Zouping County is a major county for corn production. It has planted 43,000 hectares of corn a year, and the rate of corn chemical weeding technology is more than 95%. Practice has proved that this technology is a low-input, high-efficiency weed control technology. Due to the dry weather early in the past few years, the high stubble of wheat and the improper application of technology by farmers, a large area of ​​chemical weeding has not been effective and the drug The phenomenon of harm, in this regard, the author through a large number of observations and experimental investigations were summarized.
First, application issues
1. Improper selection of species
Different herbicide species have different effects on weed control. Some farmers do not understand chemical herbicides, and listen to some arbitrariness. They believe that as long as they are herbicides, weeding can occur. As a result, the phenomenon of seedling death in the corn field occurs from time to time. Most herbicides currently applied in corn fields use plants to selectively weed herbicides for their differences in conduction. If the types of weeds in the field are different, the use of the same agent will prevent and control the effect. Of course, the farmers will hate the grass and blindly increase the dose, resulting in corn injury. For example, 50% acetochlor EC is a herbicide with a wide range of applications. It is also safe for corn and it works well for weeds such as crabgrass and barnyardgrass before the weeds are unearthed. The control effect of weeds such as ramie is very poor.
2. Improper use period
(1) Poor efficacy. Different weeds have different sensitivity to herbicides at different growth stages. Most grassy weeds and broad-leaved weeds generally appear to be sensitive to herbicides at the budding stage. Combining corn safety, most of the chemical herbicides in corn fields are soils. The agent, after weeding in maize, before weeding, unemerged till before the three-leaf stage of corn and before the two-leaf stage of weeds, has ideal control effect on weeds, and is safe for corn seedlings, and is also a soil treatment agent if used. After the five-leaf stage of corn and the four-leaf stage of weeds, corn not only has poor control of weeds, but corn will suffer phytotoxicity. For example, 40% acetylcholine SC (Acetochlor in Atazin) is a popular corn herbicide in the past few years. If used according to technical rules, it has a broad spectrum of herbicides and good efficacy, but some farmers do not see weeds. Medicine, when the grass is used again, the effect is still not good.
(2) Serious injury caused by drugs. The same herbicides, especially soil treatment agents, are generally required to be used before corn seedlings. The smaller the seedling age of corn, the stronger the resistance to herbicides, such as 40% isopropylate SE, which is the safest corn in the current market. Herbicides are used for soil treatment from corn seedlings to post-emergence three-leaf stage. They not only have good corn safety, but also have strong corn seedlings and dark and thick leaves. However, if they are used after the 5 to 7 leaf stage of corn, they often lead to Macular leaf yellow to dry, inhibit growth.
(3) Caused many corn herbicides to remain in the after-harvest, with a long residual period, such as 38% atrazine SC. The residual period in the soil was as long as 3 months. If the medication is too late and the dose is too large, it will have a direct impact. After the crop (wheat, etc.) crop.
3. Improper use of medication
Herbicide application methods are more complex, strict technical requirements, slight negligence, not only affect the weeding effect, but also often cause crop phytotoxicity, such as some farmers will be 20% paraquat AS (grams without trace), 41% Agricultural Daruss AS (grass Lin et al) used herbicides such as herbicides to protect corn, grass, and seedlings from dying at the same time in the corn field. Some used the soil treatment agent as a stem and leaf treatment. Corn injury was often serious, but weeds were basically absent. effect. On the other hand, when the stem and leaf treatment agent was used for soil treatment, it had no effect.
4. Inappropriate dosage
(1) Do not understand the normal amount of each herbicide corn field has its correct amount under certain conditions, mainly through the test and application, such as 40% isopropyl straw SE, in the light loam non-corn field In the case of early days, 180 to 220 ml per mu, the ideal weeding effect, less than 180 ml, often very poor, and higher than 250 ml, there are often phytotoxicity. In the corn field where wheat is currently high, the use of herbicides after wheat harvesting should generally increase the herbicide dosage by 10% to 20%.
