In recent years, the winter wheat seedlings have died almost every year. Because the wheat population is highly regulated, the rate of dead seedlings below 10% has little effect, but higher than 20% will cause a reduction in production. The reasons for the analysis are as follows: 1. Low temperature freezing damage . Low temperature causes the main reason for wheat dead in winter. The weather is hot and cold, and the temperature changes rapidly, frequently and frequently. Causes the wheat seedling to freeze too fast and thaw too fast. In this alternating freeze-thaw change, the wheat seedlings are too late to adapt and cause physiological function to decline, leading to the death of the wheat seedlings. Any winter wheat that has undergone cold-resistance before wintering can generally tolerate a low temperature of -23°C, and the temperature is low and dead seedlings are serious. Without winter wheat that has undergone cold-resistant exercise, its ability to resist low temperatures has been significantly reduced. In cold winter weather, the permafrost layer is thick, the soil moisture freezes, the root system cannot absorb water from the soil, or the water absorption capacity is very weak. The wheat stems and leaves still transpire and lose water, causing the wheat to gradually dehydrate and die. 2. Soil drought. Annual total precipitation, summer precipitation, and winter precipitation have a significant impact on dead seedlings. Soil moisture is insufficient, and plants do not receive sufficient water supply during the winter wheat season. In particular, in the years when the weather is variable, windy and cold, wheat seedlings die due to drought and water shortage. In the wheat fields where straw is returned to the fields, the soil is loose and cold air is easy to enter, which is more likely to cause frost damage in wheat. 3. Weak seedlings are overwintering. Due to late planting, poor fertility, excessive density, or weak grazing due to grazing. Individual growth of wheat seedlings is weak, and there is little growth before winter, and less accumulated organic nutrients can not meet the needs of winter wheat. In case of winter cold, dead seedlings can be caused in winter, and weak winter varieties with poor frost resistance are more serious. 4. Winter irrigation late. Over pouring winter water is too late. First, wheat has a high water content in the body. In case of cold, it is easy to cause icing and dead seedlings in plants. Second, the frozen ground layer cracks, the root system is broken, cold air enters the lower part of the soil and dead seedlings; Third, the lower layer of the soil is icing, water can not infiltrate after watering, surface ice, over time, the soil is lack of oxygen, and wheat suffocates. 5. Choose inappropriate varieties or soil preparation, sowing too shallow.
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