evaluation of herbicide application and seeding rate on competition between rice (oriza sativa l.) and barnyard-grass (echinochloa crus-galli(

in this experiment which was conducted at a field of ramin agriculture and natural resources university (khouzestan, iran) in 2005, the effect of molinate at 0 (weedy check), 2.16, 3.6 and 5 kg/ha and seeding rate of 100, 120 and 140 kg/ha was evaluated on the competition between rice and barnyard grass (echinochloa crus-galli) in a split plot design with four replication. the interaction effects of herbicide and seeding rates on grain yield, number of inflorescence and number of grain per inflorescence were significant for both crop and weed. in weedy check, the crop grain yield at 120 kg seed/ha was significantly higher than the other seedling rates. in other hand, it was be observed that highest and lowest yield of crop and weed, respectively, was be related to 5 lit herbicide/ha. in this case, there was little difference between different densities. the rice yield in density 120 showed lesser changes in crop yield. in density 120, crop and weed yield relationship have lesser slope in comparison with other densities. ultimately, it seems that optimum crop density can lessen crop sensitivity to other environmental and agronomic factors including weed competition and herbicide use.