Frost prevention

Frost and its preventive measures

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Release time: 2005- 12- 15 news excerpt from wuxuan agricultural information center.

Frost means that the temperature of the ground and plant surface drops to a low enough temperature during the crop growing season, resulting in crop injury or death. When there is frost, there can be frost (white frost) or no frost (black frost). When there is frost, crops may not be frozen. Therefore, it is necessary to prevent frost and not frost.

Frost occurs in weather conditions that may lead to significant cooling. The meteorological conditions for frost formation are sunny and breezy nights. Clear skies at night are conducive to the rapid radiation cooling of the ground or ground objects. On the eve of first frost, it was sunny and cloudless at night. The ground radiation transfers heat to the upper atmosphere, but the atmospheric inverse radiation is weak, giving less heat back to the ground, and the ground temperature drops greatly. So on the eve of first frost, the temperature was low, people felt very cold, and the weather was generally sunny the next day. Therefore, it is said that it is sunny in first frost. "The Book of Qi Yaomin" also says, "It's rainy and sunny, and the north wind is cold, so it will be frosty at night." A scientific exposition of ...

Frost harms crops because low temperature promotes the water between plant cells to form ice crystals, and constantly takes away the water in the cells. The ice crystals gradually expand, which not only consumes the water in the cells, but also causes the protoplasm to dehydrate and deteriorate the protoplasm colloid. Thereby dehydrate cells and cause injury; The metabolic process is destroyed, the protoplasm structure is destroyed, and the ice in the cell is mechanically damaged.

The intensity and duration of frost occurrence are closely related to topography, soil, vegetation, agricultural technical measures and crops themselves. The north slope of the mountain faces the cold wind, with less sunshine and heavy frost; On the south slope, the lee is sunny, and first frost is light. On the east and southeast slopes, the sun shines first in the morning, the temperature of plants changes greatly, and the freezing damage is often heavier. The cold air on the hillside can flow down the slope, and the frost is lighter, while the cold air accumulates in the valleys and depressions below the mountain, and the frost is heavier; Loose soil, with small heat capacity and low thermal conductivity, makes the temperature of the air layer close to the ground drop rapidly, and the frost damage of crops is serious, while the tight and humid soil is the opposite.

Preventive measures for spring frost;

(1) Fumigation method: Smoking in the field on the night of frost can effectively reduce and avoid frost disasters. However, we should pay attention to two points: first, the discharge points should be properly dense, so that the smoke screen can basically cover the whole park; Second, the ignition time should be appropriate, and it should be ignited in the headwind direction from midnight to 2-3 am, and there is still a smoke screen on the ground until sunrise, with the best effect.

(2) Water spraying method: Before the frost occurs, spraying water on the surface of plants with a sprayer can slow down the cooling of plants, increase the water vapor content in the atmosphere, release heat from water vapor condensation, and reduce the frost hazard. In the days of obvious frost, you can spray water many times.

(3) Wetland method: wet soil has large heat capacity, high thermal conductivity and slow surface cooling. Therefore, watering the tea garden ground can reduce the frost intensity before the frost occurs. This method is generally used at the same time as water spraying.

(4) Covering method: Cover the tea shed with straw curtain and film. This method is suitable for small areas. Because of the high cost, white tea should be used, and the first batch of high-grade tea to be picked should be used.

(5) Frost washing method: In case of frost, water or spray water to wash the frost before the sun comes out, which can reduce the frost damage of crops.