The concept of weeding needs to change First, control weed damage rather than eliminate it. There are nearly a thousand kinds of weed species in the country, and there are 20 to 30 kinds of main types that cause damage to crops. According to research, there are more than 50,000 weed seeds per square meter in 30 cm of ploughing. Due to the biological characteristics of weeds, depth and dormancy, weed seeds are germinated out every year, mature seeds are returned to the soil, and the total number is always maintained. The state of little change, no matter how much the people pay for the weeds, the weeds can't be eliminated. Some weeds can even be associated with crops, such as interplanting turf between wheat and small crown flowers in corn fields, which can increase soil fertility, supply crop nutrients, and promote growth. This is to change the concept, not to eliminate and kill the weeds, but to adopt comprehensive measures such as agronomy, chemistry, machinery and other measures to control the hazards. Since herbicides have been used , some people believe that herbicides are omnipotent, neglecting the selection and application techniques of herbicides, not paying attention to the selection of suitable plant protection machinery and carrying out standardized operations, not paying attention to the scientific application of agronomic measures, leading to refractory weed species. Increased, the drug is serious. Secondly, improve the evaluation method of herbicide efficacy. Evaluate the efficacy of herbicides and replace the quantitative method with the reduction rate of weed fresh weight. Tests have confirmed that reducing weed fresh weight by more than 80% can effectively control weed damage, especially perennial weeds, inhibiting growth (rather than eliminating) does not affect crop growth and yield and economic benefits. It is the best condition to control the weed damage within the allowable threshold of economic, ecological and social effects by using various agronomic, herbicide, and mechanical measures. At present, most of the serious use of herbicides is to eliminate a certain weed, and repeated application of herbicides in excess, reducing yield by 40% to 60%, and even production. Invasive weeds may cause harm in a short period of time. As time goes by, crops and weeds adapt to each other, which will inhibit the specific reproduction of these alien species, transform them into common weeds, and gradually reduce the harm. How to choose a herbicide First, the herbicide and its application method are selected according to the efficacy and safety. From the competition of weeds and crops for nutrition, affecting growth and development and yield, herbicides have better effects than early use. It is best to control weeds before they occur and before they occur. The pre-emergence application of herbicides increased the efficacy by 10%-20% compared with the post-emergence application, and increased the yield by 10%-30%. The application of herbicides in the northern autumn was the best for the safety and efficacy of crops, and the yield increased by the pre-emergence application in spring. % to 8%, improve the efficacy of 5% to 10%. Soybeans, corn, potatoes, rice, sugar beets, peanuts, pumpkins, vegetables, cotton, orchards should be mainly pre-emergence herbicides, accounting for more than 85% (including more than 20% in autumn and 50% in spring). 60%), post-emergence application accounted for less than 15%. The rice transplanting field is mainly closed by soil, supplemented by post-emergence stem and leaf spray, and the northern transplanting field is promoted and applied in stages. 100 to 7 days before transplanting is 100%, and 15 to 20 days after transplanting according to grass conditions. Apply a second time. Secondly, try not to choose long-term residual herbicides. If there is no alternative, it can reduce the dosage or mix of multiple agents. The main long-term residual herbicides are atrazine, metsulfuron, chlorsulfuron (chlorsulfuron), imazamox, imidazolidinic acid, flufenazone, chlorsulfuron, oxazinone, clomazone , oxasulfuron, nicosulfuron, simazine, ethametsulfuron, chlorsulfuron, flusulfuron, flufensulfuron, flufenacet, flusulfuron, chlorsulfuron Long, ether benzosulfuron, imazaquin, mesoxalam, clopyral acid and the like. Herbicides should also pay attention to drifting phytotoxicity. Drifting can reduce weeding effects, pollute the environment, and harm sensitive crops. Herbicide that is easy to drift and volatilize, such as 2,4 ~ butyl butyl ester, chlorpyrifos, trifluralin, zhongdingling, and dysentery. Finally, the herbicide structure is adjusted for refractory weeds. For example, the rice transplanting field controls the weedy weeds, and the pyrazosulfuron-methyl or pyrazocillin-ephedrine effervescent tablets are used before transplanting, and the herbicides, pyrazosulfuron-methyl and pyrimidin are used after transplanting. Bismuth, or oxazolone, or oxazinone + pyrazosulfuron. Another example is cornfield control of leeks, thorns, comfrey, pre-emergence of flufensulfuron, thifensulfuron, or sulffenapyr + thiophenesulfuron + atrazine, or pyrisulfuron Amine + 2, 4 drops of isooctyl ester + atrazine mixed. After the seedling, nicosulfuron + bentazone, or sulfamesulfuron + thifensulfuron, or bentazone + atrazine. Pay attention to the prevention of phytotoxicity Agronomic measures to prevent phytotoxicity are important, and timely planting is most important. The traditional sowing period is to calculate the growth period and sowing date based on the average temperature and stable temperature through 10 °C without applying fertilizer or pesticide . After years of research and practice, the daily average temperature is selected to be stable through 13 °C as a new standard for calculating the growth period and sowing date. In addition, the soil preparation should be flat and the seeding depth must be consistent. If the seeding is too deep, the seedlings should consume nutrients, resulting in weak seedlings and phytotoxicity; formulate safe use of pesticides and economic crop zoning, restrict the use of certain drifting herbicides in economic crop planting areas; and herbicides that are susceptible to drifting phytotoxicity For example, 2,4 ~ butyl butyl ester, replaced with 2,4 ~ drops of isooctyl ester, improve the dosage form of the dysentery, effectively solve the problem of volatile migration and phytotoxicity. Adhere to traditional agronomic measures The first is reasonable rotation and close planting. Simultaneous evolution of crops and weeds, all kinds of crops have associated weeds and crop ecotypes. By changing crops and replacing herbicides, we can effectively control the associated weeds of crops and avoid weeds. Close planting helps to inhibit certain refractory weeds. The second is rational farming. The main problem of current agricultural cultivation is shallow ploughing, soil compaction, root stagnation, soil impervious to water, airtight, neither drought nor stagnation, and increased phytotoxicity. It is imperative to break the bottom of the plow and adopt the mechanical deep-deep, deep and shallow tillage measures. After 2 to 3 years, the soil will be turned deep to improve the physical and chemical properties of the soil, and the roots and stems of the perennial grassland will be chopped. The third is to give full play to the mechanical role. The fourth is to plant in the early spring and in stages. According to the different characteristics of weed emergence period, weaving weeds induced by mechanical early spring planting, weeding by staged sowing and staging, and increasing the ground temperature by preserving, promoting the early emergence of crop seeds, which is conducive to the cultivation of strong seedlings. The fifth is cultivating soil. Since the herbicide has been widely applied, some wrong practices such as using herbicides are not suitable for earthmoving, fearing that cultivating destroys the film and affecting the weeding effect; or that it can be ploughed less and save costs, and the result is a weed after a rain. I have to use the herbicide again. In fact, no matter whether the pre-emergence or post-emergence herbicides are applied, the cultivating should be timely and the cultivating is beneficial to control the weeds. The early cultivating is beneficial to increase the ground temperature and promote the growth of the seedlings. Later, the deep cultivating soil is beneficial to control diseases, drought and flood control and fall prevention. . In the general arching period of crops, shallow ploughing of deep loose soil is carried out, and 2 to 3 times of cultivating are carried out after the seedlings. The last time is to cultivate the soil and seal the ridge. 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Spraying herbicides and removing grass is not the best policy