Methods for applying herbicides to wheat to prevent freeze-related herbicide injury
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How can freeze-related herbicide injury be prevented when applying herbicides to wheat? What methods can solve itWhen frequent cold waves combine with drought, improper use of herbicides in wheat fields can easily cause freeze-related herbicide injury.
Causes
Reason for herbicide selection In many areas, wheat fields have long used herbicides containing isoproturon, such as high-permeability isoproturon, bensulfuron-methyl-isoproturon, benzylpenicillin-isoproturon, and chlorsulfuron-isoproturon. After applying these herbicides, freeze-related herbicide injury readily occurs when cold waves hit.
Frequent cold waves According to statistics, from November 20, 2008 to January 20, 2009, there were 5 cold waves. Such frequent cold wave weather easily leads to freeze-related herbicide injury in wheat fields where the above herbicides were used.
Large dosage and high herbicide solution concentration Investigations in townships (towns) such as Xiejia, Hanliu, Gaoyou, and Longqiu found that all fields with severe freeze-related herbicide injury had increased herbicide dosage. In some fields, the per-mu dosage of 50% isoproturon was increased to more than 230 grams, and some were mixed with fenoxaprop-P-ethyl. When cold waves are frequent, freeze-related herbicide injury in wheat fields with increased dosage is unavoidable. Another investigation showed that insufficient water added and excessively high herbicide solution concentration were also one of the causes of freeze-related herbicide injury.
Drought The drought in the winter of 2008 was also an important cause of freeze-related herbicide injury. According to investigations, freeze-related herbicide injury was severe in all wheat fields with low soil moisture and dry, white bed surfaces. In the same field, freeze-related herbicide injury was mild in moist places, and the aboveground parts of wheat seedlings did not freeze to death, while in places where the soil was dry and white, the aboveground parts of wheat seedlings all froze to death. This indicates that high field humidity has a cold-resistant and heat-preserving effect on wheat seedlings and can prevent freeze-related herbicide injury.
Extensive tillage In fields with relatively extensive ploughing and preparation and no-till wheat planting, wheat seedlings root shallowly, and the tillering nodes have no soil layer protection, so freeze-related herbicide injury is severe.
Large seedlings and weak seedlings Wheat with a young seedling age has relatively stronger cold resistance, and vice versa it is weaker. Strong seedlings have milder freeze-related herbicide injury, while weak seedlings and diseased seedlings have relatively more severe freeze-related herbicide injury.
Soil factors Freeze-related herbicide injury mostly occurs in sandy soil, and basically does not occur in clay soil.
Preventive measures
First, determine the appropriate application period according to weather forecasts. Today's weather forecasts are already relatively accurate. In particular, the application of satellite cloud images can accurately predict the weather conditions for the following week. As long as attention is paid to the weather forecast, application during adverse weather can be avoided.
Second, strictly control the dosage of isoproturon, do not increase the dosage at will, and use sufficient water.
Third, when applying, ensure suitable soil moisture to prevent freeze-related herbicide injury. Do not apply when the soil is dry, as dry soil also affects the efficacy of isoproturon. If the wheat field is dry, water can first be added to preserve moisture before application.
Remedial measures
For wheat fields where freeze-related herbicide injury has occurred, corresponding remedial measures should be taken according to the specific situation. For fields where the survival rate of tillering nodes is 70%-80%, fertilizer and water management should be strengthened to promote recovery of wheat seedling growth. For fields where the survival rate of tillering nodes is 30%-40%, especially wheat in extensively prepared land and sandy soil, where the tillering nodes are exposed on the soil surface and the wheat seedlings cannot recover growth, changing to other crops may be considered.
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