Herbicide technique: strict control of crop sensitivity to herbicides. Different crops sensitive to herbicides wholesale cornfield different herbicides, if not according to the sensitivity of the crop to the herbicide selection agent, even using a herbicide for corn field crop safety of herbicides, sometimes prone to drug harm. General herbicide for broadleaf weeds in dicotyledonous crops sensitive to herbicides for controlling weeds in cereal crops sensitive. Herbicide technique: pre-emergent herbicides only through weeds radicle, coleoptile or hypocotyl absorbed herbicide manufacturers cornfield, and kill weeds after emergence of weeds use, generally no herbicidal effect or weeding the effect is very low. Post-emergent herbicide can also use safe and effective in certain growth stages of weeds or crops.