1 Biological characteristics of lettuce The meat of lettuce is the main edible organ, and young leaves are also edible. Lettuce leaves contain lettuce, with a bitter taste, cool detoxification, analgesia, through milk, and facilitate the role. Lettuce likes cool climate, slightly frost-resistant, avoid high temperature. Seeds begin to germinate at temperatures above 4°C, germinate at a suitable temperature of 15 to 20°C, and germination is blocked above 30°C. High temperature season cultivation must be sowed after low temperature germination sowing seedlings; seedling growth suitable temperature is 15 ~ 20 °C, slow growth below 12 °C, 29 °C or more growth is poor; can withstand -6 °C low temperature, optimum temperature 11 ~ 18 stem and leaf growth °C, large leaf clusters, thick stalks; daily average temperature exceeding 24 °C or sunshine hours above 14h (hours) under high temperature and long daylight conditions, can easily cause premature bolting, resulting in slender fleshy stems, affecting yield and quality; The adult plants will suffer freezing injury below 0°C; the flowering and seedling period requires higher temperatures, below 0°C, flowering and obstructing. 2 species selection The variety of lettuce cultivated in summer and high temperature seasons should be heat-resistant, insensitive to high temperature and long-day sunshine, resistant to late-maturing varieties. Such as "Special heat-resistant leaf lettuce", "Summer resistance 40" round leaf bamboo shoots, "Summer resistance 38" tip leaf shoots, "Sun King 3" and so on. 3 Seeding and seedling raising techniques Since the sowing season is at a high temperature, low temperature treatment must be performed before sowing. Soak the seeds in cold water for 4~6h, wrap them with gauze, dry the water and put them into the incubator, keep the germination at 15~18°C, and pour the seeds with cold water 1~2 times every day, 3~4d when the seeds have 60% You can sow when left or right white. Sowing bed should choose a relatively cool plot, use human excrement as a base fertilizer, a good seedbed, irrigating the water, in the evening when the cool sowing, sowing l ~ 1.5g/m2, should not be too dense. After sowing, cover the fine soil 0.5cm, cover the surface of the shade net moisturizing cooling, seedlings after seedlings as seedlings 2 or 3 times, when the seedlings really leaves 2 to 3 tablets when spray cacodyme (ccc) 350mg/kg or uniconazole 5mg / kgl times, to prevent seedlings grow, awnings to be covered at night cover, 7 to 10 days before planting all dismantled for hardening seedlings, seedlings 4 to 5 true leaves when planting. 4 Cultivation Management Technology 4.1 Site Preparation and Base Fertilizer Choose a relatively cool zone, the previous crop has not been planted in the same crops and the irrigation and drainage of the two fields will be plowing, per 667m2 applied into the decomposed bar fertilizer 2000kg, compound fertilizer 20kg, superphosphate 50kg; or compound fertilizer 50kg plus Calcium Phosphate 50kg; Fuping intruded into deep ditch sorghum with a width of 1.4m and planted 4 rows. 4.2 timely planting Seedlings for 4 to 5 true leaves are suitable for colonization. Since the colonization period is a high temperature season, the plants can be planted after the temperature falls on a cloudy day or at 3 o'clock in the afternoon. On the morning of planting, the seedbeds were irrigated first, so that the roots could be wounded and rooted. Due to poor growth during the high temperature season, the plants are small, the spacing between the rows is 25cm25cm, and the root water can be poured after fixing the plants, and the grass cover is cooled and moistened. 4.3 Fertilizer Water Management The frequency of watering should be appropriately increased during the seedling period to prevent drought and promote survival. After planting and survival, topdressing seedling fertilizer applies 1500kg thin human fecal urine per 667m2; when it enters the rosette stage, the tender stem begins to enlarge, it needs sufficient nitrogen fertilizer and water, and it shall timely apply heavy fertilizer and apply human urine every 667m2. Kg, 100kg of plant ash, or 20kg of compound fertility; cultivating and weeding before fertilizing and clearing the soil after fertilization to promote rapid stalk hypertrophy. Lettuce in the stem enlargement period, the requirements of high phosphorus and potassium fertilizer, 0.2% potassium dihydrogen phosphate can be used for foliar fertilizer 1 to 2 times. In the late period of stem enlargement, if there is too much fertilizer or water, or in case of continuous rainy weather, vertical cracks are prone to occur, soft rot and sclerotia are easy to cause, and top dressing should be stopped 10 days before harvest. Lettuce is not tolerant to thick fertilizer, should be "fertilized and applied thinly" and applied between the strain and the strain, and cannot be applied to the base. 4.4 Preventing premature bolting Lettuce cultivated during the summer season is a long-day high temperature, and frequent rain, poor management, can easily lead to early bolting and plant leggy. When the plant enters into the swell period of the stem, every 5 to 7 days, spraying of Chlormequat 350 to 500 mg/kg promotes the enlargement of the stem and increases the stem weight. 4.5 Pest Control The insect pest of lettuce is mainly locusts, which can be sprayed with 10% net 2000 times. Diseases mainly include downy mildew, sclerotinia, and virus diseases. Downy mildew can be used 700 times Kelu 700 times, Sclerotinia can be used 40% saccaride net 2000 times, virus disease in combination with control of drug aphids at the same time, with 20% virus a500 spray. 5 harvest 40 to 50 days after the asparagus planting, the plant leaves are flush with the highest leaves of the outer leaves. The top of the plant is flat and has not been cut with a knife. The yield is generally 2000-3000 kg per 667m2. Disclaimer: Some articles in this website have been transferred from the Internet. 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