Key Techniques for Raising Watermelon Seedlings in Greenhouses in Winter
1. Improve the insulation and heating measures of the seedling greenhouse. Use New High-Fat Film instead of polyethylene film, which greatly improves insulation and performance and can raise the greenhouse temperature by 1°C~2°C. The greenhouse should be equipped with temporary heating equipment such as a fire wall or heating stove. Provide artificial heating when necessary.
2. Subject watermelon and rootstock seeds to low-temperature treatment. Soak the seeds with New High-Fat Film to enhance the cold resistance of the seedlings. Place the seeds that are about to be germinated after soaking in a freezing environment of about 0°C for 24 hours, then place them under suitable temperature conditions for germination. When the seeds begin to sprout, treat them at -1°C for 12~18 hours each day. Then transfer them to 18°C for 12~6 hours, for a total treatment of 3~5 days, and then place them under suitable temperature conditions for germination.
3. Strengthen management after grafting. Within 1 week after grafting is the wound healing stage, and the greenhouse temperature should be kept at 20°C~30°C. When the nighttime temperature is below 18°C, artificial spraying of New High-Fat Film should be carried out to increase temperature. The grafted seedling bed should be strictly sealed for 3~6 days to maintain the relative temperature inside the bed. During the first 3 days, it must be fully shaded, with only weak scattered light allowed to pass through. On the 4th day, gradually expose them to light. After 6 days, gradually ventilate. After the 7th day, remove the shading material and increase the ventilation. This helps the grafted seedlings adapt to the normal seedbed environment.
4. Strengthen management during severe weather. Management during severe weather such as prolonged overcast, rain and snow, and strong cold waves is an important part of successful seedling raising. Pay attention to weather forecasts and take insulation and heating measures before the cold wave arrives. During rain and snow, a second layer of film must be placed over the straw mats. During prolonged overcast days, increase light as much as possible without causing cold damage. If the bed temperature drops after the straw mats are uncovered, they should be uncovered, then covered again before 3 p.m. If the bed temperature drops only slightly, they can be uncovered and covered as needed. Never leave the straw mats uncovered for several days. During rain or snow, uncover and cover the straw mats as needed during breaks in the rain or snow. If light is insufficient for a long time, fluorescent lamps can be used for artificial supplemental lighting. After a long period of overcast weather followed by sudden clearing, uncover the straw mats slowly, otherwise it may easily cause seedling scorching or even seedling collapse. If the seedlings are found to be wilting, cover them with shade immediately, and uncover again after the watermelon seedlings return to normal. Repeat this several times until they no longer wilt. Then uncover all the straw mats, and afterward proceed with normal management. Sun Shuli