Precautions for Managing Greenhouse Vegetables on Snowy Days
What to Pay Attention to in Greenhouse Vegetable Management on Snowy Days
In winter, what impact does snowfall have on vegetable production, especially off-season vegetable production in greenhouses? What issues should be paid attention to during snowfall? This is a topic of common concern. Here the author will share some superficial experiences from years of production practice for everyone's reference.
Strictly prevent snow pressure from causing greenhouse collapse The author has measured snow pressure. If the snow thickness reaches 10 cm, each square meter of greenhouse surface bears a pressure of 12.5 kg. A greenhouse with a span of 8 m and a length of 50 m bears a snow accumulation area of 350 sq m, and the total weight of snow pressure on the entire greenhouse surface is 4375 kg. In addition, each straw mat pressed on the greenhouse surface weighs 25 kg, and 50 straw mats total 1250 kg. The weight of 10 cm thick snow plus 50 straw mats pressed on the greenhouse surface of 0.5 mu is about 5625 kg. Such great pressure is difficult for ordinary frameworks to withstand, let alone those "frail" simple greenhouses! Therefore, extra vigilance is needed on snowy days, and snow on the greenhouse surface should be removed at any time. In addition, for greenhouses with large spans, few columns, and poor framework stability, columns should be added promptly to prevent problems before they occur.
Straw mats can be left off on snowy days On snowy days, generally the clouds are thicker, the ground releases heat slowly, the wind is also light, and the temperature is not too low. Especially in the central and southern parts of our province, the outside temperature on snowy days is generally -2°C to -4°C, and the greenhouse temperature is above 0°C. In order to reduce the trouble of removing snow, prevent accumulated snow from soaking the straw mats, and reduce the pressure of the straw mats on the greenhouse surface, the straw mats can be rolled up during snowfall and the snowflakes allowed to accumulate on the greenhouse film. A thick layer of snow on the greenhouse film has an insulating effect, just like covering a layer of straw mats. After the snow stops, remove the snow on the greenhouse film in time, and cover with straw mats at night.
Snow at the front edge and around the greenhouse can be left in place to enhance the greenhouse's insulation For snow accumulated at the front edge and around the greenhouse at a height of about 1 m, it can be left in place, because this snow will not cause pressure on the greenhouse framework, and the thick snow layer can also play an insulating role.
After snow, when it suddenly clears, pay attention to putting the straw mats back On snowy days, because there is no direct sunlight, the greenhouse temperature is relatively low, and especially the longer the cloudy and snowy days continue, the lower the temperature. For fruit vegetables, when the ground temperature is below 10°C, root growth and absorption basically stop, and the absorption function of old roots declines rapidly, while new roots are difficult to form. The longer the cloudy and snowy days last, the greater the harm. After snow, when the weather clears, if the straw mats are uncovered immediately, the greenhouse temperature will rise rapidly, light will increase, and the plants will transpire a large amount of water outward, while the root system, in a state of extremely weak water absorption capacity, will find it difficult to meet the transpiration demand of the leaves. If measures are not taken in time, the leaves will form a permanent wilting that is difficult to recover from, and ultimately lead to plant death. To prevent this situation, do not uncover all the straw mats at once. A tentative method should be adopted, that is, uncover a small part first, such as uncovering 1/4 first, and after a certain time, if the leaves show no abnormal reaction, uncover some more, until all are uncovered. If the leaves are found to wilt, the straw mats should be put back in time. This recovery adaptation process of uncovering and putting back the mats may last several days. Sometimes, due to excessively long low-temperature periods in the greenhouse, too many vegetable roots die, and even putting the mats back is of no help. At this point, replanting should be considered.
After snow clears, also pay attention to nighttime insulation of the greenhouse After snow clears, at night the sky has no cloud cover, and a large amount of ground heat radiates outward and is lost, causing rapid cooling. If the greenhouse itself has poor insulation, the temperature will also drop rapidly with the drop in outside temperature, and may even approach 0°C, causing cold damage or even freezing damage to crops. Insulation methods: First, put down the straw mats before sunset in advance to store as much heat as possible. Second, increase the number of covering layers to reduce heat loss. Third, provide temporary heating to dispel the cold.
