First, the choice of species. Autumn lettuce should be selected from varieties with strong heat resistance, no late bolting, and no sensitivity to high temperatures and long days. The varieties suitable for early autumn cultivation include Chengdu rod, Erbai, Wannian, Erqingpi, etc.; suitable varieties for autumn cultivation include Nanjing Purple Peel, Hangzhou Round Leaf, Changsha Fine Tip Leaf, Loquat Hammer, Guiyang Luohan Lettuce, Shanghai Large round leaf and so on.
Second, soaking germination. Lettuce is a cool type of vegetable, the seeds begin to germinate at 4°C, and germinate fastest at 15°C. When the temperature exceeds 30°C, the germination rate is slowed down and even blocked. This is because the asparagus lettuce seeds are achene, with thick peels and seed coats, the seeds germinate at high temperatures, the respiration is vigorous, the oxygen into the embryos is insufficient, and the germination is inhibited. When germinating, the seeds should be soaked for 12 to 24 hours, then wrapped in wet sand gauze and placed in the refrigerator at a temperature of 10°C to 20°C. Seeds can also be hung in deep wells 30 to 40 cm from the surface. During germination, the seeds are washed with fresh water every day and the seeds are exposed for about 4 to 5 days.
Third, timely sowing. The sowing dates for early autumn cultivation are generally from June to July, and they can be sown late after October. Generally, it is advisable to arrange the seedlings at an average temperature of 25°C to 26°C during the ten days according to local conditions.
Fourth, nurturing strong seedlings. When sowing should be appropriate to increase the sowing amount, generally 20-25 grams per square meter seedbed sowing. Seedbed soil should be chosen loose loose fertile soil, and put the cooked pig, chicken, duck dung as basic fertilizer, fine leveling land. If the temperature is higher, water should be poured before sowing. After sowing, the seeds and soil should be mixed with the gingivae and then compacted. Finally, shade nets or rice straw should be kept moist. Spray water once a day if necessary. Remove the cover after emergence. The seedbeds can be covered with bamboo or shade nets, or they can be nursed under scaffolds or mixed with Chinese cabbage to form a cool, moist microclimate. Covered with bamboo curtains, shade nets, and shacks, it is sealed at 8am every day and uncovered at 5pm. When the temperature is too high, water can be sprayed on the bamboo curtain or the shade net. Seedlings should be loosened, weeded, and spawned 1 to 2 times.
Fifth, appropriate dense planting. Strengthen fertilizer management 25 to 30 days of seedling age, colonization when 4 to 5 true leaves. The seedling age is too long and it is easy to cause bolting before being cooked. Autumn lettuce growth is fast, growth period is short, can be properly planted. General plant spacing 20 to 28 cm square. After planting, water should be diligently applied and quick nitrogen fertilizer should be applied immediately after living. Then waterless, shallow cultivator, and promote root development. After the group was planted, the topdressing was performed for the second time. The quick-acting nitrogen fertilizer was mainly used as the potash fertilizer. When the stem begins to swell, the top dressing is applied for the third time, and nitrogen and potassium fertilizers are used together. Stop dressing topdressing about 15 days before harvest. In the expansion period of bamboo shoots, 500ppm to 800ppm of Qinggansu or 350ppm of CMC can be sprayed to prevent the shoots from bolting and increase the yield and quality of lettuce.
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