What should be paid attention to in vegetable management in the greenhouse in snowy days?

In winter, what effect does snow have on vegetable production, especially in shed out-of-season vegetable production? What problems should we pay attention to in snowfall? This is the topic that everybody cares about commonly, show author to come to oneself only for many years in production practice a few shallow experience talk out offer everybody reference.

The author has measured the snow pressure. If the snow thickness reaches 10 cm, the pressure on each square meter of the shed surface shall be 12.5 kg. A greenhouse with a span of 8 meters and a length of 50 meters shall bear the snow area of 350 square meters. The weight of the whole shed surface receiving snow pressure is 4375 kg. Add in the weight of each straw mat pressed on the shed surface of 25 kilograms, 50 straw mats total 1250 kilograms. The weight of 10 cm thick snow plus 50 straw mats is about 5625 kg on the surface of 0.5 mu shed. Such a large pressure is difficult for ordinary skeletons to withstand, let alone those "fragile" simple sheds! Therefore, snow should be extra vigilant, to clear the snow on the shed surface at any time. In addition, for some sheds with large span, few columns and poor skeleton firmness, columns should be added in time to prevent problems before they occur.

Snowfall days can not cover grass snow days generally thick clouds, slow ground heat dissipation, wind is also small, the temperature is not too low. Especially in the central and southern parts of our province, the outside temperature is generally-2℃~-4℃ on snowy days, and the temperature in the shed room is above 0℃. In order to reduce the trouble of snow removal, prevent snow from wetting the straw mat and reduce the pressure of the straw mat on the canopy surface, the straw mat can be rolled up when it snows, and the snow can be accumulated on the canopy film. A thick layer of snow on the canopy film has a thermal insulation effect, especially if it is covered with a layer of straw mat. After the snow stops, the snow on the shed film shall be removed in time, and the straw mat shall be covered at night.

The snow at the front and around the shed can not be removed to enhance the thermal insulation of the shed. The snow accumulated at the front and around the shed at a height of about 1 meter can not be removed, because the snow will not cause pressure on the shed framework, and the thick snow layer can also play a role in heat preservation.

After snow, it is necessary to pay attention to returning to the snow. Due to the lack of direct light, the temperature of the shed is low, especially the longer the cloudy snow continues, the lower the temperature. For fruits and vegetables, when the local temperature is below 10℃, the growth and absorption of roots basically stop, and the absorption function of old roots declines rapidly, and new roots are difficult to occur. The longer the cloudy snow lasts, the greater the harm. If the weather is clear after snow, the temperature of the shed will rise rapidly if the grass is removed immediately, the light will be enhanced, the plant will transpire a lot of water outward, and the root system will be difficult to satisfy the transpiration of the leaves under the condition of extremely weak water absorption. If no measures are taken in time, the leaves will form permanent wilting that is difficult to recover, and finally lead to the death of the plant. In order to prevent this situation from happening, the grass cover should not be completely uncovered at once, and a tentative way should be adopted, that is, less uncovered first, such as 1/4 uncovered first, and after a certain period of time, if there is no abnormal reaction of the leaves, some can be uncovered again until all uncovered. If the leaves are found wilting, they should be returned in time. This multiple restorative adaptation process may last for several days. Sometimes due to the low temperature in the greenhouse for too long, the vegetable roots die too much, even if the cover is also useless, at this time it is necessary to consider the problem of replanting.

After the snow, it is clear to pay attention to the night heat preservation of the shed. After the snow, it is clear that there is no cloud cover in the sky at night, and the heat on the ground radiates outward and cools rapidly. If the greenhouse's own thermal insulation is poor, the temperature will also decrease rapidly with the decrease of external temperature, and even a low temperature close to 0℃ will occur, causing cold damage or even freezing damage to crops. Heat preservation method: First, put down the straw mat as much as possible before sunset to store some heat. The second is to increase the number of layers to reduce heat loss. Third, temporary warming to disperse cold air.

After the snow melts, the overwintering vegetables in the open field should be cultivated in time to preserve moisture, such as cauliflower, cabbage, garlic, onion, shallot and some leafy vegetables. Chemical fertilizer can be applied once after the snow melts, and the overwintering vegetables should be cultivated to preserve moisture, so as to promote the growth after spring.