What are the countermeasures for vegetable production in low temperature, rain and snow weather?

The weather forecast of the Central Meteorological Observatory shows that recently, due to the joint influence of eastward moving south branch trough and cold air, strong low temperature, rain and snow weather processes appear in southwest China, eastern northwest China, North China, Northeast China, Huanghuai, Jianghan, Jianghuai and other regions. The process of cooling rain and snow covers a wide range, but the duration is short and the cooling range is small, which is conducive to winter wheat overwintering safely, has little impact on perennial cash crops such as fruit trees and tea leaves, but brings adverse impact on vegetable production, especially facility vegetable production. In order to guide all localities to mitigate the impact of disasters, rapidly resume production and ensure stable supply, the National Agricultural Technology Extension Service Center and the Vegetable Expert Guidance Group of the Ministry of Agriculture and Rural Affairs have studied and put forward the following technical guidance opinions.

1. Technical measures for preventing low-temperature snowfall of open-field vegetables

(i) Thermal insulation against cold. For vegetable fields that can be cultivated, when low temperature, snow, freezing or cold current arrives, soil can be cultivated beside vegetable roots through cultivation to effectively loosen soil, prevent root system from being frostbitten, promote root system growth and ensure root system vitality. Before the cold wave or rain and snow strikes, plastic film, nonwoven fabric or sunshade net can be used to cover the cold; after the cold wave, it is necessary to continue to strengthen the cover to delay the freeze-thaw process and prevent the vegetables from freezing.

(ii) Dehumidification and decontamination. In winter, the groundwater level is relatively high. In case of rain and snow, the soil humidity increases. Vegetables in the field, especially those in the open field, are easy to rot roots, dead seedlings and rotten vegetables. It is necessary to clear the ditch and manage the soil moisture in time to prevent ponding in the field.

(c) Strong plants. Before the cold current, rain and snow come, we can supplement the middle and trace elements urgently needed by plants by spraying chitin, alginic acid and other full-nutrient foliar fertilizers and plant-derived growth regulators, which can not only avoid insufficient nutrition supply, but also improve the cold resistance of vegetable plants and reduce the occurrence of rotten vegetables and frostbite.

II. Technical measures for preventing low temperature snowfall of vegetables

In winter, the temperature is low, the light is insufficient, in case of cold wave and snowy weather, the vegetables in facilities are easy to suffer from cold damage and freezing damage, so corresponding measures shall be taken in time.

(i) Shelter reinforcement. In order to prevent snow from crushing the structure of the facilities, it is necessary to timely check the greenhouse framework, and repair the steel pipe seriously corroded or the bamboo pole aged and broken in time. The shed with poor snow pressure resistance should be reinforced and renovated by adding columns as soon as possible. For the earth wall solar greenhouse behind the roof should be covered with film to prevent snow infiltration damage to the wall.

(2) Strengthen insulation. The shed is covered with insulation blanket, straw mat and other materials, and covered with a layer of plastic film to prevent the insulation material from absorbing water and reducing the insulation effect. A simple middle shed and a small arch shed are built in the shed to form a multi-layer cover to reduce heat loss. Shed around, after the wall and shed feet to increase the cover of multi-layer straw (curtain), can effectively prevent wind insulation. Buffering films are arranged at the vents and the door of the greenhouse, or multi-layer covering is adopted for heat preservation.

(c) Prepare for heating. Prepare bath bully heat conversion bulb, electric heater, automatic heating fan, air heating wire, electric blast furnace, emergency warming fuel block, oil hot air stove, stove and other auxiliary heating items, so as to temporarily warm up when cold wave strikes.

(c) Increased lighting. Before rain or snow, it is necessary to clean up the fog droplets and dust on the shed film in time to ensure the transparency of the shed film; clean up the old leaves and sick leaves to increase the scattered light among the plants; at the same time, hang a reflective curtain on the back wall of the greenhouse. Multi-layer coverage and cold weather are easy to cause insufficient light. In areas where conditions permit, plant growth lamps, LED lamps, iodine tungsten lamps, sodium lamps and other supplementary light equipment shall be prepared in time, and appropriate supplementary light shall be provided if necessary.

(v) Appropriate fertilization. Before cold wave and rainy and snowy weather, organic fertilizer should be added, such as pig manure, cow dung and compost; medium and trace element fertilizers such as magnesium, zinc and boron should be moderately added; quick-acting nitrogen fertilizer should not be applied, but 0.3% potassium dihydrogen phosphate solution can be sprayed on leaves for 2~3 times to improve plant resistance.

(b) Control of watering. It is strictly prohibited to water in the low temperature period before the arrival of rainy and snowy weather, so as not to reduce the ground temperature and aggravate the cold damage and freezing damage; it is necessary to achieve "three watering and three no watering", that is, watering in sunny days, not watering in cloudy days, watering before noon, not watering in the afternoon, watering small water and not watering large water.

(7) Reduce pruning and fork. Avoid plant wound infection in low temperature and high humidity environment.

(8) Low temperature exercise. 1~2 days before cold wave and rain and snow weather, moderate low temperature exercise management of plants, daytime and night temperature drop about 2℃ compared with normal management, help vegetable crops adapt to low temperature environment in advance, can reduce physiological obstacles such as flower and fruit drop caused by sudden drop of temperature.

