温州农区早稻抛秧田的杂草发生特点与化学除草技术研究

Occurrence of weeds in early transplanted rice by seedling broadcasting and their control in Wenzhou,Zhejiang

温州农区早稻抛秧田杂草发生种类以稗草、矮慈菇、节节菜、异型莎草、牛毛毡为主 ,稗草为优势种群 ,杂草危害程度重于插秧田。抛秧后 2d杂草开始陆续出苗 ,抛后 10d呈现出苗高峰 ,比插秧田早 5d ,稗草的出苗高峰出现于抛秧后 5～ 10d。经 3年试验证明 ,禾大壮 +苄嘧磺隆 ,二氯苄和丁苄对禾本科、莎草及阔叶草均有良好防效 ,对水稻安全 ,增产幅度大。不同施药期试验表明 ,二氯苄和丁苄分别于抛秧后 3～ 5d和 5～ 9d使用 ,对水稻株高和分蘖有明显抑制作用 ,故安全有效用药期应为抛秧后 7～ 11d和 11～ 13d。

Field weed investigation showed, Echinochloa crusgalli,Sagittaria pygmaea,Rotala indica Cyperus difformis,Eleocharis yokoscensis are main weed species in early transplanted rice by seedling broadcasting in Wenzhou,Zhejiang.Among them, E.crusgalli is dominant.Weed damage to rice is heavier in seedling broadcasting fields than in dibbling fields.Weeds begin to emerge at 2 d after seedling broadcasting,reach to a peak at 10 d,which is 5 d earlier than in dibbling fields.Field trials in 1997-1999 showed the mixtures of molinate+bensulfuron methy1,quinclorac+bensulfuron methy1,and butachlor+bensulfuron methy1 are highly effective on weeds and safe to rice with increased rice yield.However,plant height and tilling number are strongly prevented if the mixture of quinclorac+bensulfuron methy1y is applied at 5-9 d after seedling broadcasting or butachlor+bensulfuron methy1 applied at 3-5 d,so they are recommended to be sprayed at 11-13 d or 7-11 d after seedling broadcasting,respectively.