanjan based on a factorial split plot on the basis of randomized complete block design, with three replications. Treatments were including planting dates on May 27th and June 9th and plant density as main plot in three levels: (25, 33 and 50 plants. m-2) and weed control as sub plot at two levels: (control and no control). The results showed that the delayed sowing decreased significantly p]0.01 in most traits such as the number of pods per plant, grain yield and biological yield. Planting on May 27th with 1283.04 kg.ha-1 had the highest grain yield and planting on June 19th with 727.88 kg.ha-1 had the lowest grain yield. Planting density had significant effect on number of pods per plant, grain and biological yield. All studied traits reduced in the response to weed interference.

کلمات کلیدی