In agriculture now have do without the help of herbicides, but herbicides are chemicals, how to choose, use of herbicides is an important element, the following are some suggestions for experience, for reference:
I. Formulating prevention strategies based on the characteristics of weeds in wheat fields The occurrence of weeds in wheat fields is affected by geographical environment, meteorological factors, and farming systems. In the Huanghuai winter wheat area, there are two peaks of grass before and after winter. In the general year, weeds begin to germinate 5-7 days after wheat sowing, and the first weed peak is formed in 30-45 days. After winter, weeding begins in mid-to-late February and peaks in mid-March. Under normal circumstances, the amount of grass before winter reaches 70-80%, and only 20-30% after winter. In the years when the temperature is high and the rain is too high, the amount of grass before winter is large, and the amount of grass in the dry year is less. The amount of grass weeded after winter is also affected by temperature and humidity. Since the weeds have been basically released before winter in normal years, the wheat plants are short and easy to chemically weed. Therefore, we should adopt the "control strategy of the spring grass Qiuzhi." Chemical weeding can be carried out by means of pre-emergence blocking and weed 3-4 leaf stage stem and leaf treatment.
2. Selection of herbicides according to the type of weeds in the field According to the survey data of the plant protection station in Suining County, Jiangsu Province, there are 17 families of wheat weeds in 15 families. The most harmful to wheat are: looking at Mai Niang, hard grass, bluegrass, wild Oatmeal, ryegrass, pork broth, sorghum, big nest, leeks, sage, sage, buddha, lacquer, rice, thorns and reeds. We can simply divide these weeds into two major categories: grass weeds and broadleaf weeds.
Control grass weeds can choose: green meron, isoproturon, acetochlor, benzoxachlor, methyl disulfuron and so on. Since different weed populations respond differently to the sensitivity of these herbicides, they are further refined in the choice of agents.
For example, in the field of wheat straw and wild oats, you can choose to control the oxazoline. The herbicidal spectrum of acetyl oxalic acid is slightly wider than that of oxazolyl and herbicide. The herbicidal effect is better than that of oxazocilin. Under the effective content of 4-6 grams per acre, it can prevent ryegrass and hard before winter. Grasses and other difficult weeds; chloromeron and isoproturon can effectively control most annual grass weeds and some broad-leaved weeds, especially isoproturon is still the preferred agent for controlling various weeds in wheat fields. .
There are many types of broadleaf weeds in wheat fields, and there are many varieties of herbicides. It should be selected according to specific weed communities.
The herbicides currently registered in wheat field to control broadleaf weeds are: benzosulfuron, thifensulfuron, bensulfuron-methyl, a, chlorsulfuron (due to the slow decomposition of A, chlorsulfuron in the soil of PH>7) The residual phytotoxicity is heavier, and it is banned in the dry farming area north of the Yangtze River. Dimethyltetrachloride, 2.4-D butyl ester, flufenoxyacetic acid, acesulfame, oxadiazon, diflufenacil, etc. Among them, bensulfuron-methyl is still one of the current varieties. In order to expand the herbicidal spectrum and improve the weeding speed and herbicidal effect, the compounding method is often adopted. Such as prevention of piglets, mother-in-law, sown wormwood, leeks, etc., the choice: benzenesulfuron + acesulfame; benzenesulfuron + oxadiazon; chlorofluoroacetic acid + methyl tetrachloride.
Control wild cockroaches, Maijiagong, big nest vegetables, sorghum, etc., choose: flupiroxine + dimethyl tetrachloride; oxadiazon + dimethyl tetrachloride.
Now there is a ternary compounding agent, such as oxadiazon + bensulfuron + dimethicone, which can basically prevent all broadleaf weeds in wheat fields.
Third, according to the herbicidal properties of herbicides, the chemical herbicides have different biological activities and grass-killing methods. Therefore, it is necessary to use the herbicides to obtain the desired control effect.
For example, acetochlor: amide herbicides, mainly based on bud sheath absorption, have control of broad-leaved weeds of annual grass weeds and some small seeds, and have a certain sealing effect. It can be used for soil closure after sowing in wheat. The herbicidal effect is greatly affected by soil moisture. Under drought conditions, it is not conducive to the effect of the drug. The herbicidal effect is poor. When the water is accumulated in the rain field after application, It is easy to produce phytotoxicity.
Isoproturon: Urea herbicide, mainly to control some grass weeds and some broad-leaved weeds (good effect on the complex), can be used before and after bud, but the best effect after early post-emergence. It can be used in the pre-emergence to 4-leaf stage of wheat (barley). The efficacy of isoproturon is also affected by soil moisture. The effect is not good under drought conditions, and the post-emergence use is better than pre-emergence.
Cinozocilin and acetyl oxalic acid are both stem and leaf treatment agents, and there is no blocking effect, so stem and leaf treatment can only be carried out after the weeds are out.
Bensulfuron-methyl: a urea herbicide, mainly based on stem and leaf absorption, has a blocking effect, mainly to control broadleaf weeds, and has the best effect in weeds 3-4 leaf stage. Due to the slow speed of dead grass, in order to expand the spectrum of killing grass and increase the speed of dead grass, it is often used in combination with oxazolone, metformin, 2.4-D and flufenacetate.
Zoxaconin: stem and leaf contact agent, no systemic conductivity, used to control broadleaf weeds, burns on wheat leaves when used in large amounts, dead grass is fast, but weeding is easy to relapse, and it is prone to large, large nests The effect of the dish is poor, and it can be used in combination with bensulfuron-methyl and metformin, and is best used in the weed 3-4 leaf stage.
