Under normal circumstances, the use of herbicides to produce phytotoxicity is caused by misuse or misuse, contamination of the application equipment, volatilization and drift of droplets, effects of soil residues on later crops, improper mixing, and degradation of herbicides to produce toxic substances. Unusually bad environment and so on.
For example, the most commonly used sulfonylurea herbicides have higher activity on weeds and can be used to control weeds in farmland, woodland and non-cultivated land. However, such herbicides are long-term residual herbicides, and the residual time in the soil is long after use, and even if there is a trace residue, it is easy to cause damage to the susceptible crops.
Sulfonylurea long residual herbicides such as chlorsulfuron, metsulfuron, ethametsulfuron, chlorsulfuron, monosulfuron and the like. The method for reducing the amount of the long-remaining herbicide is to use an auxiliary agent, and add 1% of the vegetable oil type auxiliary agent or a nonionic surface active (0.1 to 0.25)% to the diluent. Alternatively, rationally mix different types of herbicides to reduce the amount of sulfonylurea herbicide used.
There is also a combination of appropriate farming measures, ecological regulation and elimination combined with grass control technology system. The prevention of resistance should use the reasonable rotation of different target herbicides; at the same time, take into account the planting methods of water and drought rotation.
It is worth noting that most of the herbicide phytotoxicity is caused by improper human manipulation.
- Improper use period, excessive application or high concentration. When the temperature is high, the concentration of the drug should be appropriately reduced within the recommended range of the label. When the temperature is low, the concentration should be appropriately increased. When the humidity is high, the dosage should be appropriately increased. When the humidity is small, the dosage should be appropriately reduced.
- When it is dry, it is necessary to irrigate the soil to moisten the soil and let the weed seeds germinate to kill. Secondly, it is necessary to master the various herbicides that are suitable for use on any crop to achieve good grass killing effect. The weeding effect of weeds was poor, and the weeding effect was the best in weed seed germination and seedling stage.
- Misuse of herbicides. The combination of herbicides is very common, which can expand the herbicidal spectrum, improve the herbicidal effect, prolong the efficacy period, reduce the stress on the crops, reduce the residual activity, delay the development of herbicide resistance, etc., but often also due to improper mixing. And caused a large area of ​​phytotoxicity. It is necessary to choose medication according to different weeds.
- There are many herbicides, chemical herbicides and biological herbicides; water, powder, emulsifiable concentrate, granules, etc. in the dosage form; selective herbicides and herbicides in the herbicidal mechanism, each herbicide The nature is different. Therefore, we must first understand the nature of various herbicides and carefully mix the herbicides.
- The application of the device has caused dripping and leakage, which resulted in poor weeding effect at the place where the spray was sprayed.
- The nozzles are not properly selected, the droplets drift heavily, and the herbicide sprays should use fan-shaped nozzles. It is best to use anti-drift nozzles when considering wind factors.
- The application equipment is not classified and managed. For example, after the herbicide has been used, it cannot be cleaned thoroughly, and the phytotoxicity occurs when the medicine is applied again.
Environmental factors and meteorological factors are also the causes of phytotoxicity
For example, soil organic matter content, moisture, temperature changes, light intensity, etc. The sulfonylurea herbicide is also taken as an example. It is easily degraded under the acidic condition of pH≤7, and the degradation is slow in alkaline soil with pH≥7, which is easy to affect the post-crop crop; generally the temperature is high and the humidity is high. Conducive to the hydrolysis of sulfonylurea herbicides; on the contrary, the decomposition of the agent is slow and the residual period in the soil is prolonged. The soil organic matter content has little effect on it, and the residual activity in the soil with high organic matter content is generally lower than that of the soil with low organic matter content.
In addition, when using any herbicide, you should consider the problem of controlling the drift of the agent, and try to avoid the occurrence of phytotoxicity caused by drift.
The following methods can prevent drift problems
- Use nozzles specifically designed to reduce drift
- Use a low pressure nozzle or a nozzle with a large spray port
- When the spray effect is not ideal, add anti-drift additives
- Spray as close to the ground as possible
- Apply in the morning or evening of the windy, or when the wind speed is low (less than 9 km / h)
- If the field is critically sensitive to crops, spraying is not recommended in the critical section. Isolation or isolation should be provided.
Herbicide remedy
- For the phytotoxicity caused by photosynthesis inhibitors, timely application of quick-acting fertilizers such as urea and quick-acting fertilizers can be taken in time.
- The phytotoxicity caused by amide herbicides such as alachlor and acetochlor can be sprayed with gibberellin. Other plant growth regulators can be used as antidote to some herbicides
- The application of organic fertilizers, such as human and animal manure, spraying foliar fertilizer or spreading activated carbon, and tilling can eliminate or reduce the activity of herbicides in the soil.
- Continuous spraying of water to wash the seedlings, repeated irrigation and washing the fields to dilute the detoxification can effectively reduce the effects of the phytotoxicity.
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