After the snow melts, overwintering open-field vegetables should be cultivated and soil moisture conserved in a timely manner For overwintering open-field vegetables such as cauliflower, cabbage, garlic, onion, scallion, and some leafy vegetables, chemical fertilizer can be applied once after the snow melts, and cultivation and soil moisture conservation should be carried out to promote growth after the beginning of spring.
Strictly prevent snow pressure from causing greenhouse collapse The author has measured snow pressure. If the snow thickness reaches 10 cm, each square meter of greenhouse surface bears a pressure of 12.5 kg. A greenhouse with a span of 8 m and a length of 50 m bears a snow accumulation area of 350 sq m, and the total weight of snow pressure on the entire greenhouse surface is 4375 kg. In addition, each straw mat pressed on the greenhouse surface weighs 25 kg, and 50 straw mats total 1250 kg. The weight of 10 cm thick snow plus 50 straw mats pressed on the greenhouse surface of 0.5 mu is about 5625 kg. Such great pressure is difficult for ordinary frameworks to withstand, let alone those "frail" simple greenhouses! Therefore, extra vigilance is needed on snowy days, and snow on the greenhouse surface should be removed at any time. In addition, for greenhouses with large spans, few columns, and poor framework stability, columns should be added promptly to prevent problems before they occur.
Straw mats can be left off on snowy days On snowy days, generally the clouds are thicker, the ground releases heat slowly, the wind is also light, and the temperature is not too low. Especially in the central and southern parts of our province, the outside temperature on snowy days is generally -2°C to -4°C, and the greenhouse temperature is above 0°C. In order to reduce the trouble of removing snow, prevent accumulated snow from soaking the straw mats, and reduce the pressure of the straw mats on the greenhouse surface, the straw mats can be rolled up during snowfall and the snowflakes allowed to accumulate on the greenhouse film. A thick layer of snow on the greenhouse film has an insulating effect, just like covering a layer of straw mats. After the snow stops, remove the snow on the greenhouse film in time, and cover with straw mats at night.
Snow at the front edge and around the greenhouse can be left in place to enhance the greenhouse's insulation For snow accumulated at the front edge and around the greenhouse at a height of about 1 m, it can be left in place, because this snow will not cause pressure on the greenhouse framework, and the thick snow layer can also play an insulating role.
After snow, when it suddenly clears, pay attention to putting the straw mats back On snowy days, because there is no direct sunlight, the greenhouse temperature is relatively low, and especially the longer the cloudy and snowy days continue, the lower the temperature. For fruit vegetables, when the ground temperature is below 10°C, root growth and absorption basically stop, and the absorption function of old roots declines rapidly, while new roots are difficult to form. The longer the cloudy and snowy days last, the greater the harm. After snow, when the weather clears, if the straw mats are uncovered immediately, the greenhouse temperature will rise rapidly, light will increase, and the plants will transpire a large amount of water outward, while the root system, in a state of extremely weak water absorption capacity, will find it difficult to meet the transpiration demand of the leaves. If measures are not taken in time, the leaves will form a permanent wilting that is difficult to recover from, and ultimately lead to plant death. To prevent this situation, do not uncover all the straw mats at once. A tentative method should be adopted, that is, uncover a small part first, such as uncovering 1/4 first, and after a certain time, if the leaves show no abnormal reaction, uncover some more, until all are uncovered. If the leaves are found to wilt, the straw mats should be put back in time. This recovery adaptation process of uncovering and putting back the mats may last several days. Sometimes, due to excessively long low-temperature periods in the greenhouse, too many vegetable roots die, and even putting the mats back is of no help. At this point, replanting should be considered.
After snow clears, also pay attention to nighttime insulation of the greenhouse After snow clears, at night the sky has no cloud cover, and a large amount of ground heat radiates outward and is lost, causing rapid cooling. If the greenhouse itself has poor insulation, the temperature will also drop rapidly with the drop in outside temperature, and may even approach 0°C, causing cold damage or even freezing damage to crops. Insulation methods: First, put down the straw mats before sunset in advance to store as much heat as possible. Second, increase the number of covering layers to reduce heat loss. Third, provide temporary heating to dispel the cold.
After the snow melts, overwintering open-field vegetables should be cultivated and soil moisture conserved in a timely manner For overwintering open-field vegetables such as cauliflower, cabbage, garlic, onion, scallion, and some leafy vegetables, chemical fertilizer can be applied once after the snow melts, and cultivation and soil moisture conservation should be carried out to promote growth after the beginning of spring.