YIELD AND YIELD COMPONENTS RESPONSE OF CORN/SOYBEAN INTERCROP TO SIMULTANEOUS COMPETITION OF REDROOT PIGWEED AND JIMSON WEED

In order to investigate the role of intercropping of corn/soybean on the resource use efficiency and suppression of weeds, a field experiment was carried out at the Faculty of Agriculture Research Farm, University of Tehran in 2006. Treatments were arranged in a factorial experiment based on a randomized complete block design with three replications. Treatments were five different mixing ratios of corn (Zea mays) and soybean (Glycine max ) consisting of 100% : 0% (P1), 75% : 25% (P2), 50% : 50% (P3), 25% : 75% (P4) and 0% : 100% (P5) . The weed infestation consisted of one weed free (W1), and three levels of weed infestation of redroot pigweed (Amaranthus retroflexus) (W2), jimson weed (Datura stramonium) (W3) and a simultaneous presence of redroot pigweed and jimson weed (W4). Weed density for both species was 15 plant m -1 of crop row in weed infested treatments. The