Detailed Explanation of Key Techniques for Raising Watermelon Seedlings in Winter Cultivation

Improve the insulation and heating measures of the seedling shed. Replace polyethylene film with polyvinyl chloride anti-drip film, which greatly improves insulation and anti-drip performance and can raise the shed temperature by 1-2 degrees. Temporary heating equipment such as a fire wall or heating stove should be installed in the shed. Carry out artificial heating when necessary.

Carry out low-temperature treatment on watermelon and rootstock seeds to enhance the cold resistance of seedlings

Place the seeds that have been soaked and are about to be germinated in a freezing environment at about 0 degrees for 24 hours, then place them under suitable temperature conditions for germination. When the seeds begin to show white, treat them at -1 degree for 12-18 hours each day. Then transfer to 18 degrees for 12-6 hours, for a total of 3-5 days, and then germinate each batch under suitable temperature conditions.

Strengthen management after grafting

Within 1 week after grafting is the wound healing stage; keep the shed temperature at 20-30 degrees. When the nighttime temperature is below 18 degrees, artificial heating should be carried out. The grafted seedling bed should be strictly sealed for 3-6 days to maintain a relative humidity of 100% in the bed. For the first 3 days, it must be completely shaded, with only weak scattered light allowed to pass through. On the 4th day, gradually expose to light. After 6 days, gradually ventilate. After 7 days, remove the shading material and increase the ventilation. This allows the grafted seedlings to adapt to the normal seedbed environment.

Strengthen management during severe weather

Management during continuous overcast days, rain and snow, strong cold waves, and other severe weather is an important part of successful seedling raising. Pay attention to weather forecasts and take insulation and heating measures before a cold wave arrives. During rain and snow, a second layer of film must be placed over the straw mats. During continuous overcast days, increase light as much as possible without causing freezing damage. If the bed temperature drops after uncovering the mats, the straw mats should be uncovered, and then covered before 3 p.m. If the bed temperature drops only slightly, they can be uncovered and covered as needed. Never leave the mats uncovered for several days. During rain and snow, uncover and cover the straw mats as needed during pauses in the rain and snow. If there is insufficient light for a long time, fluorescent lamps can be used for artificial supplemental lighting. After a long overcast period followed by sudden clearing, the mats should be uncovered 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 enter normal management.

7-10 days before planting, increase ventilation and lower the temperature to harden the seedlings

Keep it at 15-20 degrees during the day. Within the limit of the watermelon seedlings not suffering freezing damage, lower the nighttime temperature as much as possible, down to 8-10 degrees, so that the watermelon seedlings adapt to the environmental conditions after planting.