1. Low temperature germination
Summer lettuce is in the high-temperature season, so heat-resistant varieties must be selected. Promote germination before sowing, soak the seeds in cold water for 8-12 hours, and when the water absorption of the seeds reaches 70% to 80%, wrap it with wet gauze and place it in the refrigerator or in the refrigerator or hang it at a distance of 10 cm from the water surface. ℃ low temperature, after 24-28 hours of treatment, put it at 15-20 ℃ suitable temperature condition to moisturize and germinate (the germination rate can be improved if the seeds that have not passed the dormant period are exposed to the sun). After 2-3 days, most seeds can be sown .
2. Shading seedlings
Summer lettuce is sown at the end of June and the beginning of July. It is best to sow the seeds with appropriate amount of dry and fine soil before sowing, sowing 1 meter 2 area per gram of seeds, sowing water in case of drought and sowing. Shade the shade to raise seedlings, cover early and cover late on sunny days, and open all day on cloudy days to facilitate cooling and moisturizing. At the seedling stage combined with watering, apply 2-3 times of dilute water manure, and transplant it when there are 4-5 true leaves around 25 days of seedling age.
3. Transplanting method
Before planting, every 667 m2 of fertilized cooked manure 3000 kg and human and animal manure 2000 kg, digging trenches to make the border, leveling the border, the border width is 1.5-2 meters, the width of the trench is 25 cm, and the depth is 15-20 cm. In late July, choose a sunny evening. After the seedling bed is watered, the seedlings are transplanted with soil, the plant spacing is 25 cm, the row spacing is 35 cm, and 700-800 plants are planted every 667 meters. After planting, pour enough water to fix the roots, and then pour dilute water manure every 2-3 days.
4. Fertilization and watering
Summer lettuce has shallow roots and weak absorption capacity. In addition, it grows rapidly in summer and requires more fertilizer and water. Special attention should be paid to the management of heavy fertilizer water. After the seedlings are alive, apply a thin water manure every 3 to 5 days in combination with drought resistance. The stems began to swell when watering the fertilizer frequently (stop watering 10 days before harvest), and spray foliar 0.3% potassium dihydrogen phosphate 1 to 2 times. If downy mildew is found, spray metalaxyl in the early stage of the disease to prevent it. Where conditions permit, when the lettuce seals the ridges and the stems begin to become hypertrophic, spraying ketamine modifier 2 to 3 times can effectively increase the stem weight.
5. Harvesting in batches
When the summer lettuce is harvested too late, succulent stems can form flower buds, consume nutrients, form hollows, and cannot be eaten. Premature harvesting reduces production. Generally about one month after transplanting, when the stem is enlarged and the top of the stem is equal to the tip of the outer leaf, it can be harvested in batches.
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