Cultivation techniques of lettuce in winter

Varieties were selected to cultivate mid-and late-mature heading lettuce with strong cold resistance. The cultivation date can be planted in solar greenhouse from mid-late November to late January and harvested from the first and middle of January to early March. Fertile sandy loam was selected for seedling breeding, which was fined and made into flat beds. Then apply 100 kg of sifted high-quality manure and 0.5 kg of potassium dihydrogen phosphate every 10 square meters, mix well, level the border surface, water, and sow seeds. Generally use dry seed sowing, can also soak seeds to accelerate budding after sowing. Dry seeds should be sowed with 75% chlorothalonil wettable powder equivalent to 0.3% of the seed weight, but should not be placed for too long. Soak the seeds in 20 ℃ lukewarm water for 7 hours, wrap them in a cloth bag, put them under 20 ℃, rinse with clean water once a day, and sprout after 3 days. Choose to sow seeds in the morning on a windless sunny day, sowing 5 grams of seeds per square meter of seedbed. After sowing, it was covered with a layer of fine soil with a thickness of 3mi 5mm. Before soil preparation, 5000 kg of rotten organic fertilizer and 30 kg of compound fertilizer were applied per mu. After turning deeply, flat beds can be made, and those covered with plastic film can be made into small high beds. Planting solar greenhouse cultivation generally row spacing of 40 cm, plant spacing of 30 cm, watering and cutting tuo before seedling, bring more soil. Open ditches or dig holes for planting, close ditches and flat beds and pour enough water for planting. After planting, the daytime temperature was kept at 20 ℃-24 ℃, and the night temperature was above 10 ℃. During the slow seedling period, the soil was ploughed and loosened for 1 time. After slowing down the seedling, the appropriate temperature should be 15 ℃-20 ℃ during the day, and the slow seedling water should be watered for 10 days after slowing down, and chemical fertilizer should be applied lightly, about 10 kg per mu. After that, ploughing again and squatting seedlings properly. About 15 days later, when the rosette leaves had grown and the heart leaves began to cover the heart, compound fertilizer or ammonium nitrate was applied for 20 kg, and topdressing was applied again during the heading period. Watering times in winter should not be too much, in case the ground temperature or humidity is too high. When entering the pilling stage, the water supply should be uniform, do not suddenly dry and wet, so as not to crack the ball or make the ball leaf open and grow. Stop watering for 5 days before harvest.