What precautions should be taken for chemical weed control?
What should be noted in chemical weed control? Please provide an introduction. Chemical herbicides have the characteristics of strong selectivity and strong specificity. Their application technology requirements are more stringent than those for insecticides and fungicides, and improper use often causes phytotoxicity. To give full play to the role of herbicides in agricultural production, the following seven points should be noted during use....
What should be noted in chemical weed control? Please provide an introduction
Chemical herbicides have the characteristics of strong selectivity and strong specificity. Their application technology requirements are more stringent than those for insecticides and fungicides, and improper use often causes phytotoxicity. To give full play to the role of herbicides in agricultural production, the following seven points should be noted during use.
(1) Correctly select the pesticide. First, select the pesticide according to the target of control; whichever weeds predominate in the field, choose the herbicide whose weed-killing spectrum corresponds to them. Second, select the applicable herbicide according to the crop in the field. Third, select the pesticide according to the application period; those for pre-emergence after sowing must not be used post-emergence, and those suitable for soil treatment must not be used for stem and leaf treatment.
(2) Strict dosage. The dosage of herbicides must strictly follow the standards specified in the instructions, and the dosage must not be increased at will. When 2 or more herbicides are mixed for application, the dosage of each herbicide should be 1/3-1/2 of the conventional dosage of that herbicide. For herbicide use on mulched land, the dosage should be 3/4-2/3 of the conventional dosage. Per 667 sq m, the amount of liquid pesticide (after diluting the original liquid with water) is generally about 3 kg for soil treatment, and generally no less than 40 kg for stem and leaf treatment.
(3) Scientific pesticide preparation. First, scientifically mix herbicides; when using 2 or more herbicides at the same time to kill multiple weeds, the mixed herbicides must have different weed-killing spectra, but the applicable crops, applicable periods and methods of use must match. Second, scientifically prepare the liquid pesticide; first dissolve the wettable herbicide in a small amount of water to make a mother liquor, then fill the sprayer halfway with water, pour the mother liquor into the sprayer, and finally add enough water as required, shake well, and spray. If a wettable powder is mixed with an emulsifiable concentrate, first make the wettable powder into a mother liquor, then pour in the emulsifiable concentrate, and add enough water according to the above method before application.
(4) Apply at the appropriate time. Strictly apply according to the period specified in the herbicide instructions. Those suitable for pre-sowing treatment should be used to treat the soil before sowing, and those suitable for post-sowing pre-emergence should be applied after sowing and before emergence. For herbicides used for stem and leaf treatment, on the basis of clearly understanding the crop growth period, it is essential to avoid its sensitive period and apply at the 2-4 leaf stage of the weeds, so as to achieve effective weed control and prevent phytotoxicity.
(5) Choose the right time to spray. Spraying herbicides should as far as possible avoid high temperature, high humidity or windy weather, to prevent phytotoxicity or reduced efficacy. Generally, it is best to choose clear, windless weather at 20°C-30°C. In high-temperature seasons, it is best to do it before 10 a.m. or after 4 p.m.
(6) Scientific operation. When spraying herbicides, operate carefully and scientifically, achieving uniform and appropriate walking speed, stable and moderate sprayer working pressure, accurate field back-and-forth overlapping, no missed spraying and no repeated spraying, and keep the nozzle as low as possible. When useful, spray the downwind side first, then the upwind side; the direction of the nozzle holes should be consistent with the wind direction, and the walking direction should be perpendicular to the wind direction. When there are other sensitive crops around the treated field, leave a certain distance as a buffer zone. During stem and leaf treatment, try to make the liquid pesticide wet the stems and leaves but do not let the liquid pesticide drip onto the ground. In short, application must be uniform and consistent.
(7) Clean the equipment. The sprayer and other equipment used for spraying herbicides must be thoroughly cleaned with alkaline water after use before they can be used in fields of other crops, to prevent phytotoxicity.
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