(9) Prevention of diseases. Before cold wave and rainy and snowy weather, choose fine weather to spray vegetables to prevent diseases. Because spraying liquid medicine causes humidity to increase in shed, smoke agent and dust method should be selected to control diseases and insect pests. 5% chlorothalonil compound dust can be selected for prevention and control of fungal diseases; 6.5% Wanmeiling dust and 5% Shuangke dust can be selected for prevention and control of late blight and gray mold; 5% lipid copper dust can be selected for prevention and control of bacterial diseases; 45% chlorothalonil smoke agent can be selected for prevention and control of cucumber downy mildew, blight, tomato early blight, late blight and gray mold in greenhouse, 250g per mu each time; To control cucumber powdery mildew, 15% Pythium·Chlorothalonil smoke agent can be used, 250g per mu each time; to control vegetable sclerotinia sclerotiorum, 10% Pythium smoke agent can be used, 250~ 300g per mu each time.

3. Technical measures for disaster reduction after low temperature snow disaster of open field vegetables

(a) Garden management. After the snow disaster, we should strengthen the management of vegetables in the garden, clear the snow in the field in time, pay close attention to clearing ditches, draining and cultivating, reduce soil moisture and reduce the occurrence of waterlogging. For some low-lying, long ridge head, poor drainage of the field to add waist ditch, drainage drainage.

(ii) Thermal insulation and freezing. Use all kinds of materials to strengthen the preservation and freezing of open field vegetables. Overwintering leafy vegetables such as cabbage, celery, lettuce and oil wheat vegetables can be covered with non-woven fabrics, old plastic films, straw curtains and sunshade nets at night to prevent freezing damage. Plastic film cover insulation, should adopt small arch shed cover way; non-woven fabric cover insulation, should adopt floating surface cover way.

(3) Reasonable fertilization. Appropriate topdressing of phosphorus and potassium fertilizer, available 0.2% potassium dihydrogen phosphate spraying leaves, improve plant cold resistance, promote crop recovery growth as soon as possible.

(4) Timely collection. Before and after rain and snow weather, vegetables that can be harvested and listed should be harvested and listed to reduce losses.

IV. Technical measures for disaster reduction after low temperature snow disaster of vegetable facilities

(a) Remove snow. Clear the snow in time. In case of heavy snow, it shall be cleared at the same time, especially pay attention to strengthening snow removal at night. The snow thickness on the shed can also be quickly reduced by sprinkling snowmelt agent and salt to prevent the shed from collapsing. In areas where conditions permit, high-energy lamps and other methods can be used to increase the temperature in the shed and promote the melting of snow in the shed film. In case of snow during the day, cover such as straw mat should be removed as much as possible, which is not only conducive to maintaining indoor temperature and photosynthesis by scattered light, but also conducive to timely removal of snow on the shed; in case of snow at night, cover with a layer of plastic film outside the straw mat, etc., which is not only convenient for removing snow, but also can effectively avoid wetting quilts, straw mats and other covers.

(b) Temperature increase. Erect middle shed and small arch shed for multi-layer covering, and spread plant ash on the bed surface. Where conditions permit, heating wires, electric heating wires, air heating wires, stoves, hot-blast stoves, fill light and other facilities and equipment can be used to increase temperature. Temperature control measures shall be taken according to different vegetable varieties. The temperature of fruits and vegetables (tomato, pepper, eggplant, cucumber, zucchini, etc.) shall not be lower than 6℃, and shall not be lower than 5℃ for a short time; the temperature of leafy vegetables shall not be lower than 0℃.

(c) Increased lighting. The reflective curtain can be hung and the fill light can be installed to supplement the illumination; the drip removing agent can also be sprayed to increase the light transmission of the film, and the flour, soybean powder and 50-100 times of water solution (plus a small amount of neutral washing powder) are sprayed on the inner wall of the greenhouse film to achieve the drip removing effect.

(4) Ventilation and humidity reduction. After snow, cover should be removed in time, ventilation should be carried out to reduce the air humidity in the greenhouse and increase the CO2 concentration. Ventilation should be carried out at noon on a sunny day. After removing the mulch, if the vegetable wilts, it should be covered immediately, and then removed after the leaves recover. Repeat several times until it no longer wilts. If wilting is serious, spray water or 1% glucose solution or 1% alginate solution on wilted plants to restore plant growth as soon as possible.

(5) Timely prevention of diseases. Vegetables in greenhouse after snow are prone to diseases, so smoke agent and powder should be used to control them. If gray mold occurs, it can be controlled by iprodione, pyrimethanil, clerotiam, boscalid, chlorothalonil, pythalyl, thiram, etc. If sclerotium occurs, in addition to the above-mentioned drugs for controlling gray mold, it can also be controlled by vinyclidine, prochloraz, carbendazim, triadimefon, etc. At the same time, cover such as straw curtain or non-woven fabric should be opened as much as possible to reduce the humidity in the shed.

(b) Timely harvesting. Before and after rainy and snowy weather, vegetables that can be listed on the market should be harvested in time, especially hot pepper, eggplant, tomato, cucumber and other warm-loving fruits and vegetables, so as to reduce the burden on plants, keep plants healthy and improve the stress resistance of plants.

(7) Cold damage emergency. For the cold injury or slight freezing injury caused by the damage of plastic film on the roof of the shed, in addition to timely repairing the film, increasing the plastic film, covering the straw curtain and other methods to keep warm, the foliar spray of 20~25 ℃ warm water, 0.2% potassium dihydrogen phosphate solution, 0.5% urea solution and other measures can be taken to reduce the injury of the plant. After the occurrence of freezing damage, do not immediately close the shed temperature, to make the temperature rise slowly, to avoid rapid rise in temperature and frozen tissue necrosis of vegetables. At the same time, it is necessary to cut off the severely frozen stems and leaves and fruits in time.

(8) Intensify the repair of damaged facilities and rush to replant seeds. The vegetables in damaged facilities should be collected and transported in a timely manner, and efforts should be made to reduce the economic losses caused by snow disasters. For the newly planted early spring crop facilities vegetables, the dead seedlings due to disaster should be replanted in time according to the situation.