1. Different arches and different sizes of vents
The size of the vents in spring cannot be completely defined by a certain data, because the structure of the greenhouse is different, and the cooling time and speed are also different. For greenhouses with larger arches, because the arch of the greenhouse surface is suitable, the hot air flow can easily be discharged along the upper part of the greenhouse film, even if the vents are small, a better ventilation effect can be achieved. For low old greenhouses with a long planting period, because the greenhouse arch is small and the greenhouse surface is flat, the speed of the hot air flow in the greenhouse being discharged from the vents is slow, and the temperature in the greenhouse is high. Under normal circumstances, such a greenhouse opens the top vent to 40 cm wide, which has the same ventilation effect as the vents of greenhouses with higher heights and larger arches opened to 30 cm.
2. Pay more attention to ventilation in batches in spring
After opening the greenhouse for 1 hour in the morning, open the upper vents about 3-5 cm to let a small breeze, the purpose is to discharge the moisture in the greenhouse, and at the same time replenish the carbon dioxide in the greenhouse, and replenish the raw materials for the smooth progress of photosynthesis. When the greenhouse temperature rises above 28℃, gradually open the vents to keep the temperature in the greenhouse no higher than 33℃ (for warm-loving vegetables such as cucumbers and loofahs).
3. There are many strong winds in spring, so pay attention to windproofing the vents
Increase the density of the vent ropes, and it is better to use wide cloth strips with greater friction. When this kind of cloth strip is tied with a slipknot to fix the greenhouse film, the friction is large, and the slipknot is not easily blown loose by strong winds. Many vegetable farmers use nylon ropes as windproof ropes for convenience. Because the friction is small, vegetable farmers should appropriately increase the density of nylon vent ropes and fix them to prevent the vents from being blown closed by the wind. At the same time, vegetable farmers should also pay attention to checking at any time in windy weather to prevent the vent ropes from loosening and closing the vents.
