High-yielding cultivation techniques of lettuce in four seasons

1. Variety selection: overwintering lettuce and spring lettuce select varieties with cold tolerance, strong adaptability and late bolting, such as cold-tolerant white leaf tip, cold-tolerant second white bark, bitter leaf and so on. Summer and autumn lettuce, choose heat-resistant early-maturing varieties, such as heat-resistant white leaf tip, bitter clover leaf, heat-resistant big mosaic leaf, special heat-resistant second white bark, rape and so on. 2. The sowing date is determined as follows: spring lettuce, raising seedlings in greenhouse from December to March, and open field seedlings from mid-February to late March. Summer lettuce, cultivated in open field from April to mid-May, covered with sunshade net from late May to July, direct seeded or planted with high density. Autumn lettuce, sown with sunshade net from July to September, raise seedlings and transplant. Overwintering lettuce, raising seedlings in the open field from October to November. 3. Cultivate strong seedlings: 3.1 soil preparation. Select land with high dryness and good drainage as seedbed and apply 4000-5000 kg of rotten organic fertilizer per mu or 500kg of compound fertilizer as base fertilizer 5-7 days before sowing. Turn deeply before and after soil preparation, flatten and fine, cover with plastic film and wait for sowing. 3.2 seed treatment. If the seeds are sown from May to September, it is difficult for the seeds to germinate because of the hot temperature, so they need to germinate at a low temperature before sowing. Soak the seeds in cold water for 6-7 hours, wrap them in a wet cloth and germinate at 20-25 ℃ until 80% of the seeds are white. Or soak the seeds in cold water for 1-2 hours, wrap them with a wet cloth, place them 30 cm above the water surface, sprinkle water 1-2 times a day, and germinate within 3-4 days. Also, soak the seeds for 24 hours, wrap them with a wet cloth, put them in the refrigerator or freezer, freeze them in a cool place for 24 hours, and then put them in a cool place for 2-3 days. 3.3 sow seeds. Spring lettuce, when raising seedlings and sowing in the greenhouse, first uncover the film on the seedling border, pour enough bottom water, wait for the water to seep, mix the seeds in a small amount of fine sand or fine soil, and then sow. 10 square meters of seedbed sowing seeds 25-30 grams. Cover soil 0.30-0.50 cm after sowing, cover strict film, cover sunshade net or grass cloak at night to keep warm. Raise seedlings in the open field and cover the small arch shed. Before the seedlings are unearthed, uncover the mulch late and early, which will not be ventilated and raise the bed temperature. After the seedlings were unearthed, the seedlings were properly ventilated, and the bed temperature was kept at 12-20 ℃ during the day and 5-8 ℃ at night. The sunshade net is covered early and late, 2-3 true leaves are planted once, and the seedling distance is 4-5 cm. 5-6 days before transplanting, increase ventilation to refine seedlings. Summer bamboo shoots are selected to sow seeds on cloudy days. Sow wet seed cover film in the first and middle of April-May and withdraw after emergence. From late May to early and middle July, cover the sunshade net with a small arch shed or flat shed to emergence or 2 true leaves. Cover with sunshade net to prevent Rain Water from scouring on rainy days. 10 square meters sow 5-10 grams. The seedlings in front of 2 true leaves were once, the time seedlings of 4-5 true leaves were once, and the distance between seedlings was 10 cm. Robust seedlings can also be planted with high density according to the row spacing of about 10 cm. After each seedling, fixed seedling and transplanting slow seedling, the rotten dilute dung water was applied combined with watering. Clear ditches and drain stains on rainy days, and irrigate 0.50% urea water about 15 days before planting. About 25 days after seedling setting or transplanting, young plants can be harvested and listed on the market. The bed was watered thoroughly before sowing, and after sowing, a layer of 3-4 mature pig manure residue and a thin layer of rice straw were covered, or covered with black sunshade net to sow sprouts or wet seeds. The double-layer floating surface is covered on the soil of the seedling bed before emergence, and the silver-gray sunshade net is covered after emergence. Watering fertilizer in the morning and evening, keeping the bed soil moist, weeding seedlings in time. 4. Planting and management: when planting, select loam with good drainage condition and apply 4000-5000 kg of rotten organic