Lettuce is loved by consumers because of its refreshing taste, rich nutrition, and health care functions. It has strong adaptability and short growth period. It is one of the best vegetables for crop cultivation and intercropping in protected areas in autumn and winter. It can be supplied off-season on the New Year's Day and Spring Festival. First, the environmental requirements. Lettuce is a semi-cold vegetable, hi warm climate conditions, the most suitable growth temperature is 18-25 °C during the day, 10-12 °C at night, but can also withstand the high temperature of 30 °C and -1 °C low temperature; hi light shade bogey, Long-day crops; suitable for moist soil conditions, intolerant of drought, especially in the ball stage require sufficient water, water shortage is a small ball, bitter. Second, select good varieties. Should choose cold resistance, disease resistance, ball type, good quality and early maturing varieties. At present, the following species are more suitable. 1, Salinas 88. The upgraded varieties introduced from the United States and selected for breeding have a growth period of about 88 days. They have strong cold resistance, strong plant growth, orderliness, few outer leaves, dark green leaves, small leaf edge cuts, firm leaf ball, and a single ball weight of 500 -800 grams, good quality. 2, 1000 wins. It has been selected from the introduced Japanese early maturing varieties and has a growing period of 70-80 days. It has outstanding cold resistance, resistance to burning, and low outer leaves. The single ball weighs about 500 grams and is of good quality. 3, the emperor. It was selected from the introduced American early-maturing varieties, with a fertility period of about 85 days, strong adaptability, good cold resistance, strong heat resistance, a single ball weight of about 500 grams, and crisp quality. Third, the appropriate sowing. New Year's Day is listed in the late August seedlings, planting in late September; Spring Festival is listed in early September seedlings, planting in early October; supply of "McDonald's" and other foreign fast food should be 80 to 100 days in advance to sow the seedlings. Fourth, nurturing strong seedlings. About 20 grams per acre is used, requiring a seedbed of 20 square meters. To prevent virus disease, soak seeds with 10% trisodium phosphate for 20 minutes before sowing. After seedlings are fertilized and flattened, they are soaked in water at the bottom. Seeds are soaked after water infiltration. The cover soil is 1 cm thick. When seedlings grow to 2-3 leaves, they are seedlings once. , spacing 7-8 cm. Adequate light at seedling stage, good temperature regulation, 18-23 °C during the day, about 10 °C at night), seedling age about 6 days when 6 leaves can be planted. V. Land preparation and planting. The sorghum is 20 centimeters high above the ground. It is 40-50 centimeters wide and 40 centimeters wide. 2, colonization. Plant two lines on the surface of the plant, spacing 40-45 cm, plant spacing 30-35 cm, 4200-5500 strains per mu, 1000 Sheng, the emperor and other species density can be larger, Salinus 88 density can be smaller. Prepare the mulching and replanting of the mulching after the hoeing, planting the mulch with the soil, and watering the vine after planting. Six, field management 1, watering. After the seedlings are regenerated, the seedlings will be sprayed for 10-15 days, and then watered once every 10 days or so. Avoid flood irrigation and excessive drought. 2, top dressing. In the early and middle period, the top dressing was applied 1-2 times, and the middle and late stages of the shoot were sprayed 2-3 times. 100-150 ml of 0.3% potassium dihydrogen phosphate solution was sprayed per mu. 3, adjust the temperature and humidity. The temperature at the seedling stage is somewhat higher, 25°C during the day and 12°C at night; the temperature difference between day and night should be appropriately increased during the ball stage, which is 22-25°C during the day and 8-10°C during the night. The indoor air humidity is suitable for 65-80%, ventilation twice a day or more. From late October to late November, sunny days can use CO2 gas fertilizer to increase CO2 concentration.
