What are the technical measures for protecting crops from cold and frost in winter?

Generally speaking, crops are not very cold-tolerant, and in the cold winter they easily suffer frost damage, causing economic losses to farmers. So what are the technical measures for protecting crops from cold and frost in winter?

I. Technical measures for cold protection and disaster reduction in vegetables

(I) Reinforce greenhouses and remove snow to prevent collapse

In recent years, greenhouse cultivation has developed rapidly, but bamboo and wood-frame greenhouses still predominate. Depending on the quality of each greenhouse frame, greenhouses should be reinforced to improve their pressure resistance; when ice and snow arrive, the snow on the greenhouse roof should be swept off in the snow.

(II) According to conditions, do a good job of cultivating and managing vegetables still growing in open fields

1. For lettuce with swollen stems and cauliflower that has basically reached harvest stage, they should be marketed early (they suffer frost damage at -1°C).

2. For cauliflower that has already budded, first cover the curd with one old leaf, then tie the outer leaves into a bundle.

3. For cold-tolerant vegetables such as small lettuce seedlings, spinach, cilantro and flowering Chinese cabbage, choose cloudy or sunny days to spray cold-resistant and frost-resistant agents 2-3 times.

4. For radishes, hilling up soil should be strengthened.

5. Producers with the means can cover vegetables with plastic film or shade netting to prevent freezing.

(III) Strengthen the management of vegetables still growing in greenhouses

Vegetables still growing in greenhouses are mainly cold-tolerant autumn and winter varieties. The following management measures are recommended.

1. On sunny and cloudy days, open the greenhouse door, focusing mainly on reducing humidity.

2. On rainy and snowy days, close the greenhouse door, focusing mainly on keeping warm.

3. At night, close the greenhouse door, focusing mainly on keeping warm.

4. Disease and pest control: diseases are mainly gray mold and early blight, and pests are only aphids and whiteflies. Choose sunny or cloudy mornings to spray agents such as propiconazole and procymidone to prevent disease; spray imidacloprid or Beauveria bassiana to control aphids, or 1+1 Bacillus thuringiensis to control aphids or whiteflies.

(IV) Carefully handle the cultivation and management of overwintering seedlings of solanaceous vegetables. The following management measures are recommended:

1. At night, the greenhouse must be tightly covered, and small arch films should be added inside the greenhouse, but the small arch frames need a ventilation opening on each side every 10 meters, which helps reduce humidity and prevent disease.

2. When the temperature inside the greenhouse is above 5°C, uncover the small arch film all day during the day; when the temperature inside the greenhouse is above 15°C, open the doors at both ends of the greenhouse for ventilation; when the temperature inside the greenhouse is 0°C to 4°C, uncover the small arch film for 1-3 hours at noon.

3. When the temperature is below 0°C, choose noon during the day to uncover the small arch film for 30 minutes to 1 hour, and keep the small arch film closed the rest of the time, but the ventilation openings on both sides should be opened.

4. When the temperature is lower than 0°C, producers with the means can install air heating cables inside the small arch greenhouse. For each seedling bed 1-2 meters wide and 30 meters long, use one 1000W air heating cable, energize and heat for 5-10 hours (every night). If ground heating cables have already been laid, turn on the ground heating cables to energize and heat.

5. Clear snow between the greenhouses, and promptly dredge ditches around the greenhouses to drain water, so as to prevent snowmelt from seeping into the seedling beds.

II. Technical measures for cold protection and disaster reduction in citrus

1. Promptly rescue frost-cracked branches and trunks. After the snow on the trees melts, quickly restore torn trunks to their original growth position, bind the cracks with rope, and then wrap them well with plastic film strips about 2 cm wide.

2. As appropriate, use smoke and cover. To prevent one disaster after another, on sudden clear mornings from 5-8 o'clock or at night, use citrus branches, fallen leaves, sawdust, crop stalks, etc. to make smoke piles and light them to produce smoke, setting 2-3 piles per mu of citrus orchard, so that smoke fills the orchard and reduces frost damage. For newly planted young trees, it is best to cover the canopy with plastic film or rice straw to raise the temperature inside the canopy.

3. Prune in categories at the appropriate time. When frost-killed branches are easy to identify 7-10 days after snow, prune in categories, cutting off dead branches and diseased and pest-infested branches, while retaining living branches and remaining leaves as much as possible. For those that are hard to distinguish for the time being, pruning can be done in several rounds. When pruning, the cuts should be smooth, and large cuts should be coated with protective agents such as lime sulfur mixture to reduce water evaporation.

4. Fertilize promptly to promote spring shoots. After frost damage, loosen the soil and fertilize promptly, applying 50-100 grams of urea per tree each time, once every 7-10 days, for 3-5 consecutive applications, to promote new shoots and restore tree vigor.

