How to improve the quality of lettuce?

How to improve the quality of lettuce? Please give guidance to lettuce planting if you want to improve the quality of lettuce, you can refer to the following methods for planting: first, the requirements for the environment: the most suitable temperature for growth is 1622 degrees Celsius during the day and 10 degrees Celsius at night, but can withstand the high temperature of 30 degrees Celsius and the low temperature of minus 1 degrees Celsius; like light, avoid shading; suitable humid soil conditions, not resistant to drought; require nitrogen, phosphorus, potassium trace elements to cooperate with supply. Second, variety selection: the temperature in the early stage of open field planting in summer and autumn is high, and the temperature in the later stage is low. It is appropriate to choose varieties such as "Jingyou No.1", "Yuhu", "Baisheng", "Emperor" and "King Caesar" which are precocious, heat-resistant and anti-bolting. Third, sowing seedlings at the right time: most areas in the suburbs of Beijing will start sowing around July 20. Cool northern areas such as Yanqing, Huairou and Miyun can sow and raise seedlings on July 5-10. They should be planted in batches according to the sales quantity, and the last batch will be around August 10. Use about 20 grams per mu and need 20 square meters of seedbed. Build a small arch shed, which is covered with agricultural film and sunshade net to cover the rain and cool down. (2) the seedlings were divided once at the 3-leaf stage, the distance was 6 ~ 8cm, the seedling age was 30 days, and 6 leaves could be planted. Fourth, land preparation and planting: 2500 kg of mature organic fertilizer or 800kg of "Yite" brand active organic fertilizer is applied per mu, which is formed into a ridged high border with a width of 80cm wide and 15cm above the ground, with a width of 50cm wide and a furrow of 40cm wide. Two rows are planted on the slope of the border surface, with a spacing of 40cm and a plant spacing of 30cm, with 4,2005,000 plants per mu. To take soil to plant, try not to hurt the root system, and water it in time after planting. Fifth, field management: avoid drought and flood irrigation, generally irrigate once every 10 days or so, and there can be no shortage of water in the core period. After slowing down the seedlings, the active organic fertilizer was applied once, 200 kg per mu, and the hole was applied near the root system; at the initial stage of Baoxin, 25 kg of special fertilizer for vegetables was applied per mu. In the middle and later stage of growth, foliar fertilizer was sprayed for 3 times with an interval of about 7 days, and the mixture of 300 times liquid of potassium dihydrogen phosphate and 500 times liquid of urea was sprayed. Click for more lettuce planting techniques click to get more vegetable planting techniques