A lot of rain and snow continues to hit! Vegetables, fruit trees and wheat should resist the late spring cold in this way!

According to the national meteorological information, it is estimated that the average temperature in northwestern Heilongjiang, southeastern North China, southern Shaanxi, most of Huang-Huai, Jianghan, Jianghan, most of Jiangnan, central and southern Guizhou, and central and northern South China will drop by 60.8 ℃. Among them, the local cooling in central Guangxi and southern Jiangxi can reach more than 10 ℃. There is heavy snow or blizzard in eastern and southern Qinghai, southern Gansu, southern Ningxia, Qinling Mountains in Shaanxi, northwest Hubei, eastern and southern Xizang, eastern Jilin and eastern Heilongjiang.

Here, the editor reminds the broad masses of farmers that the climate is changeable this spring, which is easy to cause late spring cold. The following measures are put forward for vegetables, fruit trees and winter wheat to prevent and cure the late spring cold.

1. Early spring vegetables scientifically prevent and cure late spring cold.

Low temperature chilling injury caused rotting roots, dead seedlings, falling flowers and fruits, early bolting and other harm to spring vegetables; late spring frost generally occurred in the middle and late April, causing frost on the surface of growing vegetable plants in the field. How to understand the knowledge of scientific prevention and control of late spring cold is particularly important for vegetable farmers.

[1] low temperature seedling refining

After the seedlings come out, the seedling bed should be ventilated, and the ventilation rate should be gradually increased with the warm weather, and the seedlings should be trained at low temperature in order to improve the cold resistance of seedlings and adapt to the outdoor low temperature environment.

[2] increase facilities

There are two ways to increase protection facilities: one is to erect wind barriers. The wind barrier has a blocking effect on the cold air and prevents the surface from cooling further. Second, trench planting, covering plastic film. When planting vegetables in early spring, we can use trench planting method, the ditch depth is required to exceed the height of vegetable seedlings, and then cover plastic film on the ditch.

[3] temporary heating

When the cold current comes, the production in the protected area can be temporarily heated by setting up a simple coal stove or installing electric lights in the seedling shed or production shed, so as to increase the temperature in the shed and prevent frost damage.

[4] watering well water

When the strong cold air is over, the weather is clear, there is no wind or breeze at night, and the air temperature drops rapidly, especially when the surface temperature drops below 0 ℃ and frost occurs, a large amount of well water can be poured on the ground to greatly increase the ground temperature. This method can increase the ground temperature from 0 ℃ to about 8 ℃ and avoid frost.

[5] ignite the smoke

In the frost night, smoking in the field can effectively reduce or avoid frost disasters. But we should pay attention to two points: first, the fireworks should be properly dense, so that the smoke screen can basically cover the whole garden; second, the lighting time should be appropriate, it should be lit in the windward direction, from midnight to 2-3 o'clock in the morning, until there is a smoke screen covering the ground before sunrise, which works best.

[6] timely ploughing

Ploughing before frost can reduce the degree of frost damage. Because the temperature rises gradually in spring, the border soil can better absorb and store solar heat energy after hoeing. Once the frost damage comes, because part of the heat has been accumulated in the soil, the frost can be alleviated.

[7] Prevention and control of diseases and insect pests

Low temperature and high humidity can easily lead to the breeding and spread of Botrytis cinerea. It is necessary to clean up the fallen leaves of residual plants in time and strengthen the chemical control of diseases and insect pests.

2. How to deal with the late spring cold of fruit trees

[1] pay attention to weather changes and raise awareness of prevention

Try to set up your own observation records of air temperature and ground temperature in the garden, and pay attention to weather changes and weather forecasts at any time, especially before fruit trees sprout every year, on the basis of understanding the long-term weather forecasts of local meteorological departments, pay attention to the short-term weather forecast of flowering period at any time, predict the time and intensity of frost, and take emergency precautions as soon as possible.

[2] to create a microclimatic environment conducive to the growth of fruit trees.

One is to choose a southward or southeastward slope from the leeward to the sun to avoid building a garden in lowlands and closed valleys. The second is to build a shelterbelt in the main wind direction of the orchard, which can not only effectively prevent the wind, but also raise the ground temperature and prevent frost in early spring.

[3] Emergency frost prevention measures

Freezing injury prevention

① irrigation and heat preservation: fruit trees should watch or listen to the weather forecast before and after flowering. Watering before the cold wave can reduce the ground temperature and delay flowering for 2 to 3 days.

② smoke warming: on the night of the cold wave, firewood and grass are lit around the orchard to form smoke above the orchard, which can effectively avoid the harm of cold wave and low temperature.

③ tree protection: using lime water to coat white branches, straw to cover the trunk, soil to cover the root neck and sunshade net to cover the crown and other methods to prevent fruit trees from freezing, especially the protection of young trees.

④ bundles of flowers and fruits: for fruit trees that have hung fruit in early spring, such as loquat trees, in the "late spring cold" weather, in addition to taking the above measures, the young fruit should also be bagged to keep warm to reduce the effect of freezing injury.

