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 of lettuce is shorter and topdressing is mainly chemical fertilizer. However, potassium fertilizer should be added to balance the 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, viral disease and gray mold, sclerotinia and leaf spot. Downy mildew can be used 75% chlorothalonil 600 times, or 40% synergistic Ruix 500 times, 58% of methylmercury manganese zinc 500 times prevention and treatment; gray mold can be used 50% off, or 50% flutter Heine 1000 ~ 1500 times, or 50% thiophanate 500 times control; virus disease prevention and control in addition to selection of disease-resistant varieties and disease-free varieties, it should also be combined with the control of aphids, with cypermethrin, Quxie pine Or anti-invigoration and other timely control of aphids to prevent infection. In addition, attention should also be paid to the prevention and control of physiological diseases and deficiency diseases. For example, the lack of boron in lettuce often causes new leaf veins and leaf margins to grow slowly, leaf wrinkles and rewinding, and leaf color unevenness, like the symptoms of mosaic virus disease, severe leaf tip, leaf margin charred, and the growth of top buds suppressed or Withered. Therefore, we must pay attention to the application of boron, various organic fertilizers containing boron, if necessary, increase the application of borax as a base fertilizer or foliar application of boron fertilizer.
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 drops, the arbours or shade nets can be removed to enter the natural growth state.
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