Recently, two consecutive cold waves have struck, and vegetables in northern vegetable production areas have successively experienced symptoms of low temperature hazards to varying degrees. The milder manifested as the vegetable dehydration and wilting, the severer died, and the vegetable farmers suffered greater economic losses.
It is understood that under normal circumstances, the optimum temperature for most vegetables to grow is between 13°C and 30°C. After the cold wave, the lowest temperature in some sheds in northern areas is between 0℃ and 5℃, and some are even below 0℃. Vegetables are exposed to such a low temperature environment for a long time or frequently, which is prone to abnormal conditions. Before and after the cold wave, the countermeasures are also different. Vegetable farmers are advised to treat it scientifically.
Insulation is the most important in the cold wave
After the cold wave comes, it will be accompanied by different weather conditions. At this time, vegetable farmers' response measures should also be different. Among them, heat preservation is the top priority, but the most important thing is to determine the time node for warming. When the cold wave lasts for a short time or it is still sunny after the cold wave, the temperature of the shed during the day is relatively suitable, and the temperature will be low at night, especially in the middle of the night.
When the cold wave encounters low-sunlight weather, the temperature of the shed will be low during the day and night, and as the cold wave continues, the temperature will also drop slightly.
For the vegetables in the fruiting stage, combined with the heat preservation conditions of the shed, the vegetable grower can set up a "shed in the shed", or use burning blocks, solid powder and other heating in the middle of the night.
It is worth noting that the temperature of the greenhouse has the characteristics of high temperature during the day and low temperature at night, high temperature in the first half of the night and low temperature in the middle of the night, so the lowest point of the temperature of the shed is mostly in the process of pulling up the insulation quilt from the second half of the night to the morning. Therefore, when the vegetable grower judges the lowest temperature in the shed, it should be based on the temperature of the shed before pulling up the insulation quilt in the morning. So, this is also the key time period when the shed needs additional warming.
Store temperature and lighten the burden before the cold wave
Store temperature in advance. If it is sunny after the cold wave, the temperature in the shed will increase quickly; on the contrary, if the cold wave is accompanied by low sunshine or snowy weather, the temperature in the shed will continue to be low, which has a great impact on the growth of vegetables. Therefore, before the cold wave, vegetable farmers should do a good job of storing temperature in advance. In this regard, vegetable farmers should pay attention to the weather forecast at any time, and store the temperature in the shed 2 to 3 days before the arrival of the cold wave, such as opening late and closing the air outlet early, which means that the shed always maintains a high 2℃~3℃. , Let the shed see as much light as possible and store more temperature.
Remove commodity melons in time. Low temperature and low-light conditions are unfavorable to vegetable growth. The most obvious manifestation is that the plant's metabolic activity is reduced, and the nutrient synthesis and transportation capacity are poor. Then, the overall nutrient supply of the plant is insufficient, the growth of melon strips is slow, and the probability of deformed fruit increases. Therefore, before the cold wave, vegetable farmers should remove commercial fruits and deformed fruits in advance to reduce the burden on plants. In addition, when the cold wave lasts for a long time or when the weather is accompanied by low sunshine, vegetable farmers should also reduce the number of retained fruits to ensure the rate of quality fruits.
Supplement nutrition and improve plant resistance. Similarly, before the cold wave, nutrition should be supplemented in time, mainly by foliar spraying. Vegetable farmers can choose functional foliar fertilizers such as amino acids, alginic acid, and chitin for spraying, and can also be combined with nutritional foliar Used together with fertilizer, it plays a dual role of supplementing nutrition and improving stress resistance.
Delay watering in due course. If the watering time happens to be before or after the cold wave, the vegetable grower can postpone the watering properly. Because of the cold wave, the temperature dropped sharply and the ventilation time of the shed was short. After watering, the humidity in the shed increased greatly, which is easy to form a low-temperature and high-humidity environment, which is conducive to the high incidence of diseases and limited medication, which is more conducive to the accelerated spread of diseases .
The shed environment slowly changes after the cold wave
After the cold wave, when the weather turns fine, vegetable farmers must strictly grasp the word "slow" in the management of the shed to ensure that the vegetables see the light slowly and the temperature in the shed slowly rises, leaving enough buffer time for the vegetables to avoid their harm.
Slowly see the light, slowly increase the temperature. When the weather suddenly turns clear after continuous low light, when the vegetable grower pulls up the insulation quilt in the early morning, he should first pull up 1/3-1/2 to let the vegetables see the light slowly. At the same time, in fine weather, the temperature of the shed rises quickly. Vegetable farmers also want to increase the temperature quickly to promote the normal growth of vegetables. Therefore, they will re-ventilate when the temperature of the shed is high, such as above 30°C. But this approach is wrong. Because of the low temperature and low light environment during the cold wave, the function of various tissues and organs of vegetables is poor, and the growth is slow. The sudden high temperature and strong sunlight will make the vegetables overwhelmed. Vegetables will suffer from acute wilting due to insufficient water supply. From the perspective of vegetable damage, functional leaves are the most vulnerable. Therefore, while slowly seeing the light, vegetable farmers should also let the shed temperature rise slowly, and keep the highest temperature in the shed at about 28°C.
Use water to adjust the temperature when appropriate. Vegetables should be watered once after being damaged, because watering can increase the heat capacity of the soil and stabilize the surface air temperature, which is conducive to a steady rise in temperature and restores the function of the injured tissue; or vegetable farmers can also use artificial water spraying to increase the air humidity in the shed , Stabilize the shed temperature, weaken the transpiration effect, promote the tissue to absorb water and prevent wilting.
Spray foliar fertilizer. Vegetable farmers should promptly spray foliar fertilizers on chilled plants, such as amino acids, chitin, alginic acid, etc. combined with brassinolide, which can not only improve the nutritional status of crops, but also increase the concentration of cell tissue fluid and enhance the cold resistance of plants Freezing ability to promote the recovery of growth.
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