作物和杂草都属于高等植物,除草剂必须具有特殊的选择性才能杀死杂草而对作物无害,否则就会草苗齐死。有些除草剂本身具备选择性,有些虽然缺乏选择性,但通过适当的使用方式,也能达到除草的目的。除草剂的选择性可分为以下几种。 Crops and weeds are all higher plants. Herbicides must have special selectivity to kill weeds while they are not harmful to the crop, otherwise the plants will die altogether. Some herbicides have their own selectivity, some of them although lack of selectivity, but through the proper use of ways, but also to achieve the purpose of weeding. The selectivity of herbicides can be divided into the following categories.