During actual production and operation, the following principles and measures should be noted.
1. Temperature. When the greenhouse is ventilated, it must be carried out when the temperature in the greenhouse is higher than the temperature suitable for the growth of specific vegetables, so as to avoid cold or frost damage to the vegetables due to the indoor temperature being too low after the wind is released. Therefore, we must understand and master the temperature requirements of various stages of vegetable growth and development.
2. Air volume. When the greenhouse is ventilated, the principle of going from small to large, from small to many, and letting the wind go down. At the same time, we should also pay attention to adjusting the local temperature difference in the shed. In the high temperature place, ventilate relatively early and place a large air outlet; in the low temperature place, release the air relatively late and small air outlet. When closing the air vent, it should be done gradually from large to small and from large to small. In addition, when ventilating, it is necessary to prevent cold wind from blowing directly on the vegetable plants in the shed, which causes the temperature to rise and fall, resulting in freezing damage to vegetable leaves and young fruits.
3. Ventilation time. The purpose of ventilating and ventilating is to dehumidify and cool down, and to meet the carbon dioxide demand of photosynthesis of vegetables in the shed. Therefore, the ventilation time should generally be carried out when the temperature in the shed is too high, the relative humidity is high, and photosynthesis is accelerated, and it is generally started 1 to 2 hours after the curtain is opened on a sunny morning. In addition, after watering and fertilizing or spraying pesticides, ventilation should also be short-term due to increased humidity. In overcast and snowy weather, when the indoor relative humidity is high, carbon dioxide is deficient and harmful gas is accumulated, it should also be opened for a short time to release a small wind to meet the demand of vegetables for carbon dioxide and reduce the nutrient consumption in the plant. Improve plant cold resistance. If it encounters a long cloudy weather, the cover of the shed should be uncovered at intervals, and the amount of air released should be small to prevent excessive sunlight and transpiration, which will cause the vegetables to lose water and wilted.
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