Effect of seed density and molinit rates on barnyardgrass (Echinochloa crus-galli) control in direct-seeded rice in Ahwaz

In order to evaluate the seed density and Molinit rates in direct-seeded rice on barnyard grass control as well as grain yield of rice، LD183 cultivar، a field experiment was conducted in 2005 at Ramin Agricultural and Natural Resources University Mollasani، Ahwaz. The design was split plot in a completed randomized block basis with 4 replications. Main plots were 3 levels of Molinit (3، 5 and 7 lit/ha) with control check and weedy check، and sub plots of 3 seed densities (100، 120 and 140 kg/ha). The increase of herbicide rate to 7 lit/ha، lead to decreasing of dry matter and grain yield، harvest index (HI)، total number of rice tillers and spikes، and the number of grain per spike، plant height and HI of barnyard grass. However، it increased the number of grain per ear، percentage of fertility of rice، dry matter and grain yield of barnyard grass. The increase of seed density (140 kg/ha) lead to decreasing dry matter، grain yield، number of grain per ear and percentage of fertility of rice، compared with 100 and 120 kg seed/ha. However، the number of total tillers of rice، and dry matter and grain yield، number of spike in unit area increased with increasing seed density. The interaction effect of seed density and herbicide rate on dry matter and grain yield، number of total tillers، number of fertile ear in unit area، number of grain per ear and percentage of fertility، and dry matter and grain yield، and number spike in unit area was significantly different. Highest grain yield of rice (6. 71 t/ha) was obtained with 5 lit/ha Molinit herbicide and 120 kg/ha seed density. Highest grain yield of barnyard grass (1. 01 t/ha) was obtained with 3 lit/ha Molinit and 140 kg/ha seed density.