有害杂草和害虫的控制？
美国和加拿大已引入的欧洲蓟，它是一种有害的杂草。
European thistle naturalized in United States and Canada where it is a pernicious weed.
据说，这些大豆从美国运输过来，经常包含了有害的杂草或者除草剂残余。
It said soybeans shipped from the US often contained harmful weeds, or herbicide residue.
结果表明，放牧能明显抑制一年生禾本科杂草及播种多年生禾本科牧草的生长，但对白三叶和草地有害植物的生长都有促进作用。
The results showed that grazing restrained the growth of annual gramineae weeds and perennial gramineae grass, but accelerated the growth of white clover and noxious plants.
结果表明，放牧能明显抑制一年生禾本科杂草及播种多年生禾本科牧草的生长，但对白三叶和草地有害植物的生长都有促进作用。
The results showed that grazing restrained the growth of annual gramineae weeds and perennial gramineae grass, but accelerated the growth of white clover and noxious plants.
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