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

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。

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

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-broad-casting rields than in dibbling firlds 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-methyl ,quinclorac + bensulfuron-methyl ,and butachlor + bensulfuron-methyl 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-methyly is applied at 5 - 9 d after seedling broadcasting or butachlor + bensulfuron-methyl applied at 3 - 5 d,so they are recommended to be sprayed at 11 - 13 d or 7 - 11 d after seedling broadcasting, respectively.