fertilizer per mu. It is deeply turned and flattened to make a high border 1.20-1.50 meters wide. Water the seedbed before raising the seedlings. Spring lettuce, seedling age 25-30 days, 5-6 leaves colonized, plant row spacing 20 cm × 27 cm, depth should be buried to the base of the first petiole, watering after planting. Listed by leaves, plant spacing 15 cm × 20 cm. If the cultivation is covered with plastic film, the bottom fertilizer shall be fully applied at one time, and the plastic film shall be covered, and the water shall be drained and waterproof in rainy days. Cultivation in greenhouse and open field, ploughing 1-2 times in sunny and warm weather, timely watering and topdressing, early dung watering frequently, keeping the border surface moist, when the plant is basically closed, the tender plant can be put on the market. Take the stem as the product, irrigate 15 kg of urea per mu 1-2 times. Autumn lettuce. The seedlings were planted at the age of 25 days, the row spacing was 25 cm × (30-35) cm, listed as tender plants, and the row spacing was 15 cm × 20 cm. After planting in cloudy days or in the afternoon, pour and press the water in time, and cover the sunshade net with greenhouse, small arch shed or flat shed, slow the seedlings and then withdraw. Less ploughing, shallow ploughing, watering light dung frequently, keeping the soil moist, applying 3-4 mature human and animal manure 3000-4000 kg or 15 kg urea 2-3 times per mu before and after the plant closure period. Overwintering lettuce. The fertilizer at the bottom of the seedbed should not be too sufficient. The seedlings were planted with plastic film mulching at the age of 40 days, and the row spacing was (30-35) cm × (30-40) cm. After survival, fresh dung water should be applied 1-2 times, if the adult plant is listed in the following year, attention should be paid to refining seedlings before overwintering, it is not suitable to fertilize and water too frequently, to prevent overgrowth at seedling stage, and to re-apply antifreeze fertilizer and water before freezing. The weeds were cleared in time in the next spring, and the concentration of topdressing was from small to high. After the stem base began to expand, the times of topdressing decreased and the concentration decreased. Those cultivated with plastic film and greenhouse should apply sufficient base fertilizer and pay attention to ventilation management. 5, diseases and insect pests control lettuce downy mildew, choose 75% chlorothalonil wettable powder 600-800 times, or 58% Redomir 500 times, or 40% plague wettable powder 200 times, or 72.20% Prik water 800 times, etc. Rotation spray. Lettuce virus disease, timely use omethoate or aldicarb to control aphids. At the beginning of the disease, 20% virus A wettable powder 500 times liquid, or antivirus No. 1 water agent 300 times liquid, or 83 increasing resistance agent 100 times liquid and so on are used alternately. Lettuce Sclerotinia sclerotiorum, with 70% methyl thiophanate wettable powder 700x solution, 50% Shu Ke Lin wettable powder 1500 times solution, 50% propofoin wettable powder 1000 times liquid and so on rotation use. Black spot of lettuce, spray with 1500 times of 50% prohydantoin wettable powder, 40% carbendan wettable powder, 70% ethyl phosphine manganese zinc wettable powder, 75% chlorothalonil wettable powder and so on. 6. Harvesting and seed harvesting can be put on the market at any time before the stem is fully enlarged. When the tip of lettuce and the tip of the highest leaf are usually the suitable time to harvest lettuce stem. In order to prolong the market period and delay the harvest of autumn lettuce, you can pinch off the growth point and bud by hand on a sunny day, or start at the rosette stage, spray 350,500mg / kg dwarfin 2-3 times every 5-7 days, or spray 2500 mg / kg penicillin twice every 5 days when the base is hypertrophic. For seed collection of lettuce, it is better to keep seeds of overwintering spring lettuce, and the isolation between varieties is about 1000 meters. The plants with strong growth and characteristics of this variety are selected. after intercropping, keep the row spacing of more than 33 cm square, remove the old leaves, increase fertilizer and water, cultivate soil, and promote the growth of lateral branches. Properly remove some branches during flowering, insert pillars to prevent lodging, do not lack water during flowering, reduce irrigation after flowering, 20-25 days after flowering, the leaves of the seeds are normally yellowed, the seeds are brown or silver gray, and when they produce white crown hairs, they are harvested in time.