Introduction to Sunscreen
Generally, leafy vegetables planted in winter and spring directly cover the surface of leafy vegetables with shading net (floating surface cover) to prevent the harm of low temperature. Because of its light weight, it is only about 45 grams per square meter, and also for the grown tall leafy vegetables
It will not crush, bend or reduce merchantability. Because it has certain permeability, the leaf surface is still dry after covering, which reduces the occurrence of disease. It also has a certain degree of transparency, and will not "cover yellow and rotten" after covering. In 1997, Henan Agricultural University carried out floating surface covering for winter celery in the basically grown greenhouse in Longtang Vegetable Park of Linying County to protect it from cold. The results showed that the celery leaves did not find a lot of ice cream when covered with floating surface under the condition of - 6 ℃ outside; However, the temperature of the single-layer shed control, especially the upper and middle leaves, has been frozen hard, and the temperature of the covered ones is 1.5 ℃ higher than that of the control.

Main purpose
Sunshade net
Sunshade net
Sunscreen is mainly used in summer, especially in the south. Some people describe it as white in winter in the north (covered with film) and black in summer in the south (covered with sunshade). Using shading net to cultivate vegetables in the south in summer has become a major technical measure for disaster prevention and protection. The application in the north is still limited to summer vegetable seedling cultivation. In summer (June to August), the main function of covering the sun screen is to prevent the exposure of the scorching sun, the impact of rainstorm, the harm of high temperature, and the spread of diseases and pests, especially to prevent the migration of pests.
After covering in summer, it can block light, rain, moisture and cool down; After covering in winter and spring, it also has a certain effect of heat preservation and humidification.
Moisturizing principle: after covering the sunshade, because of the cooling and wind-proof effect, the communication speed between the air in the cover area and the outside world is reduced, and the relative humidity of the air is significantly further increased. At noon, the maximum increase in humidity is generally 13-17%. The high humidity, the decrease in soil evaporation, and the increase in soil humidity.
The sunshade screen is made of polyethylene (HDPE), high-density polyethylene, PE, PB, PVC, recycled materials, new materials, polyethylene propylene, etc., and is characterized by strong tensile resistance, aging resistance, corrosion resistance, radiation resistance and portability after ultraviolet stabilizer and anti-oxidation treatment. It is mainly used for the protective cultivation of vegetables, coriander, flowers, edible fungi, seedlings, medicinal materials, ginseng, ganoderma lucidum and other crops, as well as the aquaculture and poultry breeding industry, which has obvious effects on increasing production.