How to prevent frost damage in greenhouses

Pay attention to the weather forecast in a timely manner

    This is very important, everyone should remember: pay attention to the cold wave and snowfall weather forecasts on CCTV and local TV stations in a timely manner. Nowadays, everyone has smartphones, and you can set up weather reminder services on your phone. This is the most important point. Only by knowing when the cold wave is coming can we make proper preparations for prevention.

Vegetable management in protected areas before snowfall

    1. During consecutive cloudy days, it is necessary to uncover the straw mat normally to capture the precious scattered light. The timing should be adjusted to uncover one hour later and cover one hour earlier than on sunny days.

    2. Increasing the application of organic fertilizer can enhance the soil's thermal capacity, buffer the temperature drop caused by heat loss during consecutive cloudy days, and also promote the root system to improve its cold tolerance.

    3. Moderate water control is crucial for reducing the relative humidity of indoor air, and it can also create an environment with sufficient soil moisture and dry topsoil.

    4. It is recommended to use a dual-colored mulching film (black underneath and silver on top) for temperature enhancement, moisture retention, and weed control.

Take timely measures to prevent and mitigate disasters

After the issuance of cold wave and snowstorm warnings, timely disaster prevention and mitigation measures should be taken in areas that may be affected by snowstorms:

    1. Dredge the ditches, open the drainage ditches on both sides of the greenhouse, and ensure proper drainage and prevention of waterlogging after snowfall; prepare agricultural materials for disaster relief, such as drainage machinery and equipment, pesticides, fertilizers, agricultural films, greenhouse support materials, and insulation materials.

    2. Reinforce the greenhouse in advance. Support and reinforce the roof of the greenhouse with a bamboo or other supports along the longitudinal central axis of the large (or medium) greenhouse frame at intervals of 2-3 meters, to improve the compressive strength of the greenhouse frame and prevent the greenhouse from being collapsed by heavy snow.

    When a snowstorm and cold wave warning is issued, someone should be on duty day and night to check and promptly remove the snow from the top of the greenhouse. When it snows, straw mats or insulation quilts should be promptly put in place, covered with cold-resistant film, and the greenhouse door should be tightly closed. A thin film should be added to block the air inlet to prevent cold winds from entering.

    4. In the event of a sudden snowstorm, when the snow on the shed roof cannot be cleared (especially for multi-span greenhouses), special emergency measures such as breaking the film to protect the frame should be adopted. Abandon the crops grown inside the shed and focus on protecting the shed frame to minimize losses. If there are external shading devices on the shed frame, the sunshade net on the external shading device should be retracted and tightened to prevent snow damage.

    When it snows, the photosynthesis of vegetable crops is very weak, and the photosynthetic products synthesized are very few. To reduce respiratory consumption, the temperature inside the greenhouse at night should be controlled to be 2°C to 3°C lower than that on a clear night.

    6. In continuous snowy weather, the respiration consumption of vegetables exceeds their photosynthesis, leading to the accumulation of a large amount of harmful gases such as carbon dioxide inside the greenhouse. Therefore, it is necessary to timely ventilate and exhaust harmful gases when the snow stops.

Emergency temperature compensation measures

    If you encounter a sudden snowstorm and temperature drop without any preparation, please take out the heaters and warming machines in your home and place them in the greenhouse. Don't say there are no wires or power strips; these are essential items for the greenhouse on ordinary days. In 2015, an agricultural base in Shanghai also experienced a once-in-three-decades temperature drop, with the temperature dropping to minus 12.5 degrees. The greenhouse did not have straw mats or insulation blankets, and only used multiple layers of covers before the temperature drop, with a total of three layers of film (not counting the double-colored mulching film). Normally, overwintering and growth are not a problem, but facing a temperature drop of more than ten degrees below zero is not feasible. Temporary heaters and heaters were used, with two placed in a half-acre greenhouse, one at each end, increasing the temperature inside the greenhouse to around 4 degrees.