Field management of pollution-free leaf lettuce

Generally, the survival of seedlings can be delayed 5-6 days after planting. After transplanting slow seedlings, lettuce can be watered and fertilized. For heading lettuce, squatting seedlings can be carried out for one week, and then water and fertilizer management can be carried out after the end of squatting seedlings. 10 kg of urea can be applied with water every 667 square meters, and the soil should be kept moist, and the application of available nitrogen fertilizer should be stopped 30 days before harvest to prevent excessive accumulation of nitrate in leaves. In addition, heading lettuce should also be sprayed with 0.2% potassium dihydrogen phosphate solution at the initial stage of heart leaf roll. Lettuce is not resistant to high temperature and humidity. When the temperature exceeds 25 ℃, ventilation and shading measures should be taken. At the same time, lettuce is afraid of waterlogging, so it is not allowed to accumulate water in the border and should be drained in time after rain. After the hot rain in summer, the garden must be watered in time. The stems and leaves of lettuce are young and succulent, so you should pay attention not to damage the stems, leaves or roots in the field, otherwise you are susceptible to diseases. In the case of high temperature and high soil moisture, when there is no dew on the leaf surface, remove the yellow, old and residual leaves near the ground to prevent infection.