How to grow lettuce in summer?

How to grow lettuce in summer? Please introduce the methods of planting lettuce in summer with reference to the following methods: first, select the varieties of lettuce cultivated in summer, such as Caesar, Emperor, Xialu, Green Lake, which are heat-resistant and not easy to bolting, and sow in May to June. Second, cultivate strong seedlings. 1. Soak the seeds to promote budding. The seed of lettuce is small, the direct seeding technology is difficult to master, and the emergence uniformity is poor, so it is generally used to raise seedlings and transfer load. The nursery bed should be leveled and raked fine, with 25 grams per mu and 10 square meters of seedbed area. Soak the seeds to accelerate germination before sowing. First, soak in 20 ℃ of water for 4 hours, then dry the seeds in gauze and accelerate germination under the condition of 15 ℃ ~ 20 ℃. It can also be suspended on the surface of the well to promote germination at low temperature, or placed in a refrigerator of 5 ℃ ~ 10 ℃ for 24 hours, and then put the seeds in a cool place to moisturize and germinate, and then sow after the seeds are white. 2. Sowing and raising seedlings. Before sowing, the seedling bed is watered with bottom water, and after the water seeps down, the seeds are mixed with fine sand and sown, covering 0.3 cm of fine soil, and covered with sunshade nets or Reed curtains. Generally, the seedling age is about 25 days, the soil should be kept moist at the seedling stage, the sunshade net should be removed when the seedlings spit out their hearts, and they should be watered once to prevent the young roots of the seedlings from flushing out, and a thin layer of fine soil should be covered after watering. The seedlings were fixed when two true leaves were used, weeds in the bed were pulled out at the same time, and water was watered once, and the seedlings were planted in time when the seedlings grew to 4 or 5 true leaves. Third, the high border should be combined with soil preparation and basic fertilizer before planting, with 2500 kg of rotten organic fertilizer and 25 kg of superphosphate per mu. Summer generally use small high border colonization, border width 70 cm, each border planting two rows, plant spacing 25-30 cm, colonization can choose sunny afternoon or cloudy days, with soil block planting. The best planting depth is that the soil is flush with the border surface, which can not cover the heart leaves. After planting, we should water the seedlings in time, cover the sunshade net, reduce the ground temperature, cover the sunshade net during the day, cover at night, cover on rainy days and uncover on cloudy days, so as to create a suitable growth temperature of lettuce and prevent Rain Water from scouring. 4. field management 1. Ploughing. Three to five days after planting, the soil moisture was preserved by ploughing in time, and 1-2 times of shallow ploughing was generally carried out before ridge closure to promote early root development. 2. Watering. During the growing period, watering should be uniform, small water should be watered frequently, and the surface of the border should be kept moist and not too dry and wet. 3. Topdressing. Because lettuce is mainly raw food, topdressing does not apply human manure or chicken manure, mainly chemical fertilizer, generally topdressing 3 times 4 times, 15 days after slow seedling, rosette stage, heart stage, each mu of urea 5-8 kg, with water application, but not too much, to prevent lettuce dry heartburn. During the growing period, potassium dihydrogen phosphate can be properly sprayed on the leaves to improve disease resistance and edible quality. 4. Pest control. There are few diseases and insect pests in lettuce, only a few aphids, which can be controlled in time with high-efficiency and low-toxic pesticides. 5. Because the planting density of lettuce is relatively high and the staple food is crisp and tender leaves, loose leaf balls can be harvested on the market 30 days after planting. Click for more lettuce planting techniques click to get more vegetable planting techniques