5. Strengthen disease and pest control. After citrus frost damage, great importance should be attached to the control of gummosis, sunscald and citrus leafminer. Once disease appears, make vertical cuts in the trunk and apply 100-fold thiophanate or carbendazim solution to the cracks. After spring shoots emerge, promptly control pests such as citrus leafminer.

III. Technical measures for cold protection and disaster reduction in tea

(I) Young and mature tea plantations.

1. Carry out pruning in categories. For young tea trees without a plucking surface, different pruning methods should be adopted according to the degree of frost damage. For lightly damaged ones, generally no pruning is needed, letting them sprout naturally; for more severely damaged ones, use pruning shears to heavily prune the damaged branches at appropriate positions; for very severely damaged ones, use the collar pruning method to cut away completely frost-damaged branches and trunks, and for branches and trunks not completely damaged, cut away only the damaged parts, so as to help the tea trees recover growth more quickly. For mature tea trees that have already been plucked, different pruning methods should also be adopted according to the degree of frost damage. For lightly damaged ones, prune on the canopy surface, and when pruning, one must grasp the principle of "better shallow than deep," avoiding cutting away bud heads that can still sprout; for more severely damaged ones, carry out heavy pruning at appropriate positions; for very severely damaged ones, collar pruning can be carried out.

2. Carry out cultivation and management in categories. For tea seedlings just transplanted in the previous autumn, because the root system has not fully resumed growth, they are very easily heaved up whole by frozen soil, causing gaps between roots and soil and leading to death of the whole plant. After the soil thaws, promptly tread the soil around the seedling roots firmly so that roots and soil are in close contact, and cover with barnyard manure or dry grass, sprinkling some soil on top to avoid damage again. For young and mature tea plantations, after the return of spring, shallow tillage and weeding should be carried out, combined with applying some quick-acting nitrogen fertilizer (such as urea) and phosphorus and potassium fertilizer. Especially for young tea trees, increasing phosphorus fertilizer helps root growth. In this way, nutrients can be replenished promptly, and it can also play the role of a bud-promoting fertilizer, having a good effect on restoring vitality and enhancing bud and leaf growth.

(II) Improved variety breeding seedlings.

1. Remove snow promptly to protect sheds. As soon as the weather turns warm, all localities should organize labor to promptly clear snow from shed surfaces and fields; immediately right and restore collapsed arch sheds, minimizing the time seedlings are pressed under snow-covered sheds.

2. Dredge ditches promptly to drain water. During the process of ice and snow melting, promptly dredge compartment ditches, surrounding ditches and main ditches, ensuring that all ditches are connected, and minimizing the time snowmelt remains in the seedling beds.

3. Do a good job of smoke fumigation and covering. When snowy weather turns clear, relatively strong frost usually occurs, and at this time the damage to seedlings is very great. All localities should cover arch sheds with plastic or rice straw to prevent frost, and at the same time, in the evening, use 3-5 piles of weeds per mu for smoke fumigation to reduce frost damage.

4. Promptly prevent and control diseases. After tea seedlings suffer frost damage, they are often easily attacked by diseases. After the sky clears and ice and snow have fully melted, spray Bordeaux mixture or carbendazim once to prevent and control diseases.

IV. Technical measures for cold protection and disaster reduction in rapeseed

1. Clear the "three ditches." After ice and snow, promptly dredge the "three ditches," drain standing water from the fields, improve soil permeability, reduce the dual effects of frost damage and waterlogging damage on rapeseed, and promote restorative root growth.

2. Promptly remove frozen bolts and frozen leaves. For early bolts, leaves and yellowed or whitened dead leaves damaged by freezing, promptly remove them after the weather clears and take them out of the field, so as to promote basal branching growth and make up for frost damage losses.

3. Apply quick-acting fertilizer as a supplementary dressing. After rapeseed suffers frost damage, both leaves and roots are damaged to varying degrees. Apply fertilizer appropriately according to seedling condition to supplement nutrients and promote rapid recovery of growth. Apply 3-5 kg of urea or 10 kg of compound fertilizer per mu as a supplementary dressing, combined with spraying 100 grams of potassium dihydrogen phosphate mixed with 50 kg of water; fields with poorer growth can appropriately increase the amount.

4. Promptly prevent and control diseases. After rapeseed suffers frost damage, the plants are damaged and are prone to diseases such as sclerotinia. Promptly spray agents such as dimethachlon or prochloraz for control.

V. Protective measures for rice seedling greenhouses

1. Promptly sweep away accumulated snow;

2. Reinforce inside the greenhouse;

3. Close the greenhouse doors at both ends;

4. Adopt heating measures inside the greenhouse.