Glyphosate is a systemic endogenous herbicide. It can be used for systemic application, and it can be applied 5-7 days before wheat grouting. It has good effect on preventing reeds in wheat field and has no effect on wheat grouting.
Fourth, improve the use of technology, play herbicide herbicidal efficacy herbicides have their own characteristics, must improve the use of technology, maximize the herbicidal herbicidal efficacy, in order to achieve good herbicidal effect, and reduce or avoid the occurrence of phytotoxicity. The following relationships should be handled correctly.
1. The relationship between application and climate. When the weather is dry or the wind speed is high, the application will increase the evaporation and drift of the liquid. The amount of liquid attached to the weed surface and the soil surface will decrease, resulting in a decrease in herbicidal effect. The weather conditions in dry and windy conditions should be avoided. Apply underneath.
2. The relationship between application and temperature. Many herbicides have enhanced activity under high temperature conditions, and the activity is lowered under low temperature conditions, and the speed of dead grass is slowed down. Generally, the average daily temperature is greater than 8-10 ° C to benefit the drug. However, some herbicide varieties can still obtain good herbicidal effects when applied at a daily average temperature of about 5 °C.
Such as benzoxazole, acetyl oxalic acid, tribenuron, oxadiazon and the like. Before winter, the average daily temperature is about 5 °C (no ice at night is good), and good weeding effect can still be obtained after winter.
The use of isoproturon should be applied to the cold-tailed warm head, and the application should be stopped 2-3 days before the cold current, otherwise it may cause freezing damage.
3. The relationship between application and humidity. Whether it is soil closure or stem and leaf treatment, it is necessary to have suitable soil moisture. Under drought conditions, it is not conducive to the efficacy of the drug, and should be avoided under too dry conditions.
4. The relationship between application and water consumption. The amount of water used during the application depends on the amount of the drug solution and the uniformity of the application, thus affecting the herbicidal effect. The application of the herbicide requires no heavy spray or no leakage, and the repeated part is easy to cause phytotoxicity, and the weeds in the place where the spray is leaked are not dead. According to practical experience, when the soil is closed and weeded, the amount of liquid used for the acre is 45-60 kg (manual sprayer 3-4 barrels of water), and the stem and leaf treatment agent is 30-45 kg (2-3 barrels of water). .
5. The relationship between application and land preparation quality. The surface of the soil is finely divided and flat, which is conducive to the formation of a drug film by the liquid medicine, and the herbicidal effect is good. The soil surface is not flat, and the soil block is not conducive to the closure of the soil surface, and due to the freezing and thawing effect in winter, the large clods are broken, resulting in increased grass yield in spring and reduced herbicidal effect.
V. Causes and Countermeasures for Recurrence of Weeds In the actual chemical weeding process, there are some areas where the dead grass is not complete and the weeds recur. If the area is small and the amount of weeds is small, it can be considered as a normal phenomenon. Because it is inevitable that there will be leakage and light spray in the weeding process, and some weeds will inevitably appear in the weed community. Chemical weeding has no 100% effect. However, if there is a large-scale recurrence, it should be taken seriously. After many years of observation and summary, the author believes that there are the following reasons for the recurrence of weeds:
1. Herbicide is too fast, only for wheat fields: For example, oxadiazon is a herbicide for stem and leaf contact, and the weeding speed is fast. When the weed is slightly larger, it can only kill most of the leaves above the ground. Grass growth points and roots are not dead, easy to relapse.
2. The concentration of the herbicide used in the herbicide is too high, which also causes the phenomenon of quickly killing the leaves and not dead roots.
3. The amount of medicinal water is too small and the spray is not uniform. According to the actual investigation, under the same herbicide dose, 1 barrel of water (about 15 kg) was sprayed per mu, and the recurrence rate was 20% higher than that of 3 barrels of water per mu.
Countermeasures: 1. Solve the problem of reasonable ratio of quick-acting and slow-acting herbicides. Such as: benzosulfuron + acesulfame compound formula, if the amount of acesulfame is more than 20 ml (10% emulsifiable concentrate), the speed of dead grass is 3-5 days, the absorption and conduction of weedsulfuron by weeds The amount drops and the weeds tend to recur.
Therefore, we can control the dead grass time to 7-10 days, thus reducing the recurrence of weeds. Practice has proved that the formulation of benzosulfuron + acesulfame is 10-15% +10% of benzsulfuron-methyl 8 ml of flufenacetate is preferred.
2, improve the quality of pesticide application, and strive to be uniform and transparent. The quality of the application directly affects the herbicidal effect. It is required to apply the manual sprayer. The amount of the liquid used in the acre is not less than 30 kg. It is necessary to ensure that it is not re-sprayed or leaked.
6. Causes and countermeasures of phytotoxicity With the development of science and technology, the scope and area of ​​herbicides are rapidly expanding. The emergence of herbicide phytotoxicity has become a common phenomenon. In severe cases, not only the loss of crop yields, but also social problems have attracted the attention of governments at all levels.
The causes of herbicide phytotoxicity are multi-faceted, with the nature of the herbicide itself; the problem of adverse climatic conditions; the problem of sensitive period of crop growth; and the problems caused by the irregular application of pesticides by the applicator. These problems sometimes exist alone, sometimes coincidentally, and it is difficult to distinguish between primary and secondary. Due to the length of the article, it will not be detailed.
Basic countermeasures: Scientific research workers should develop herbicides with higher safety and more convenient use; manufacturers should produce qualified herbicide products in strict accordance with the standards; pesticide distribution and agricultural technology promoters should be proficient in herbicide related knowledge. To strengthen technical guidance for farmers; farmers should also actively learn scientific and technological knowledge, improve the knowledge and use of herbicides, in order to avoid or reduce the occurrence of phytotoxicity.
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