Anti-freezing ⑤ facilities: carefully check the greenhouse facilities for delayed cultivation of grapes, pears and oranges in the greenhouse, repair the damaged scaffolding and film mulching in time, strengthen and bind the greenhouse to prevent freezing due to film damage or being blown away by the wind. When the temperature in the shed is too low, artificial heating should be used.

Post-freeze remedy

⑴ moderate pruning: timely and appropriate pruning according to the degree of freezing damage to fruit trees. The pruning time should be carried out after the temperature rises steadily, usually from the end of February to the end of March, and the trees with severe freezing should be pruned late rather than early. According to the different degree of freezing, flexible control of the amount of pruning and objects.

⑵ spraying foliar fertilizer: choose to spray 0.3% urea plus 0.2% potassium dihydrogen phosphate or highly efficient compound foliar fertilizer on frozen orange trees from 9: 00 to 3: 00 in a sunny and warm day, once every 5 days, three times in a row to supplement nutrition.

⑶ control of diseases and insect pests: trees are prone to diseases and insect pests after freezing. It is necessary to remove withered branches and frostbitten branches in time to control diseases and insect pests in order to keep the tree healthy.

[4] innovative cultivation model

With the frequent harm of late frost, for some tree species with high output value and suitable facility cultivation, such as big cherry, peach, plum, apricot, grape, etc., we should increase the scale of facility cultivation, so as to increase the output value and effectively avoid the harm of late frost. In addition, new techniques such as grass growing, grass mulching and sprinkler irrigation are adopted in orchards, which have a significant effect on reducing the harm of late frost.

3. How to prevent and cure the late spring cold of winter wheat

In the spring winter wheat areas such as Hubei and Anhui in the middle and lower reaches of the Yangtze River, the sowing time is too early and prosperous wheat appears, and the cold in late spring is easy to freeze some young ears; the sowing time is late in the north of Huang-Huai-Hai, northwest wheat region, central Shanxi and northern Shandong, and the wheat with weak seedling condition is also vulnerable to freezing damage. The leaves of the frozen wheat seem to have been soaked, and the main stem is frozen to death, but the tillers are still alive.

[1] pre-disaster prevention measures

1] classified management: wheat fields should be classified and guided according to the characteristics of seedlings and weather changes, field management should be strengthened and the cold resistance of plants should be improved. Measures such as suppression, deep hoeing and spraying plant growth regulators should be taken to restrain the over-rapid growth and development of wheat, avoid early jointing, improve cold resistance and improve lodging resistance of wheat. The first time of fertilizing and watering in spring in prosperous wheat field can be postponed to the late stage of rising or before and after jointing.

For general wheat fields, we should "promote the combination of control and control", first suppress, and then shallow ploughing, in order to achieve the role of raising temperature and preserving soil moisture. During the rising period, appropriate amount of topdressing and watering can promote the growth of tillers and strive for more panicles. For weak seedling fields, we should give priority to "promoting", try to do early hoe, raise soil temperature, increase tiller and root, and pay attention to shallow paddling hoe to avoid root injury. After turning green, it is necessary to apply quick-acting nitrogen fertilizer combined with soil moisture, weak seedling fields as long as the soil moisture is OK, should avoid watering in early spring, so as not to reduce the soil temperature. Generally speaking, topdressing and watering is carried out in the late stage of turning green or in the early stage of getting up.

2] watering before freezing: watering before freezing is one of the most effective measures to prevent cold in late spring. Before the arrival of the severe late spring cold, the wheat fields with the risk of freezing injury must be watered in time to adjust the microclimate near the ground layer, which can significantly reduce the freezing injury.

3) increasing the application of organic fertilizer: in the jointing stage of wheat, some organic fertilizer, phosphorus fertilizer and potassium fertilizer were applied to promote root development, inhibit the growth of aboveground part of wheat seedlings and enhance the ability of cold resistance.

4] spraying regulators: spraying plant nutrients on the leaves before the cold in late spring can improve plant immunity and the ability to resist various disasters and reduce the harm.

[2] Post-disaster remedial measures

1) Fertilizer and watering: wheat is a crop with tillering characteristics. Wheat fields suffering from early spring freezing injury will not kill all tillers, and small tillering buds can grow into tillers into spikes. As long as the management is strengthened, a good harvest can still be obtained. Wheat suffering from freezing injury in early spring should immediately apply available nitrogen fertilizer and watering. The synergistic effect of nitrogen and water can promote early tillering, small tillers to catch up with large tillers, increase the panicle rate of tillers and increase the number of spikes per mu, so as to reduce the loss of freezing injury. Generally, about 10 kg of urea is applied per mu.

2) ploughing to preserve soil moisture: increase the soil temperature, increase the number of tillers and obtain a good harvest.

3) spraying foliar fertilizer: spraying plant cell membrane stabilizer on wheat leaves in time after freezing can obviously promote the growth of wheat, such as the rapid growth of medium and small tillers and the rapid development of latent buds.

4) do a good job in the prevention and control of diseases and insect pests: frozen wheat fields are more vulnerable to diseases and insect pests, so they should be controlled in time. Triadimefon or carbendazim can be used to control wheat sheath blight, powdery mildew and rust. Aphids can be controlled by imidacloprid spray to reduce the loss.