Sorting selective herbicides by their nature: Some herbicides kill certain weeds, but others are ineffective, safe for some crops, but harmful for others, this is selective, with this A characteristic herbicide is called a selective herbicide. The selectivity of the herbicide is not absolute, but relative, that is, the choice of herbicide does not affect the crop at all, can kill the weeds, but chooses under certain objects, dosages, time, methods and conditions. Sex, selectivity is determined by the selectivity coefficient. The larger the coefficient, the safer it is. A selective herbicide with a selectivity coefficient greater than 2 can be generalized.

Classification of systemic herbicides by action: Some herbicides can be absorbed by weed roots and leaves separately or simultaneously, transported to various parts of the plant through the transporting tissue, destroying its internal structure and physiological balance, resulting in plant residues. Death, this method is called systemic, and herbicides with this characteristic are called systemic herbicides.

Contact herbicides: Some herbicides are sprayed onto plants and can only kill the part of the plant tissue that is in direct contact with the agent, but cannot be internally absorbed. A herbicide with this property is called a contact herbicide. This type of herbicide can only kill the aerial parts of weeds, and has a poor effect on perennial weeds in the lower part of the weeds or underground reproductive organs.

Sort the soil treatment agent according to the application object: spray the herbicide on the surface layer of the soil or mix the herbicide into the soil to a certain depth by mixing operation to establish a herbicide sealing layer to kill the germinated weeds.

Stem and leaf treatment agent: The herbicide is diluted in a certain amount of water or other inert filler to spray the weed seedlings, and the weeds are eliminated by the absorption and conduction of the stems and leaves of the weeds. Stem and leaf treatment mainly uses the physiological and biochemical selectivity of herbicides to achieve the purpose of killing grass and protecting seedlings.

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