How to manage the seedbed well when disastrous weather occurs during the seedling-raising period

I. Cold, overcast weather: In winter and spring, there are often periods of cold weather with continuous overcast days. When raising seedlings in a sun-facing seedbed and such weather occurs, if you assume it is cold and there is no sunlight, and therefore leave the covers on for several days in a row, then suddenly uncover them once the sky clears, severe seedling collapse often occurs. This is because, in a prolonged dark environment, the seedlings consume a great deal of their internal nutrients and become very weak. If the covers are suddenly removed after the sky clears, the roots take up less water than is lost through transpiration, so the seedlings wilt and may even die. In addition, a large amount of organic fertilizer applied in the seedbed produces some harmful gases during decomposition; seedling respiration also produces a relatively large amount of carbon dioxide. If the straw mats are not removed and no air is let in for several days, harmful gases accumulate excessively, inhibiting seedling respiration and causing poisoning. When continuous cold, overcast weather occurs, in terms of seedbed management, covers such as straw mats should be removed a little later and put back a little earlier to help retain heat and let the seedlings receive more scattered light. After removing the mats, if the seedbed temperature does not drop, do not rush to put them back; if the seedbed temperature rises after removal, put the mats back at around 3 p.m.; if the seedbed temperature drops after removal, put them back as soon as they are removed, or take advantage of the higher midday temperature to remove the mats, wait a short while, and then put them back. In addition, during continuous cold, overcast weather, ventilation may be omitted.

II. Rain and snow weather: When it begins to snow during the day, cover with straw mats immediately, and sweep off the snow immediately after the snow stops. If it snows at night, sweep off the snow immediately after it stops the next day, and remove covers such as straw mats in good time. During continuous overcast and snowy days, whether or not the snow has stopped, sweep off the snow in good time, and take advantage of the midday pause in the snow to remove the mats, or remove and replace them immediately; never go several days without removing the mats. When continuous overcast and snowy days suddenly turn clear, after removing the mats, watch closely for changes in the seedlings. If wilting is found, cover with straw mats immediately, and remove them again after the seedlings recover; cover them again when they wilt, and remove the covers again after they recover. With this remove-and-cover management, it takes about 2-3 days to return to normal removal and covering. Therefore, in such situations, if shade-covering measures with straw mats are not taken, seedling collapse is very likely to occur.

III. Windy weather: In windy weather, during the day make sure the plastic film is securely fixed so it is not blown away by the wind. When covering with mats in the evening, press the straw mats down along the wind direction; if necessary, add another layer of straw mats and weight down all around to prevent the wind at night from blowing the covers away and freezing the seedlings. In north-wind weather, because a windbreak can block the cold wind, if the weather is clear, ventilation should still be provided as appropriate to avoid the seedbed temperature becoming too high.