How does lettuce grow?

How to grow lettuce? Please give a detailed description of the method of lettuce cultivation can refer to the following methods: first, soil selection. Select slightly acidic loam or clayey loam with rich organic matter, fertile soil, strong water and fertility conservation, good air permeability and convenient drainage and irrigation. Second, variety selection. Choose glass lettuce, heading lettuce, mosaic lettuce and Caesar. Third, sowing seedlings 1. Sowing date: the general sowing time of lettuce is from August to February of the following year, and the most suitable sowing time is from mid-October to mid-December; it can also be sowed from early March to early May, but the growth period is short and the yield is low. It can be cultivated in large and small shed in winter and early spring, and sunshade net or shade shed in summer. 2. Seed treatment before sowing: sowing in high temperature season, seeds must be accelerated by low temperature. The method is as follows: soak in well water for about 6 hours, scrub and pick it out, wrap it with wet gauze, accelerate germination at 15-18 ℃, or hang it in a well or store it in refrigerator (about 5 ℃) for 24 hours, then place the seeds in a cool place to moisturize and accelerate germination. You can also use "1992 ○" to accelerate germination, that is, soaking seeds with 200mg of "1992 ○" per kilogram for 24 hours before germination, lettuce seeds can be dormant for 2-3 days to sprout smoothly, and 80% of the seeds should be sowed in time when the seeds are white. 3. Sowing and raising seedlings: 1500 kg of rotten farm manure and 20 kg of superphosphate were applied per mu, and mixed evenly after ploughing. Glass lettuce is generally sown from September to January of the following year, while heading lettuce is suitable for sowing from October to December. For seedling transplanting, 20-30 square meters of seedbed and 25-30 grams of seed are needed for each mu of cultivated field. Before sowing, beat through the bottom water, mix the seeds with the same amount of wet fine sand and then reseed, covering the soil about 0.50 cm. The management of seedling stage should be strengthened, and seedlings should be divided or divided in time when 2-3 true leaves are produced. Raise seedlings in winter and spring, greenhouse or open field should pay attention to nursery bed moisturizing, control watering, to prevent excessive humidity. Summer open field seedlings, pay attention to cover with sunshade net, sunshade and rain protection, cooling and moisturizing, spray water 2-3 times a day to make the soil moist. Fourth, planting. The seedling age of glass lettuce is about 25 days, it can be planted with 4-6 true leaves, the row spacing is 14 × 18 cm, and the seedling age of heading lettuce is 30-35 days, when 5-6 true leaves are planted, the row spacing is 17 × 20 cm, and the width of border is 80-90 cm. Planting soil should apply 4000-5000 kg of organic fertilizer, 20 kg of superphosphate, or 50 kg of compound fertilizer per mu. Planting should take soil to protect the root, timely watering, planting depth to bury the root is appropriate, do not bury the heart leaf. High temperature season planting, should be in the morning of the planting day, set up the scaffolding to cover the sunshade net, transplant after 4 pm. Cultivation in winter and spring can also be covered with plastic film. In greenhouse cultivation, the daytime temperature should be controlled at 12-22 ℃. If it is too low, attention should be paid to heat preservation. If it is too high (more than 24 ℃), the greenhouse should be opened for ventilation, cooling and moisture drainage. In general, the greenhouse skirt can be opened. Fifth, field management. Lettuce needs more fertilizer, so it should be applied frequently, topdressing a small amount of available nitrogen fertilizer 5-6 days after planting, 15-20 kg per mu of compound fertilizer after 15-20 days, and 10-15 kg of compound fertilizer after 25-30 days, but human urine should not be used as topdressing in the middle and later stages. There is a large amount of water demand after planting, so it should be watered timely according to the weather and soil moisture after slow seedling, usually once every 5-7 days, and not excessive watering should be controlled in the middle and later stage. The humidity in the greenhouse should be controlled and watering should be controlled 5 days before harvest. Sixth, pest prevention and control. Lettuce is mainly caused by Sclerotinia sclerotiorum, soft rot and aphids. First of all, we should select disease-resistant varieties, start with pollution-free cultivation and management, and do a good job in prevention. The harm of aphids is mostly in autumn, winter and spring, and can be sprayed with 40% dimethoate emulsion or 2000-3000 times aphid spray. Sclerotinia sclerotiorum occurs in February-March and can be sprayed with 1000-1500 times of Sukeling wettable powder. Soft rot is easy to occur in high temperature and rainy months. Spray with 47% Garinon wettable powder 1000 times, or 77% can kill 500 times wettable powder, and stop using the medicine 15 days before harvest. Click for more lettuce planting techniques click to get more vegetable planting techniques