[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.%[目的] 明确40%氰氟草酯·二氯喹啉酸WP防除直播水稻田禾本科杂草的效果和使用剂量,为大面积推广应用提供科学依据.[方法] 以浙辐203为供试水稻品种,施药试验设8个处理,4次重复,采用随机区组设计,在直播水稻3叶1心期施药,施药时稗草处于2.5～3.5叶期、千金子处于1.5～2.0叶期.[结果] 40%氰氟草酯·二氯喹啉酸WP在直播水稻3叶1心期施药,可有效地防除稗草和千金子等禾本科杂草,用药量900～1 800 g/hm2,施药后45 d对禾本科杂草总草株防效、鲜重防效分别达93.64%～94.86%和93.89%～95.12%,显著高于对照药剂10%氰氟草酯EC 750 ml/hm2、50%二氯喹啉酸WP 450 g/hm2及人工除草处理. [结论] 40%氰氟草酯·二氯喹啉酸WP在直播水稻3叶1心期施药防除效果显著,其经济有效用量为900 g/hm2.
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