(2) Different soil dosages should be different Sand lands have poor adsorptive capacity for herbicides, and are easily leached with water. Clay soils have strong adsorption capacity to herbicides. The amount of soil treatment agent should be increased in the order of sand, loam and clay. Soil organic matter can adsorb and decompose herbicides. The amount of herbicides should be appropriately increased in plots with high organic matter content.
5. Uneven spraying, insufficient water
Spraying of any pesticide requires good atomization. Even and thoughtful, in order to have good efficacy. Using soil treatment agents for chemical weeding in corn fields, only the fine droplets, sufficient water, and even spraying can form a film on the surface of the soil, which has the effect of suppressing the emergence of weed sprouts. Uneven spraying, there is no effect when the weeds sprout out of the film. With insufficient water, most of the liquid falls on the wheat bran and does not achieve the desired effect.
6. Dripping droplets are severe
Due to the current land-based business, small plots and different crops are typically small and full-grained planting patterns. In the spraying process, careless operation often results in sensitive crops such as cotton, melon and vegetables in adjacent plots. Phytotoxicity. In particular, the use of a mobile mist sprayer to spray corn herbicides has caused more serious drift. In the event of windy weather, it often causes severe damage to sensitive crops.
7. Cause changes in weed species in corn fields
Most of the herbicides in corn fields are selective. At the same time, the degree of resistance of various weeds to a certain herbicide is different. If we use a herbicide for a long time, some weeds will be controlled, while others will become dominant species. Therefore, the variety of weeds in the corn field has changed, thus increasing the difficulty of chemical weeding.
Second, countermeasures
1. Strengthen the training and guidance of chemical weeding technology
The agricultural sector should increase the training and guidance of pesticide operators and users so that they can learn more about chemical weeding and avoid various risks that they may incur.
2. Correct use of chemical herbicides
Chemical herbicides are divided into herbicides and selective herbicides. Selective herbicides also differ in soil treatment agents and stem and leaf treatment agents, and are classified into contact type and transmissive type. Herbicides with different ingredients and different varieties have different herbicidal spectrum, adaptability and sensitivity to crops. Before use, we should fully understand the performance of various herbicides, and master their applicable dose, application period, and appropriate methods. , precautions, etc., based on soil quality, climate, corn growth period and type of weeds, grass size and other factors correctly selected herbicides.
3. Have a good grasp of medication
The soil treatment agent should be applied to the soil before the corn seedling and before the 3-leaf period of the weeds before the 2-leaf stage. The three-leaf stage should fully utilize the strong herbicide tolerance and the weed grass sprouts are most sensitive to the herbicide. medicine. The stem and leaf treatment agent is required to apply protective spray after corn 5 leaf stage, try to avoid corn plants in order to achieve the best results.
4. Choose the right dose
The first is to establish the amount of the species in a certain period of growth of the local corn according to the instructions of the agricultural technicians and the pesticide instructions. Second, when soil treatment agents are used, sandy soils should be used with lower dosages than clay soils. When the organic matter content is more than 3%, they should be appropriately increased.
5. Master medication methods
Weeding in the corn field can be done by using soil treatment agents to spray the ground before seedlings are sown. After the 5th leaf stage of corn, the stem and leaf treatment agent must be directly sprayed on the weed stems and leaves, and attention must be paid to the use of inter-row directional spray technology to place a protective cover at the sprayer nozzle to reduce the number of spray nozzles along the ridge and spray on the grass. Splash on corn plants. Spray corn herbicides with enough water, generally 40-50 kilograms per mu, spraying must be safe and thoughtful, not heavy spray, no leakage spray, do not arbitrarily increase the dose, with manual sprayers such as workers and peasants-16 type spray, generally not Promote the use of motorized sprayers.
6. Pay attention to the weather conditions
Most chemical herbicides in corn fields are soil treatment agents, which should be selected after rainy days or after watering, that is, when the soil is wet, spraying, which is conducive to the formation of drug film and improve the control effect. In order to avoid phytotoxicity of crops other than corn fields, wind-free weather should be used and the nozzles should be pressed down to prevent the fog from drifting long distances.
In short, chemical weeding in corn fields has been popularized, but there are many technical problems. In order to make the technology continuously improve and lasting, it is necessary to improve the techniques of pesticide use by farmers as soon as possible in order to achieve the desired results.
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