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 com/soybean on the resource useefficiency and suppression of weeds, a field experiment was carried out at the facultyof agriculture research farm, university of tehran in 2006. treatments werearranged in a factorial experiment based on a randomized complete block design withthree replications. treatments were five different mixing ratios ofcom (zea mays) andsoybean (glycine max) consisting of 100%: 0% (p,), 75% : 25% (p,), 50% :50% (p3) , 25% : 75% (p,) and 0%: 100% (p,) . the weed infestation consisted ofone weed free (w,), and three levels of weed infestation of redroot pigweed(amaranthus retroflexuss (w,), jimson weed (datura stramonium) (w,) and asimultaneous presence of redroot pigweed and jimson weed (w,). weed density forboth species was 15 plant m of crop row in weed infested treatments. the results showed the highest yield of com (9627.8 kg ha') was obtained in the p,witreatment, and the lowest (3916.7 kg ha') was in p,w4 • but the highest yield ofsoybean (5050,00 kg ha') was seen in p,w i and the lowest (365.67 kg ha') in p,w4•some yield components of com such as the kernel row number per ear , kernelnumber per row, and 1000 kernel weight were highest for p4 wi, but the harvestindex was highest (0.45) for p,wi and lowest (0.20) for p4w4• some yieldcomponents of soybean such as pod number per plant, grain number per pod and 1000grain weight were highest in the monoculture of soybean and the weed free treatment(p, wi). this treatment had the highest soybean harvest index. it could be concludedthat decreasing the com/soybean ratio in the cropping rows will increase the com andsoybean yield components. the highest weed biomass (376.73 g m) was obtained inthe monoculture of soybean infested with jimson weed and redroot pigweed.therefore. it could be stated that com/soybean intercropping significantly reduced theweed biomass comparing to both monocultures.