Detailed Explanation of Key Techniques for Winter Lettuce Cultivation

For variety selection, choose mid-to-late maturing head lettuce varieties with strong cold resistance for cultivation.

Cultivation dates: For solar greenhouse cultivation, planting can be done from11mid-to-late month to the following year's1late month,1harvest from early-to-mid month to3early month.

Seedling raising: Choose fertile sandy loam soil, break it up finely and make flat beds. Then apply per10square meter sieved high-quality manure100kg, potassium dihydrogen phosphate0．5kg, mix thoroughly, level the bed surface and water it, then scatter seeds after the water seeps down. Generally, dry seeds are sown, but seeds can also be soaked and pre-germinated before sowing. When sowing dry seeds, first treat them with0．3% of the seed weight using75% chlorothalonil wettable powder, but do not leave them for too long. For soaking and pre-germination, first soak in20°C warm water for6~7hours, remove and wrap in a cloth bag, place at20°C for pre-germination, rinse with clean water1times daily,2~3days until sprouts are fully emerged. Sow on a windless sunny morning, sowing per square meter of seedbed3~5grams of seeds. After sowing, cover with a layer of3~5millimeters of fine soil.

Land preparation and fertilization: Before planting, apply per mu decomposed organic fertilizer5000kg, compound fertilizer30~40kg. After deep plowing, make flat beds; for plastic film mulching, small raised beds can be made.

Planting: For solar greenhouse cultivation, generally row spacing is40cm, plant spacing is30cm. Water before lifting seedlings and cut into soil blocks, keeping more soil attached. Plant in furrows or holes, close the furrow and level the bed, then water thoroughly after planting.

Post-planting management: After planting, maintain daytime temperature at20℃~24°C, nighttime temperature above10°C. During the seedling recovery period, cultivate and loosen the soil1~2times. After seedling recovery, lower the temperature appropriately, with daytime at15℃~20°C, and7~10days after seedling recovery water for recovery, while lightly applying chemical fertilizer, about10kg per mu. Then cultivate again and appropriately control growth. About15days later, when rosette leaves have grown and the heart leaves begin to head, apply compound fertilizer or ammonium nitrate15~20kg, and apply additional fertilizer1times during the heading stage. In winter, watering frequency should not be too much, to prevent lowering soil temperature or excessive humidity. When entering the heading stage, water supply should be uniform, avoiding alternating dry and wet, to prevent head splitting or loose leaf growth. Stop watering3~5days before harvest.