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(一)棉田草害的发生特点: 春茬直播棉田,由于播种时间较早、行距较大、密度较稀,封行期也较迟,因而杂草具有发生量大、出草持续时间长、种类多、群落复杂等特点。据1980～1985年田间定点观察,从棉花播后10天左右到8月上中旬,田间都有杂草出土,出草数量呈多峰曲线,高峰一般出现在棉花播后20～45天和梅雨期间,出草持续时间达100～120天,平均每平方米出草1402.7株,杂草种类有45种之多。 (二) 目前棉田使用的除草剂评价:
(A) Occurrence characteristics of cotton grass damage: Spring stubble direct broadcast cotton field, due to the earlier sowing time, row spacing larger, more dilute density, sealing line later, so weeds have a large amount of production for a long duration, Many species, complex community and so on. According to the field observations from 1980 to 1985, from about 10 days after cotton sowing to mid-August, the weeds were unearthed in the field and the number of drafts was a multi-peak curve. The peaks generally occurred 20 to 45 days after cotton sowing, During the drafting of the duration of 100 to 120 days, an average of 1402.7 plants per square meter was drafted, as many as 45 species of weeds. (B) the current use of herbicides in cotton evaluation: