Planting conditions and cultivation techniques of lettuce

I. Planting conditions 1. Climatic conditions Lettuce like cold climate, the minimum temperature of seed germination is 4 °C, longer time. The optimum temperature for germination is 15 to 20°C, germination for 3 to 4 days, and germination at 30°C or more. Therefore, during the summer sowing, low temperature treatment is required to promote enzyme activity and other transformation of the seeds. The optimum temperature for the growth of stems and leaves of lettuce was 11-18°C, and the suitable temperature for the ball stage was 17-18°C. Seedlings can tolerate low temperatures of -5°C. Above 21°C, it is not easy to form leaf ball or the internal temperature of the leaf ball is too high, which causes the heart leaf to rot and rot. At temperatures above 30°C, poor growth occurs. The non-heading lettuce has a wider temperature adaptation range than the lettuce. Sensitivity to sunshine response was the most sensitive in early maturing varieties, followed by mid-maturing varieties, and late in response to late-maturing varieties. 2. Soil conditions Lettuce suitable for slightly acidic soil, planted in organic-rich soil, water conservation, strong fertility, high yield, such as planting in arid and dry soil, root development is not complete, growth is not substantial, slightly bitter taste of the dish, Poor quality. 3, water conditions Lettuce different growth period, different requirements for water, seedlings can not be dry not too wet, too dry seedlings easy to aging, too wet seedlings easy to grow long. Hair growth period, to properly control the water, the ball period of water should be sufficient, lack of water leaves, bitter taste. Do not add too much water to the late ball to prevent the occurrence of fissuring and cause disease. Second, the cultivation techniques 1, select varieties of lettuce to select the appropriate varieties, combined with protective cultivation, can achieve annual production, supply throughout the year. In early spring, many non-heading varieties with strong resistance are used, because the cultivar type is easy to twitch in the early spring, and it is not easy to be roasted in the hot summer season. 2. Seeding and Seedling Cultivation of Lettuce in Jingjin Region Seeding Period: Seedlings will be sowed in spring from February to April and harvested from May to June. Autumn seedlings will be planted from late July to late August and harvested from October to November. Annual production can be achieved and annual availability. For early sowing, non-heading varieties with strong resistance should be used. Otherwise, the variety of knotted balls is easy to twitch in the early spring and it is not easy to be sown in the summer hot season. After sowing, it can germinate at a suitable temperature of 15 to 20°C for 3 to 4 days. Because the price of lettuce seeds is more expensive, the method of seedling transplanting is generally used in production. The amount of seedlings used for general seedlings ranges from 0.75 to 1.5 kg per mu, which is appropriately diluted and seeded. One acre bed can plant 10 acres of land. In the fall, lettuce seedlings are generally seeded. First soak the seeds for 12 hours, rinse them with clean water, wrap them with wet gauze, and treat them in a low temperature environment of 5 to 6°C for two days. Wait until most of the seeds begin to bloom and then take them out. After planting, the soil should not be too thick, generally about 0.5 to 1 cm. In the summer and fall seasons, it is hot and rainy, and after the sowing, shade nets are used to cover shading. 3, planting and management of lettuce roots are not deep, should choose to maintain water, fertility and fertile soil cultivation. General planting density: the spacing of early maturing cultivars was 23 cm and 20 cm, and that of medium and late ripening was 33 cm and 24 cm. Lettuce is generally top dressing 3 to 4 times. After planting the slow-onset seedlings, a slow-onset seedling fertilizer is applied, and the fertilization concentration should be reduced. Over-winter spring lettuce is topdressed once after planting, and winter is generally not fertilized. In the spring, it is necessary to continuously apply fertilizer 2 or 3 times. 4. Diseases and Pests The main diseases of lettuce are downy mildew, soft rot, viral disease and sclerotinia. Among them, sclerotinia and soft rot are more harmful, and they are easy to attack under warm and moist conditions. Take crop rotation, appropriately reduce the planting density, do not use too much watering, and always make shallow sketches to keep the soil surface dry. Frequent cleaning of fields, detection of diseased plants, and timely removal. Clear dead leaves concentrated burned. After the onset of the disease, streptomycin and daunion ammonium can be sprayed. Chlorothalonil is sprayed every 5 to 7 days in the high-temperature and high-humidity seasons for the purpose of prevention. Insect pests mainly include aphids, thrips, and ground tigers, etc. They are controlled by omethoate and extinction and killing. 5. Harvested lettuce leaves must be timely harvested after ripening, and harvesting will affect quality later. Loose leaf lettuce can be harvested about 40 days after colonization, and the individual plant weight is 0.2-0.4 kg; the cabbage-grown lettuce can be harvested 50 days after colonization. Plant weight 0.4 to 0.5 kg. Mu yield: 1000 to 1500 kg for early maturing varieties and 2500 kg for medium and late maturing varieties.