During the winter months, vegetables in greenhouses are often attacked by cold currents. If management does not keep up, it will cause freezing damage to vegetables in greenhouses. Those who suffer from heavy freeze will not die if they do not save. The prevention and remedial measures for freezing damage to greenhouse vegetables are described below:
First, the greenhouse vegetable freeze injury prevention
1. Increase the cover. In the nighttime, weave grass weirs around the greenhouse, the temperature can be increased by 1 °C ~ 2 °C, and then covered with a layer of film on the grass weir, not only can block the cold wind, but also prevent the rain and snow wet grass weeds, thereby reducing the evaporation of water Heat loss caused.
2. Smoke around the greenhouse. Before the arrival of the cold weather, smoking smoke around the greenhouse can prevent the heat around the greenhouse from radiating to high altitude and reduce the loss of heat.
3. Regularly clean the film. Remove the dust and dirt from the shed film so as to increase the light and increase the temperature of the shed.
4. Cover the film and small shed. High ridge cultivation in the greenhouse, covered with a layer of mulch on the high ridge, can be increased by 2 °C ~ 3 °C; flat hoe cultivation, can take a small shed to increase the temperature.
5. Set up a cold ditch. Trenches are filled in the south side of the greenhouse to fill in straw, straw and other insulation materials to prevent the ground temperature from being dissipated.
6. Double film cover. Under the drip-free membrane, a thin film is placed over the wire of the sling. Because there is air in the middle, the temperature in the shed can be significantly increased.
7. Use a water storage tank to store heat. In the middle of the greenhouse, a storage tank is dug. The bottom of the pool is to be covered with plastic film. The pool is filled with water. The upper part of the pool is covered with a transparent film. When the pool water evaporates, the air humidity increases. The specific heat of water is larger, and the heat absorbed by high temperature at noon can be released at night.
8. Reveal timely grasshoppers. When temperature conditions permit, cover the cover as early as possible. It is usually when the morning sunlight floods the slope of the entire shed. When the grass is open, the temperature in the shed is generally not lower than 18°C. On cloudy days, the light is weak, and we must expel the grasshoppers in a timely manner so that the scattered light can enter. This will allow the temperature to rise and prevent the uncovered grasshoppers from growing for a long time, so that the shed will be cold and the temperature will drop.
9. Spray antifreeze. Before cooling, anti-freeze is sprayed on the leaves, flowers and buds of vegetables to spray the whole plant at the seedling stage to play a role in freezing and freezing.
In addition, it should be noted that it is not possible to use the firewood to raise the temperature in the shed, because the smoke emitted from the firewood is extremely harmful to the vegetables.
Second, greenhouse vegetable damage remedies
1. Reasonably top-dressing. The fast-appropriate fertilizer is applied to the frozen plants to rapidly absorb the plants, increase their cell fluid concentration, enhance the cold-resistant and anti-freezing ability of plants, and promote the recovery of growth. The foliar spraying is more effective than the soil topdressing and the fertilizer efficiency is fast. It is necessary to conduct reasonable spraying according to the characteristics of different vegetables requiring fertilizer. For melons and solanaceous vegetables, the three elements of nitrogen, phosphorus, and potassium are relatively balanced throughout life, and it is advisable to use three-element compound fertilizer and spray-applying. Leaf vegetables have the most demand for nitrogen fertilizers, and should be sprayed with 1% to 2% urea solution. It would be better to add appropriate amount of gibberellin. Rhizome vegetables require more potassium, phosphorus and other elements and can be sprayed with 0.3% potassium dihydrogen phosphate or 1% potassium sulfate solution. The foliar fertilizer should be sprayed evenly and thoroughly, so that the leaf surface is stained with fertilizer solution. 7 to 10 days after spraying, spraying again.
2. Watering in time. Immediately after the occurrence of cold injury, watering is needed to increase the heat capacity of the soil, increase the air humidity in the shed, stabilize the temperature of the shed, suppress the decrease in the ground temperature, stabilize the air humidity in the surface and the shed, and suppress the evaporation of moisture from the frozen tissue. Effectively reduce and control the development of frost damage. The temperature of well water is higher than that of surface water. Groundwater should be used for watering and surface water should not be used. The amount of water to reach the plough layer is appropriate, avoid flood irrigation.
3. Scientific ventilation. After the vegetables in the shed have suffered freezing damage, they cannot be immediately heated in the closed shed. If the temperature rises too fast, the frozen tissue will dehydrate and die. After the sun comes out, the ventilation openings should be opened appropriately. After a while, the ventilation openings should be gradually reduced or even closed. Let the greenhouse temperature rise slowly, so that the frozen tissue can fully absorb water, promote cell rejuvenation, and reduce tissue death.
4. Moderate shade. Frozen vegetables in greenhouses are fragile. It is best not to receive direct exposure to sunlight. A shady shed can be built in the greenhouse to solve this problem. It is also possible to prevent the weather by uncovering a piece of grass through a piece of grass or keeping the insulation warm. The effect of excessive sunny sunlight on the plants revealed that the wilting of the plants was to promptly put down insulation or grasshoppers.
5. Control disease. For partially irrecoverable lyophilized leaves, they must be cut in time to avoid the mildew-induced disease. When pests and diseases occur at low temperature, they shall be sprayed and controlled in time.
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