Evaluation the effect of herbicides on weed management and grain yield of rice genotypes in direct- seeded conditions

In order to evaluate the effect of herbicides on weed management and grain yield of rice genotypes, an experiment was conducted at Rice Research Institute of Iran in Rasht during 2016-17 cropping season. The experiment was laid out in a split plot based on randomized complete block design with three replications. The treatments included five levels of weed management as 1- sequential application of pendimethalin followed by bensulfuron-methyl followed by cyhalofop- butyl; 2- pretilachlor fb bensulfuron- methyl fb cyhalofop-butyl; 3- pendimathelin fb bensulfuron- methyl fb propanilﺗ 4- pretilachlor fb bensulfuron- methyl fb propanil) and 5- weedy check under natural weed flora as the main plots and ten rice genotypes as subplots. The results showed that the effects of genotype, weed management and their interaction was significant on all traits including weed biomass, plant height, yield components and grain yield of rice. Rice genotypes showed different responses in terms of evaluated traits at each level of weed management, which may be related to different competitive ability of genotypes. All herbicide treatments significantly reduced the weed biomass and increased grain yield of all genotypes compared with weedy checkﺗ however sequential application of pretilachlor followed by bensulfuron- methyl followed by propanil is the best herbicide combination because of the least weed biomss and highest weed control efficiency and also the highest grain yield in all genotypes. It seems that this combination of herbicides can be a good alternative for hand weeding in order to reduce labor costs and more economical production of rice.