Variety selection Choose cold-resistant, disease-resistant and adaptable varieties such as the emperor, Salinas, and Great Lakes 659. The nursery should choose fertile sandy loam with strong water retention and fertility.
Seedling preparation is due to the small size of lettuce seeds, strict requirements for seedbed cultivation, fine soil preparation, and careful crushing and leveling of bed and soil. 10 kg of farmhouse manure, 10 kg of diammonium phosphate, and 0.3 kg of potassium dihydrogen phosphate were thoroughly crushed and used per 10 m2 of seedbed. Spread the ground evenly, plowing 10-12 cm, plowing and plowing and leveling and practising.
Seed treatment Lettuce seeds can be sown, but also germination. When seeds are sown, they should be seeded with 75% chlorothalonil wettable powder equivalent to 0.3% of the dry weight of the seeds before sowing. Immediately after sowing, seeds should be sown overnight.
When soaking germination, first soak seeds in water at about 20°C for 3 to 4 hours. After washing, drain the water, put it in a wet gauze bag or pot, and germinate at 20°C. Rinse with water once a day. After germination, germination will continue. Buds can be budded in 2 to 3 days. When the temperature is too high under natural conditions, the germination can be placed on the wellbore or in a cave, etc. The temperature is controlled at 15°C to 20°C.
Sowing: Before seeding, the seedbed is poured into the bottom water. When the drowning water does not seep through, the sieved soil is leveled. After the water is infiltrated, 0.1–0.2 cm fine soil is sieved and then sown. Use 375-450 grams per hectare. In order to nurture strong seedlings and prevent seedlings from becoming leggy and forming tall or weak seedlings, sowing should not be too dense. It is generally advisable to broadcast 1 gram per square meter of seedbed. For uniform seeding, the seeds can be mixed and spread in 2 separate shots, and the sieved soil is then covered with 0.3-0.5 cm. To prevent the loss of water, straw, wheat straw, or mulch can be applied to the surface according to the ground temperature. In order to prevent ants, cockroaches, etc. from eating seeds, sow dimethoate and dichlorvos on the bed after sowing.
Seedling management generally keeps the bed temperature at 20°C～25°C after sowing, and the glutinous surface is moist, and 3～5 days can be seedlings. If the temperature is too high, it should be shaded properly to create a cold and moist environment for the seedlings to grow robustly. When the seedlings have just been excavated, the coverings on the surface shall be promptly removed to prevent the formation of tall plantlets with excessively elongated embryonic axes.
After emergence, 18 °C ~ 20 °C, 8 °C ~ 10 °C at night. After emergence, 7 to 10 days, when the young seedlings have a two-leaf heart, they should be divided in time and the seedlings should be 3 to 5 cm apart. After seedling, it should be sprayed with 500 times potassium dihydrogen phosphate solution or watered with water. At the seedling stage, it is necessary to spray 1 to 2 times of 75% chlorothalonil WP or 70% thiophanate-methyl wettable powder 600 to 800 times to control seedling diseases. The seedling age is 25 to 35 days, and it can be planted when there are 4 to 5 true leaves.
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