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How to prevent greenhouse temperature hazards in greenhouses in winter and spring

2018-12-15

In the winter and spring seasons, due to the low temperature in the north, if the seedlings planted in greenhouses are not well insulated, there will be a phenomenon of “greenhouse inversion”, that is, the lowest temperature in the shed is lower than the lowest outside temperature. The overwintering seedlings in the greenhouse will cause serious freezing damage or death, so it will attract the attention of the majority of flower and tree growers.

There are three reasons for the inversion of temperature in the greenhouse: First, in the sunny day, the temperature of the ground in the greenhouse rises rapidly, and at night, it radiates heat through the covering and dissipates a lot. When the temperature is below 0 °C, the temperature in the greenhouse will drop below 0 °C (-1 °C or -2 °C). Second, the temperature of the leaf surface of the seedlings is higher than the temperature, and radiation can be radiated. Third, the ground temperature is generally higher than the temperature, but the soil area in the greenhouse is limited, and the heat compensation function of the soil heat to the air is small, and it is difficult to maintain a high temperature in the shed.

The inversion of the greenhouse often occurs in the sunny weather after the rainy winter and spring, and is most noticeable around midnight. To prevent the greenhouse from being warmed up, the following measures can be taken.

A small shed in the shed. This is the main warming and insulation measures for winter seedling management. The bamboo shed and the reinforced membrane can be used in the shed, and it is best to use the inner membrane every other year. It is better to cover the double-small shed film in the deep winter season, because the temperature in the shed is 2.5-3 °C higher than that in the greenhouse.

Increase the cover. At night, add straws made of dry straw or other straw around the greenhouse, which can increase the temperature of the shed by 1-2 °C than without the cover. In the cold weather, a layer of film is covered on the straw curtain to block the wind, prevent rain and snow from wetting the straw curtain, and reduce heat loss caused by evaporation of water. At night after a long rain, the cover can be added to the small arch shed in the shed to prevent the heat in the small shed from convection into the greenhouse. Covers can be used for grasshoppers, straw bags, kraft paper, rotten quilts, etc., which generally increase the temperature of the small arch shed by 1-2 °C.

Add curtains. It is possible to put grass and other grasses on the circumference of the greenhouse to reduce the heat radiation inside the shed.

Master the timing of ventilation. Multi-layer covered greenhouses heat up faster on sunny days. In order to prevent the high temperature and high humidity in the greenhouse from affecting the growth of seedlings, it is necessary to open the door to adjust the temperature and air when the temperature of the greenhouse rises above 15 °C.

Other warming measures. While using the above several methods to increase the temperature, it is necessary to cooperate with the shed to dig cold trenches to prevent groundwater from penetrating into the shed. In addition, the seedlings should be placed in the middle of the greenhouse as much as possible, and some debris can be stacked on both sides of the greenhouse to increase the temperature. Conditional heating lines, fires, and electric lamps can be installed in the greenhouse to prevent freezing damage caused by inversion.


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