How to deal with greenhouse vegetables in case of low temperature, cold wave, heavy snow and frost?

This phenomenon belongs to the category of meteorological disasters in agricultural production. Accurately speaking, planting vegetables in greenhouses is faced with low temperature disasters and snowstorms in such weather. Low temperature hazards include: freezing injury, freezing injury, freezing injury, freezing injury and late spring cold. When vegetable planting in protected areas encounters this meteorological disaster weather, the low temperature disaster degree of the same greenhouse vegetable crop is not a constant absolute temperature, but is closely related to the normal growth temperature and cooling range of greenhouse vegetables before the low temperature disaster. Vegetables grown in low temperature environment for a long time have strong low temperature tolerance, but if the temperature drop is large and fast, the low temperature disaster will be very serious. For example, the heavy snow in late spring has little effect on the northern region. Once there is a cold spring in the south of the Yangtze River, agricultural production will be greatly affected.

In our north, vegetables planted in greenhouses in winter are out of season. What should I do if I encounter cold waves, heavy snow and frost? Let's talk about the symptoms of low temperature injury to vegetables first. 1. Symptoms of greenhouse vegetable leaves suffering from low temperature disaster:

Vegetable leaves are the most direct manifestation of mild freezing injury. If the seedlings are frozen at low temperature in cotyledon stage, the cotyledon leaves will lose their green edges and appear white edges, and the temperature will return to normal, which will not affect the growth of their true leaves. After planting vegetables, if a short-term cold wave strikes and the low temperature hurts people, some leaves of the plant will be frozen into dark green and will gradually dry up, and then there will be dead spots of different sizes on the leaves. This kind of dead spot usually starts from the tip of the leaf or the weak part far away from the vein, and the color becomes lighter or only the mesophyll turns white. If the temperature in the greenhouse continues to be low, it will lead to the dead leaves of vegetables, most of which are manifested as the dead leaves and the leaf tissue can not be recovered.

Low temperature disasters usually lead to slow growth of vegetables, and the color of leaves generally turns light and yellow. When the greenhouse encounters this meteorological disaster, vegetable plants are usually caused by persistent low temperature, insufficient sunshine, abnormal photosynthesis and overall lack of nutrition. Its leaf symptoms are similar to nitrogen deficiency.

It is often mistaken for the lack of fertilizer in vegetables.

2. Symptoms of greenhouse vegetable roots suffering from low temperature disaster:

If the temperature in the greenhouse is relatively low and the ground temperature is lower than the normal growth and development temperature of the root system after planting at seedling stage, it will directly lead to the low temperature disaster of vegetables. For example, crops that like warmth, such as cucumbers and tomatoes, cannot grow new roots after suffering from low temperature disasters. Then, some damaged roots will age and die gradually.

If this kind of low temperature disaster does not belong to the cliff cooling in the greenhouse, but gradually cools down, then plant withering often occurs in continuous rainy, frosty and snowy days. At this time, the temperature in the greenhouse will not necessarily drop below 0℃. However, if the temperature is not raised for a long time, the function of vegetable roots to absorb soil nutrients will be reduced or blocked in the growth environment with low temperature and low sunshine. Then, such a long-term low-temperature disaster will cause vegetable plants to turn yellow first, and then gradually wither and die from top to bottom.

3. Symptoms of low temperature disaster at growing point of greenhouse vegetables:

Growing point is the "lifeline" of vegetable growth, and it has strong stress resistance in general. Therefore, once there are obvious problems such as freezing injury at the growing point of vegetables, it shows that vegetable plants have suffered serious low temperature disasters. Usually, the growing point of plants first shows symptoms of injury from the terminal bud, or most leaves are obviously frozen. If vegetables are planted in greenhouses, it is often a low-temperature disaster when the vegetables have just been planted and the resistance is relatively poor. Therefore, in this case, when the greenhouse heats up, if the vegetable plants cannot return to normal growth, they can only be pulled out, replanted or planted.

Low temperature disasters are particularly likely to lead to some vegetables topping. Cucumber, for example, has this problem. A large number of female flowers or small melons gather at the growing point of the plant, but the plant stops growing. Low temperature disaster is easy to cause flower topping, resulting in excessive differentiation of flower buds and an increase in the number of female flowers. However, plants are physically injured by low temperature, which can not provide effective nutrition for plants, resulting in the phenomenon that branches and vines do not elongate and female flowers gather at the top of plants.

Vegetables planted in greenhouse encounter low temperature disaster, which will directly affect production and cause a large number of flowers and fruits to lodging. Even though some flowers have been pollinated, due to the low temperature disaster, the pollen tube can not be extended normally, and the purpose of pollination can not be achieved, resulting in the phenomenon of falling flowers and fruits. Then, what defensive measures should growers take to prevent the weather changes of climate disasters such as low temperature, cold wave, heavy snow and frost? 1. Cultivate strong seedlings in advance to enhance the resistance of vegetables to the growing environment.

