Cold spring is one of the agricultural disasters and has a great impact on the production of vegetables in spring. From the difference in weather characteristics, the spring cold is divided into two kinds of disasters: cold damage and late spring frost. The common cold chilling damage is mainly the continuous low temperature appearing in March and April, accompanied by continuous rain and insufficient sunshine. It can produce different degrees of chilling injury to spring vegetable seedlings, fruit and vegetable production in protected areas, and early-ripening vegetable production in open fields, resulting in various losses such as rot roots, dead seedlings, falling flowers and falling fruit, and early convulsions. Late spring frost is also a major disaster for spring vegetable production. Usually occurs in early and late April after the early planting of vegetables, the weather is clear, the daytime temperature has reached 16-17 °C, the night ground suddenly dropped to 0 °C or 0 °C below, so that the growing field of vegetable plants in the field frost, got damage. Therefore, we must be vigilant against cold spring damage and late spring frost, and make prevention work as soon as possible. 1. Strengthen cold-tempered exercise at the seedling stage to improve the cold resistance of seedlings. After the seedlings emerge, the seedbed should be ventilated, and gradually increase ventilation with warmer weather. The seedlings should be subjected to low-temperature exercise to improve the cold resistance of the seedlings and to adapt to outdoor low-temperature environment. 2, increase protection facilities. There are two ways to increase protection facilities: First, build wind barriers. The wind barrier has a blocking effect on the cold air, and there is a microclimate in the wind barrier group. The airflow can prevent the ground from further cooling. Wind barriers should maintain a relatively close distance, usually about 2 times the wind barrier height is appropriate. The second is planting trenches and covering the mulch. When planting vegetables in early spring, the ditching planting method can be adopted, and the ditch depth requires more than the height of the seedlings, and then the dura can be covered with a plastic film. However, it should be noted that the film can not suppress the seedlings. Otherwise, the top of the vegetable seedling will still be frozen. 3, temporary warming. Production in protected areas can be temporarily warmed in the nursery shed or production shed with the help of a simple coal stove to increase the temperature in the shed and prevent freezing damage. However, open fires should not be used to prevent fires. 4, irrigation. When strong cold air passes, the weather is clear, there is no wind or breeze during the night, and the temperature drops rapidly, especially when the local surface temperature falls below 0°C. When the frost occurs, well water can be poured on the ground to increase the ground temperature. This method can increase the ground temperature from 0 °C to 8 °C, to avoid frost. 5, smoke. On a frosty night, smoking in the fields can effectively reduce or avoid frost disasters. But there are two things to note: First, the fireworks should be dense enough to allow the smoke screen to cover the whole park; second, the lighting time should be appropriate. It should be lit in the wind direction, from midnight to 2-3 o'clock, until the sunrise. There is a smoke screen covering the ground. This works best. 6, spray water. Before the frost occurs, spraying the water on the surface of the plant with a sprayer can slow down the body temperature and increase the content of water vapor in the atmosphere. The water vapor condenses and releases heat to mitigate frost damage. 7, cultivator. Cultivating before frost can reduce the degree of frost damage. Because the temperature in the spring rises gradually, after the clay is loosened, the solar thermal energy can be better absorbed and stored. Once the frost comes, the frost can be alleviated because a part of the heat has accumulated in the soil.
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