How to improve the environmental conditions inside the greenhouse

    Because the greenhouse is covered with plastic film, it forms a special microclimate that is relatively closed and different from the open field. For vegetable greenhouse cultivation, it is necessary to master the characteristics of the environment in the greenhouse, and take corresponding control measures to meet the conditions of vegetable growth and development, so as to obtain high quality and high yield.

Environmental conditions in the greenhouse:

    1. Lighting:

   It depends on the solar radiation intensity outside the shed, the optical characteristics of the covering material and the degree of pollution. The light transmittance of the new plastic film is 80-85%, and the light transmittance of the old film polluted by dust and mud is often lower than 40%. Water droplets, due to the diffusion effect of water droplets, can reduce the light in the greenhouse by 10%-20%. The scaffolding and lamination lines and the frame materials of high-stalk vegetables will block light. In greenhouse management, it is necessary to avoid and eliminate the weakening of the greenhouse as much as possible. factor of light.

    2. Temperature:

    The law of temperature change: The daily change trend of the temperature in the greenhouse is the same as that in the open field, but the temperature difference between day and night varies greatly. There is sufficient sunlight during the day. If the temperature in the film-enclosed greenhouse rises rapidly, the maximum temperature can reach 40-50 °C, which is 20 °C higher than that outside the greenhouse. Above. On cloudy and rainy days, the warming effect is poor. The minimum temperature inside the shed at night is generally 1-3°C higher than that outside the shed. The temperature inside the shed is more stable than the air temperature, usually 10-20 ℃. The temperature inside the shed also varies with different locations. The horizontal distribution is high in the middle and low on both sides, so the plants in the middle of the greenhouse are often taller than those on both sides. The longitudinal distribution of the greenhouse is that when there is sunlight during the day, the temperature is high at the top and low at the bottom, and the opposite is true at night and cloudy.

    Temperature regulation: The temperature regulation of the greenhouse is mainly carried out through ventilation and heating. The use of film stripping for ventilation is the most common method to reduce and control the temperature in the greenhouse during the day. The use of shading materials can reduce the amount of light received by the greenhouse. Prevent the temperature in the shed from being too high.

    3. Control of air humidity

The changing law of air humidity in the greenhouse: the plastic film has strong sealing, the exchange of air in the greenhouse and the outside air is hindered, and the water vapor from soil evaporation and leaf transpiration is difficult to dissipate. Therefore, the humidity in the greenhouse is high. During the day, under the condition of ventilation in the greenhouse, the greenhouse is The relative humidity of the inner air is 70-80%. It can reach more than 90% in rainy days or after irrigation. The relative humidity of the air in the shed decreases with the increase of temperature, and it is often 100% at night. The humid air in the shed condenses into The water film or water droplets are attached to the inner surface of the film or to the plants.

    4. Air composition in the shed: Due to the covering, the air flow and exchange in the shed is restricted. In the case of tall vegetable plants and lush foliage, the carbon dioxide concentration in the air in the shed changes drastically. Before sunrise in the morning, due to crop respiration and soil Released, the carbon dioxide concentration in the shed is 2-3 times higher than the concentration outside the shed, and after 8-9 o'clock, with the enhancement of leaf photosynthesis, it can be reduced to below 100PPM. Therefore, ventilation should be carried out as appropriate after sunrise. Supplement carbon dioxide in the shed in time. In addition, artificial carbon dioxide fertilization can be carried out with a concentration of 800-1000PPM, which is used after sunrise and before ventilation. Artificial carbon dioxide is used in winter and spring when the light is weak and the temperature is low, the effect of increasing production is very good Significantly.

    5. Humidity management

    The relative humidity in the greenhouse should be controlled at 70%-80% as much as possible. When the indoor humidity is high or the temperature is too low, we need to open the air vents to allow the air to flow to create a suitable humidity environment. At the same time, a certain amount of ventilation can also prevent the occurrence of diseases. When necessary, you can also use a dehumidifier to dehumidify the room.