After the winter, the temperature continued to drop and the crops entered the wintering period. Although the weather is fine during the day, the temperature has gradually decreased, and the temperature in the greenhouse has also begun to decrease, causing low temperature barriers in the crops. The main symptoms are yellow leaves, drooping tips, etc., so the farmers’ friends can make greenhouse vegetables before the cold current falls. Keep warm to prevent crops from being damaged due to freezing damage!
Recognize the symptoms of chilling
Cold damage generally means that the temperature has not reached the freezing point, and the low temperature causes the physiological abnormality of the vegetables. The symptoms of cold damage are not as obvious as the frost damage, which often makes the growth of vegetables not normal, but good management can still be restored. The main symptoms of cold damage to vegetables are as follows:
1. The leaves are drooping. When the night temperature is below 10 °C, the vegetable plants will show that the leaves are drooping and the leaves are wrinkled. The leaves developed at low temperature are deeply nicked, the leaves are long, the leaves are dark, and the growth is slow.
2. Yellowing. The plants grow slowly, and the color of the leaves generally becomes lighter and yellower. This chilling injury is often caused by persistent low temperature, low light, weak photosynthesis and overall lack of nutrition. Because its symptoms are somewhat similar to nitrogen deficiency, it is often mistaken for lack of fat.
3. Water stain symptoms. When the temperature of the low temperature is long and the humidity in the greenhouse is large and the ventilation is less, the water stains may appear on the back of the leaves, especially cucumbers and peppers. This is due to the low temperature at night, especially when the ground temperature is still high, and the water in the cells flows into the intercellular space. When the plant grows well, the water stain can disappear after the sun comes out. However, if the plant is weak or completely weak, the water temperature will not disappear during the daytime, and after repeated iterations, the cells will die and the leaves will die.
4. The lobes between the veins, the tabby leaves. At low temperatures, the main veins of the leaves of vegetables will have chlorotic yellowing or bulging symptoms, and the fruit will be blocked and grow slowly. This is due to the fact that the night temperature is too low and the carbohydrates produced by photosynthesis cannot be moved to the outside in time and deposited in the leaves. If the temperature rises for a while and the carbohydrates are smoothly and fully converted, the fruit will expand smoothly and the leaves will slowly recover.
5. Leaves withered. The cold damage caused by persistent low temperature sometimes shows leaf chlorosis, which is manifested by the death of the leaves. This symptom is often caused by the late stage of the damage, which is caused by the failure of the cold-damaged tissue.
6. Flower topping. That is, the growth point of the plant gathers a large number of female flowers or small melons, and the plants stop growing. Flower topping is caused by the low temperature causing the photosynthetic products produced by the leaves to be blocked, and excessive retention in the leaves, making the leaves thicker and the branches of the vines shorter and unable to elongate, causing the female flowers to gather at the top of the plants.
In addition, low temperature chilling also often leads to the occurrence of malformed flowers, fruits and falling flowers.
Strengthen management and prevent cold damage
Before the cold current, vegetable farmers should pay attention to the weather forecast, strengthen prevention early, and reduce the loss of cold damage.
1. Strengthen the insulation of the shed. Doing a good job of insulation is the key to reducing chilling damage. First, open a "small stove" in front of the greenhouse to avoid low night temperatures. Most of the greenhouses now use roller blinds, but after the straw curtains are put down at night, the straw curtains on the front face of the greenhouse will not cling to the shed film, resulting in a large discount on the front face and a low night temperature. The vegetable grower can place several old haystacks in the horizontal direction in front of the greenhouse. When placing the shed in the afternoon, first cover it between the grass curtain and the shed film at the front face, so that the gap between the straw curtain and the shed film can be filled. Increase the thickness of the straw at the front face to improve the insulation effect. In addition to the external grasshopper, you can also cover the inside of the shed before the greenhouse, covering a layer of non-woven fabric about two meters wide, close to the front face soil, can effectively prevent cold air outside the shed to affect the shed, reduce the heat in the shed Lost to achieve the purpose of night insulation. The second is to cover the grasshopper and floating film, and the second membrane insulation is set in the shed. When the cold wave hits and the temperature is lowered, the vegetable farmer can put the old grasshopper and the old shed film replaced in the previous year on the shed after the shed, and then cover the floating film, which is equivalent to wearing a cotton quilt for the greenhouse. Thereby avoiding low night temperatures. In addition, the installation of two membranes in the shed is also a good measure for cold insulation. According to the practice of vegetable growers, after the two membranes are installed in the shed, the heat preservation effect is greatly improved. After entering the shed in the morning, it is 2-4 °C higher than before.
2. Properly pour small water to increase soil moisture and increase heat storage in the shed. The vegetable grower can properly pour small water, increase the soil moisture, and use the characteristics of moisture greater than heat and slow heat dissipation to increase the heat storage in the shed and increase the night temperature in the shed. Moreover, the soil moisture content in the shed is moderate, so that the cracks in the cultivated layer are fine and the soil insulation effect is better.
3, foliar fertilizer, improve plant resistance. Vegetable growers can spray Lu Da Ge's disease-resistant nutrient solution before the cold current, and improve the plant's resistance to stress.
Remedy for vegetables after victimization
After the symptoms of chilling injury in vegetables, the vegetable farmers should take timely measures to ease.
1. Slowly raise the temperature and release the wind slowly. After the cold wave, the weather is clear, the light is strong, the temperature rises fast, and the plant has not recovered. If the temperature rises too fast, it will only increase the damage of vegetables. It is necessary to gradually increase the light and increase the temperature to ensure the gradual recovery of the leaf function. When the temperature inside the shed is too high, you must pay attention to the air outlet. Do not pull the air outlet too much, and slowly lower the temperature. In order to prevent the wind from rushing, it will cause more harm.
2. Strengthen the management of fertilizer and water. After the plants are damaged by cold, do not immediately water and topdress, or 3-4 days after the weather turns better, the glycan peptide bio-potassium is applied. In addition, attention should be paid to foliar top dressing, which can spray 800 times of animal protease, 500 times of total nutrient foliar fertilizer and 100 times of white sugar immediately after being damaged. It can improve the nutritional status of crops and increase the concentration of cell tissue fluid. The plant is resistant to cold and frost and promotes growth.
3, moderate shading. After the plants are cold, when the weather is fine, if the light is directly irradiated, the tissue will quickly lose water and shrink and wilting. When the situation is serious, the plants will die. Therefore, it is necessary to shield it, reduce the intensity of sunlight, and avoid heating too fast.
It is expected that the temperature in the eastern region will fall in the next week, there will be snowfall or even heavy blizzard in the north and northeast, and farmers should keep an eye on the weather forecast and be prepared before cooling down and snowfall!
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