First, we must pay attention to fertilizer and water management. Due to the high temperature in summer, strong sunlight, large evaporation on the ground, and large transpiration of crops, watering is often required in the initial stage of planting to keep the soil moist. In the rainy season of July-August, after each heavy rain, it should be drained in time and cool down with cold water to protect the leaves. Appropriate control of water in the late growth period, no watering 2 to 3 days before harvest, to prevent cracking. The growth period is shorter, and topdressing is mainly based on chemical fertilizers, but potassium fertilizer should be added to make the balance of nitrogen and potassium about 15 kg each time.
Second, we must pay attention to pest control. Diseases of lettuce in summer mainly include downy mildew and gray mold, sclerotinia and leaf spot. Downy mildew can be controlled with 75% chlorothalonil 600 times solution or 40% synergistic virucidal 500 times solution; gray mold can be controlled with 50% fast decanting or 50% acetaminophen 1000-1500 times spraying.
Later on, lettuce often has soft rot and fissure balls. The soft rot is mainly caused by the high temperature in the ball, so the shed must not be prematurely removed. It is more appropriate to remove the shed when the average temperature is below 20°C. The fission ball is mainly caused by excessive soil moisture, so watering should be controlled at the later stage of growth.
In summer cultivation, it is generally less cultivating or not cultivating, in order to prevent increased ground temperature. Uncovered plastic film shall be mainly surface weeding. Pre-growth weeding is usually 2 or 3 times. In August, when the temperature has dropped, the shade or shade net can be removed to enter the natural growth state.
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