Spring vegetables, under the condition of protected cultivation, the earlier the planting, the earlier the maturity period, the higher the economic benefit. Therefore, plant as early as possible in the case of multi-layer coverage in the large arch shed or the middle arch shed. In order to cope with the "cold spring" weather, temperature management should be strengthened. During cloudy days, the temperature is low during the day, and the temperature should be low at night. The temperature difference of 5℃～10℃ should be maintained. The low temperature tolerance of some crops should also be kept to a certain limit, especially the ground temperature. The 10 cm ground temperature should not be lower than 12°C for eggplants and fruits, not lower than 8°C for leafy vegetables, and not lower than 6°C for strawberries. Don't keep seedlings at low temperature within a certain temperature range. Alternate high temperature and low temperature in a suitable temperature range, which is more conducive to seedling tempering and improves cold resistance. Taking cucumber as an example, the freezing death temperature of healthy seedlings after exercise is-2℃～0℃. Without exercise and sudden cooling conditions, they will be frozen to death at 2℃～3℃, and at 3℃～5℃. Cold damage, the tempered seedlings will not have any problems in the short-term cooling of 5℃～7℃. When planting solanaceous fruits, the ground temperature of 10 cm must be stable above 10 ℃ (melons must be above 12 ℃), and you can choose to plant in the morning on a sunny day. Choose 2 to 3 sunny days after the cold current for planting. Generally, after planting, keep a high temperature for 2 to 3 days without ventilation. In the management, the opaque covering is removed and covered early, and the heat storage promotes the slowing of the seedling. If the seedlings are basically slow and grow 1-2 core leaves after 4-6 days of planting, ventilation can be carried out for a short time when the temperature reaches 26℃～30℃ in the shed at noon.
Before the arrival of the cold current, the crops in the protected area can be closed in the morning and the insulation facilities should be covered early in the evening. When the outside temperature is too low, the seedlings should be exposed late and covered early, and keep in the light for 6 to 8 hours a day. If there is a foggy day after the cold current, the protective facilities or the large arch shed covered by multi-layer film shall be opened late and early covered with opaque cover, and ventilated for a short time (20-30 minutes) at noon. If the weather is suddenly clear after the cold current, ventilate early. When the indoor temperature reaches 21℃, open the leeward vents. Open the roof vents in the solar greenhouse. As the temperature rises, the vents increase the air volume to make the indoor temperature. Gradually rising from low, it is conducive to the recovery of crops after freezing damage. Observe the performance of the plant at any time. If there is wilting, spray (water) foliar fertilizer or sweet and sour liquid (sugar + vinegar 500 times liquid) to increase the air humidity. If the plants wilt again after spraying foliar fertilizer, the insulation quilt or grass thatch can be played back. After the plants return to normal, the opaque cover will be removed and covered again in the evening. Continue to observe the plant performance on the next day. If there is wilting, in addition to increasing the amount of air release, spray a protective fungicide to prevent diseases, such as chlorothalonil or Biotec plus neophytomycin to prevent bacterial diseases. Adding vitamin B group foliar fertilizer (Returning Shenglu-Shandong Luhong Technology Co., Ltd.), or brassinolide, etc., has a good effect on *** and recovery of crops affected by freezing.
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