How to adjust the light environment in a greenhouse
Lighting conditions are an important factor in the design of various environmental factors in solar greenhouses. It is not only the conditions for fruit trees to carry out photosynthesis, but also the heat source of the greenhouse, which directly affects the indoor temperature. Therefore, the quality of winter light conditions often become an important factor affecting the success or failure of production. Many people who are engaged in the production and management of solar greenhouses have a common understanding that "not afraid of cold weather, but more cloudy days", which fully shows the importance of light for solar greenhouses. Continuous cloudy days in winter, especially if they last for a long time, often bring catastrophic losses to production
The light intensity in the greenhouse depends on the outdoor natural light intensity and the greenhouse lighting and the light transmittance of the film. Due to the shading of the arch, the absorption and reflection of light by the film, the condensation of water droplets on the film and the adsorption of dust, the light intensity in the greenhouse is significantly lower than that in the outdoor. Under normal circumstances, the indoor light intensity is equivalent to 50 percent -80 percent of the outdoor light intensity.
The distribution of light intensity in different locations in the greenhouse is also different. The horizontal distribution of light intensity in the north-south direction of the room is uneven, with strong light at the front of the room, followed by the middle, and weak light near the back wall. The purpose of hanging a reflective screen behind the cultivation bed in winter is to increase the light intensity of the area. In the east-west direction, due to the shading effect of the gables on both sides, two triangular low-light areas are formed at the east and west ends in the morning and afternoon respectively. The vertical change of light intensity shows a decreasing trend from top to bottom. Near the inner side of the film, the light intensity is generally equivalent to about 80 percent of the outdoor light intensity, while the distance from the ground 50-2500px is only about 60 percent of the outdoor light intensity.
The lighting time in the solar greenhouse is not only limited by the natural lighting time, but also greatly affected by artificial management measures. In winter, in order to keep warm, the thatch and paper have to be uncovered late and covered early, which artificially shortens the indoor lighting time. From December to January of the following year, the indoor lighting time is generally 6-8h. After entering March, the outside temperature rises, and the thatch can be opened early and late in time to ensure that the indoor lighting time is more than 6-8h.
In order to improve the lighting conditions in the greenhouse, in addition to optimizing the lighting design of the front roof and selecting films with good light transmission performance, the following measures should also be taken: first, hang a reflective screen behind the cultivation bed; Under the premise of the indoor temperature requirements of fruit trees, try to open the cover early and cover later to prolong the light time; thirdly, after the grass thatch is opened early every day, dust and grass clippings attached to the outside of the film should be promptly swept away.
