Study on the Control Effect of 40% Cyhalofop-butyl/Quinclorac WP on the Grass Weeds in Rice Fields of Direct Seeding Cultivation

[Objective] The purpose was to define the control effect of 40% cyhalofop-butyl·quinclorac WP on the grass weeds in rice fields of direct seeding cultivation and its using dosage so as to provide scientific basis for its popularization and application in large scale.[Method] With Zhefu 203 as tested rice variety, 8 treatments with 4 repeats were arranged and the randomized block design was adopted in the herbicide-applied experiment.the herbicide was applied in the period when the direct-seeding rice was in its 3-leaf and 1-central leaf stage, the barnyard-grass was in its 2.5-3.5-leaf stage and the chinese sprangletop was in its 1.5-2.0-leaf stage.[Result] The grass weeds such as barnyard-grass and chinese sprangletop could be effectively controlled by applying 40% cyhalofop-butyl·quinclorac WP in the 3-leaf and 1-central leaf stage of direct-seeding rice and its using dosage was 900-1 800 g/hm2.After 45 d, its stem control effect and fresh and heavy effect on all the grass weeds reached 93.64%-94.86% and 93.89%-95.12% resp.and they were significantly higher than that of the control herbicides 750 ml/hm2 10% cyhalofop-butyl EC and 450 g/hm2 50% quinclorac WP and than that of manual weeding.[Conclusion] The control effect of applying 40% cyhalofop-butyl·quinclorac WP in the 3-leaf and 1-central leaf stage of direct-seeding rice was significant and its economic and effective dosage was 900 g/hm2.