Under direct sunlight in summer, the light intensity can reach 60000 to 100000 lux. For crops, the light saturation point of most vegetables is 30000 to 60000 lux. For example, the light saturation point of pepper is 30000 lux, that of eggplant is 40000 lux, and that of cucumber is 55000 lux. Excessive light will have a great impact on crop photosynthesis, resulting in blocked absorption of carbon dioxide, excessive respiratory intensity, etc. This is how the phenomenon of "midday rest" of photosynthesis occurs under natural conditions. Therefore, using shading nets with appropriate shading rate can not only reduce the temperature in the shed around noon, but also improve the photosynthetic efficiency of crops, killing two birds with one stone. Considering the different lighting needs of crops and the need to control the shed temperature, we must choose a shading net with appropriate shading rate. We must not be greedy for cheap and choose at will. For the pepper with low light saturation point, the shading net with high shading rate can be selected, for example, the shading rate is 50%~70%, so as to ensure that the light intensity in the shed is about 30000 lux; For the crops with high isochromatic saturation point of cucumber, the shading net with low shading rate should be selected, for example, the shading rate should be 35~50% to ensure that the light intensity in the shed is 50000 lux