We know that the cold resistance of vegetable Miao Zhuang is very strong, so we should choose excellent vegetable seeds and plant them in time when raising seedlings. From sowing to planting, the management temperature of vegetable seedlings is higher at the time of emergence and higher at the slow stage of transplanting and planting; After sowing, the temperature should be controlled properly, and it should be carried out after the seedlings are delayed and planted. Appropriately increase the temperature difference between day and night, adopt large temperature difference to raise seedlings and cultivate strong seedlings.

2. Necessary low-temperature exercise.

We know that plants in nature have strong cold resistance, so there is a description that "flowers in greenhouses can't stand wind and rain", not to mention the low-temperature climate with alternating cold and warm. Under the "escort" of the greenhouse, give the vegetables in the greenhouse some proper low-temperature exercise and give them some simple low-temperature growth "training" in advance. Even if they encounter sudden low-temperature disasters in the future, their resistance will be stronger than 2℃, and their cold resistance will not be mentioned in the same breath. Therefore, it is very necessary to do some proper low-temperature exercise before the seedling and planting period of vegetables. For example, warm-loving vegetables such as cucumbers and tomatoes will not be affected by the cold wave at 0℃ in a short period of time after low-temperature exercise, while seedlings without low-temperature exercise will also be damaged by low temperature at 3℃ or even higher.

3. The timing of planting should be well grasped.

According to the local temperature and the varieties of vegetables planted, choose the appropriate stubble for planting. For example, the temperature in spring is relatively low and the ground temperature is unstable, so the planting day must be on a sunny and windless day, and necessary cold-proof measures should be taken to stabilize the ground temperature. Vegetables cultivated in greenhouse are generally planted in the soil layer where the ground temperature can reach 10㎝, and the greenhouse temperature is not lower than 5℃ at night, so it is necessary to choose a good time. After planting, we should pay attention to strengthening the measures of heating and insulation in the shed to promote the rooting of seedlings. When the weather and temperature change sharply, the seedlings successfully sown slowly have strong cold resistance and are not prone to freezing injury.

4, greenhouse to strengthen heat preservation measures.

When the cold wave strikes, rain, snow, wind and frost strike, growers should add cold-proof and warm-keeping measures to the greenhouse in time. For example, greenhouse planting can increase coverage, and setting a canopy in the greenhouse can effectively increase the temperature of the greenhouse. You can also add a shed in the greenhouse, cover the vegetables on the ground with plastic film, and temporarily cover the vegetables with straw and wheat straw, defoliation and chemical fertilizer. Can play the role of heating and keeping warm. If we hear the weather forecast, there is a fierce cold wave, and the temperature drop is very large, and greenhouse vegetables may be harmed by low temperature, then it is most effective to take some temporary heating methods (such as heating) to raise the ambient temperature in the greenhouse.

5, rational fertilization, add biological regulators to prevent.

. Proper application of phosphorus, potassium and available nitrogen fertilizer before low temperature is helpful to improve the cold resistance of vegetables. The mixed solution of potassium chloride, boric acid and ammonium phosphate can also be used as foliar fertilizer for melons and vegetables according to the varieties of vegetables planted, so as to reduce or avoid the harm of low temperature. Planters skilled in using biological regulators will also choose biological regulators such as potassium dihydrogen phosphate, urea, cytokinin, paclobutrazol and abscisic acid to improve the ability of vegetables to resist low temperature.

6. Matters needing attention in improving greenhouse lighting.

In case of heavy snow, it is necessary to clear the snow on the roof of the greenhouse in time to prevent heavy snow from ballast, which may cause potential safety hazards to the greenhouse frame. Secondly, clear the snow in time. After the weather clears up, the thermal insulation cover on the roof of the greenhouse can be removed in time to let the vegetables light up and heat up.

It should be pointed out here that:

When the awning of the shed is uncovered for lighting, it can't be completely uncovered at once, especially in snowy weather that lasts for a long time. You can tentatively uncover 25% of the plastic film first, and wait for the temperature and light in the shed to have a relatively adaptive process. If the leaves of vegetables are normal and abnormal, then the plastic film should be gradually uncovered adaptively to give the vegetables an adaptation process of heating and light. Suddenly let the sun shine directly, and the temperature will rise too fast, which will also cause the "stress reaction" of vegetables, not to mention the poor adaptability of greenhouse vegetables.

Greenhouse vegetables should be protected from cold current. First of all, we should pay attention to the recent weather forecast and prepare for the low temperature disaster according to the local weather changes and the types of vegetables planted. Growers are well prepared and targeted, which can ensure that vegetables in greenhouses will not be affected by low temperature disasters and produce fresh and healthy vegetables normally.