First, the water spray method: In the forecast frost, water 2 or 3 times in the crop or plastic film at 2 am to 3 am, spray 1 hour. In the early morning, due to the high humidity and humidity between the air and the plants in the field, the latent heat of condensation will be released when the water vapor condenses into dew, and the water temperature is higher than the temperature (the temperature of the water at the time of the first frost is approximately 15°C at 0°C), and the water is cold on the crop. Condensation will release heat, so the use of water spray defense generally does not have frost formation.
Second, the irrigation method: It can be watered in the evening before the expected occurrence of frost. Because of the large heat capacity of water, the thermal conductivity is good. Irrigation can not only increase soil moisture, but also increase the air humidity near the ground floor. It can reduce the degree of radiation of long-wave radiation at night, thus protecting the ground heat and increasing the temperature of the formation by about 2°C. Wet soil has higher heat capacity and thermal conductivity than dry soil. It absorbs sunlight energy during the day and can store more heat, and it is stored in deep soil. It can release heat from the deep layer to the surface of the ground when the surface radiation heats up at night, which can delay The temperature near the surface decreases.
Third, the smoke method: According to the weather forecast, in the low-temperature frost coming soon, in the wind on the use of weeds, dead branches, fallen leaves and other smoke. Before the ground temperature has not been radiated in large quantities, it is ignited and allowed to burn slowly to increase the temperature near the surface gas layer and prevent the cold air from sinking to prevent frost. Smoke smoke can generally increase surface temperature by 2°C~3°C. However, this method can pollute the atmosphere and is only suitable for short-term frost and use in valuable crop fields.
4. Coverage method: Before the onset of the cold wave, cover crops or ground with straw, weeds, straws, mats, or nylon membranes, or bundle the whole plant, so as to prevent cold air from attacking outside and reduce ground heat. Lost on the outside, not only can protect the leaves from frost, but also protect the heart and growing points from frost.
Fifth, fertilization method: 3 to 4 days before the advent of frost, apply fertilizer such as manure, compost, and ash in the field, which can not only increase the temperature and soil fertility, but also make the crop grow vigorously and strengthen the body's ability to resist cold. After the frost is frosted, timely management of fertilizers, watering, loose soil, etc. shall be carried out on the frozen crops, and timely spraying shall be taken to prevent the occurrence of diseases.
6. Wind barrier method: Before the frost comes, set up a windbreak to the north of the crop field to stop the cold wind from invading, so that the crops can be reduced or protected from the hazards of cryogenic frost.
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