Plastic film has thermal insulation properties. After covering the film, the temperature in the greenhouse will rise as the outside temperature rises, and drop as the outside temperature drops. And there are obvious seasonal changes and large temperature differences between day and night. The higher the low temperature period, the greater the temperature difference. Generally, the daily temperature increase in the greenhouse in the cold season can reach 3-6°C, and the temperature increase ability is only 1-2°C on cloudy days or night. In the warm spring season, the temperature difference between the shed and the open field gradually increases, and the temperature increase can reach 6-15 ℃. When the outside temperature rises, the temperature increase in the shed will increase, and the maximum temperature can be above 20℃. Therefore, there are high temperature and freezing hazards in the shed, and manual adjustment is required. In the high temperature season, the high temperature above 50℃ can be generated in the shed. Ventilate the whole shed. Cover the outside of the shed with a straw curtain or build a "pergola", which can be 1-2℃ lower than the open air temperature. In the winter on a sunny day, the lowest temperature at night can be 1-3°C higher than that of the open field, and on a cloudy day, several branches are the same as those in the open field. Therefore, the main production seasons for greenhouses are spring, summer and autumn. Through heat preservation and ventilation and cooling, the temperature of the shed can be kept at 15-30℃, which is the suitable temperature for growth.
When buckling the film, try to avoid mechanical damage to the shed film, especially for the bamboo frame greenhouse. Before buckling the film, flatten the protruding part of the surface of the frame, or wrap it up with an old cloth. When fixing with springs, a layer of old newspaper should be added to the slot. In addition, care should be taken to avoid long-term contact between the new and old films, so as not to accelerate the aging of the new films. Be careful when ventilating. The film is frozen or exposed to promote aging, and the temperature of the steel pipe can rise to 60-70℃ when exposed to the sun in summer, thereby accelerating the aging and breaking of the film. In the process of using the film, it is inevitable that there will be holes, so use adhesive or tape to fix it in time. 2. Environmental Features and Regulations Because the greenhouse is covered with plastic film, a special microclimate that is relatively closed and different from the open area is formed. For vegetable greenhouse cultivation, it is necessary to grasp the characteristics of the environment in the greenhouse, and take corresponding control measures to meet the conditions for vegetable growth and development, so as to obtain high-quality and high-yield.
