Summer tube technology of heading lettuce

First of all, we should pay attention to fertilizer and water management. Due to high summer temperature, strong light, large ground evaporation and large crop transpiration, it is necessary to often water the soil at the initial stage of planting to keep the soil moist. Entering the rainy season from July to August, after each heavy rain, we should timely drain waterlogging and pour cold water to cool down in order to protect the leaves. In the later stage of growth, the water should be properly controlled and not watered 2-3 days before harvest to prevent cracking. Its growth period is relatively short, and chemical fertilizer is the main topdressing, but attention should be paid to the application of potash fertilizer to balance nitrogen and potassium, about 15 kg each time. Secondly, we should pay attention to the prevention and control of diseases and insect pests. The diseases of lettuce in summer are mainly downy mildew, gray mildew, Sclerotinia sclerotiorum, leaf spot and so on. Downy mildew can be sprayed with 75% chlorothalonil 600 times or 40% synergistic toxins 500 times; Botrytis cinerea can be sprayed with 50% Chlorothalonil or 50% hydantoin 1000 times. Soft rot and cracking often occur in the late stage of lettuce heading. The soft rot is mainly caused by the high temperature in the ball, so it is not too early to remove the shade shed. It is more appropriate to remove the shade shed when the average temperature of the day is below 20 ℃. The crack ball is mainly caused by too much soil moisture, so watering should be controlled in the later stage of growth. Summer cultivation, generally less or no ploughing, in order to prevent the increase of soil temperature. Weeding on the surface should be the main method for those who are not covered with plastic film. The weeds were generally weeded for 2 or 3 times in the early stage of growth. Enter August, when the temperature drops somewhat, can remove shade shed or sunshade net, enter natural growth state.