How to protect planted watermelons when the temperature drops across a large area in spring?

Adding a layer of plastic film to the greenhouse will provide better sealing and smaller temperature control fluctuations. The growth temperature of watermelon is between 20-30℃. Even if the watermelon seedlings are planted early and mature early, the temperature cannot reach the slow growth of the watermelon seedlings. In order to provide good temperature conditions for the watermelon seedlings to grow when they break ground in early spring, an extra layer of plastic film will help the watermelon seedlings create a higher temperature environment. The temperature of the greenhouse is very high. Even if the indoor temperature is not extremely cold, there will be no frostbite or frost damage to the watermelon seedlings. In extremely cold weather, indoor heating measures and quilt covers can be used to keep warm. Without stripping, the cold spring will have no impact on any crops in the greenhouse.

Planting watermelons in greenhouses in spring will not be in the seedling stage. Planting watermelons in greenhouses in spring is out of season. Spring has already arrived at the harvest period. If the film is not removed this time, it will have little impact on watermelon planting. Watermelons are planted in open fields. In some areas in the north, the planting season has not yet come, while in some areas it has already reached the seedling stage. Watermelons were planted early in the open field, and in some places small sheds were used. Watermelons are a rare crop. Using small sheds for watermelons, building sheds in rows as a whole, or covering each plant with a shed is the best way to prevent colds in late spring. Planting watermelons in this kind of small shed can not only effectively prevent spring cold, but also increase the temperature of the ground or small environment on the ground, so that the watermelon seedlings grow faster, bear fruit earlier, and mature earlier.

In severe cases, the root skin will rot, no new roots will grow, and the seedlings will easily wither. It is a physiological disease, mainly caused by the bed soil temperature being too low and the humidity being too high. When roots are burned, the root tips turn yellow, no new roots grow, but there is no root rot. The aboveground part grows slowly, is short, brittle and hard, does not grow trees, has small and wrinkled leaves, and easily forms small and old seedlings. The organic fertilizer is not fully decomposed, or is not fully sieved and mixed with the bed soil; excessive application of chemical fertilizers in the nutrient soil causes the concentration of the soil solution to be too high; the soil is dry and the soil temperature is too high. Weedy seedlings are also called high-footed seedlings. They have thin stems, long internodes, few leaves, thin and large leaves, light green leaves, soft tissue, underdeveloped root systems, poor disease resistance and stress resistance, and low photosynthetic levels. After planting, Seedlings are slow, survival rate is low, and fruiting is late, which also has a great impact on yield. Insufficient light, high night temperature, excessive nitrogen fertilizer and water; too high seeding density, crowded seedlings, poor ventilation; poor temperature management before and after seedling emergence, and too high bed temperature.