The herbicide that causes phytotoxicity to the lower crops is called long-residue herbicide or long-lasting herbicide. The long-term residue in the soil can last for 2 to 3 years, even up to 4 years, although there is no herbicidal effect, but Sensitive crops can cause phytotoxicity, and severe ones can be produced. Long residual herbicides can be divided into the following two categories: The first type is long-lasting residual time such as imidazolium and chlorsulfuron. It is harmful to the crops of the lower crops. After long-term use of weed community changes, the drug effect is poor, often used excessively, and the crop safety, yield and benefit are low. . At present, China's herbicides are developing rapidly, with complete types and sufficient quantities. They have been oversupplied, and the timing of replacing imidazolium nicotinic acid, chlorsulfuron-methyl and their mixed preparations is ripe. The second type is herbicides such as oxacillin, flufensulfuron, and flufenacetate, which have relatively less harmful species to the squat, and limit the amount of drug used. Mixed use can solve the residual hazard of the sorghum crop. It is effective for refractory weeds after weed community succession, especially for the control of “three dishes†(Duckweed, thorns, big thorns, and leeks) in soybean fields. These herbicides are inseparable. Alternative varieties. In Heilongjiang Province, 480 grams of active ingredient per hectare is safe for sorghum crops; flufenacetate is safe for 250 gram of active ingredient per hectare; oxasulfuron is currently used in small areas. In high pH, ​​low organic matter content, the degradation is rapid and the residual period is short. On the contrary, the residual period is longer. The active ingredient of azoxysulfuron is 38.4~48g/hm2, and the next year can be planted with soybean, corn, wheat , barley, peanut, rice, pea, sorghum, sweet potato, alfalfa, clover, potato and other crops; Tobacco, sunflower; beet, rape, flax, onion, pumpkin, watermelon, eggplant, pepper, radish, cabbage, carrot, cucumber, etc., separated by 26 months. The dosage of azosulfuron is reduced, and the active ingredient is 32g/hm2 or less, which improves the safety of the crop. Roll Forming Machine,Roof Roll Forming Machine,Curved Roof Roll Forming Machine Professional Roll Forming Machine Co., Ltd. , http://www.lnformingmachine.com