What are the scientific methods for growing lettuce?
How do you grow lettuce scientifically? Please give a detailed introduction to the growing methods. Lettuce can be grown by referring to the following methods: 1. Soil selection: choose fertile, slightly acidic soil rich in organic matter, with strong water and nutrient retention, good aeration, and convenient drainage and irrigation. 2. Variety selection: for growing lettuce, varieties such as glass lettuce, crisphead lettuce, curly-leaf lettuce and Caesar are better.
How do you grow lettuce scientifically? Please give a detailed introduction to the growing methods.
Lettuce can be grown by referring to the following methods:
1. Soil selection
Choose fertile, slightly acidic soil rich in organic matter, with strong water and nutrient retention, good aeration, and convenient drainage and irrigation.
2. Variety selection
For growing lettuce, varieties such as glass lettuce, crisphead lettuce, curly-leaf lettuce and Caesar are better.
3. Sowing and raising seedlings
The sowing period is generally from August to February of the following year, but the most suitable sowing period is from late October to mid-December. Sowing can also be done from early March to early May, but the growth period is short and the yield is low. In winter and early spring, grow in large or small plastic tunnels; in summer, grow under shade netting or in a shaded shed. For the seedling bed, apply 1500 kg of decomposed farmyard manure and 20 kg of superphosphate per 667 sq m, then plow and mix evenly and level. Glass lettuce is best sown from September to January of the following year, and crisphead lettuce from October to December. For raising seedlings and transplanting, each 667 sq m of growing field requires 20-30 sq m of seedling bed and 25-30 g of seed.
When sowing in the high-temperature season, the seeds must be subjected to low-temperature germination stimulation. The method is: first soak in well water for about 6 h (hours), rub and wash, then take them out and wrap them in moist gauze, and place them at 15°C-18°C to germinate, or hang them in a water well to germinate, or put them in a refrigerator (temperature controlled at about 5°C), and after 24 h (hours) place the seeds in a cool place and keep them warm to germinate. A 2‰ "920" solution can also be used to soak the seeds for 24 h (hours), which can smoothly break the dormancy of lettuce seeds, and germination will be complete in 2-3 d (days); when 80% of the seeds have sprouted, sow them promptly.
Before sowing, water the seedling bed thoroughly, mix the seeds evenly with an equal amount of moist fine sand, and broadcast them, covering with soil about 0.5 cm thick. When there are 2-3 true leaves, thin or transplant the seedlings promptly. For seedling raising in large tunnels or open fields in winter and spring, pay attention to keeping the seedling bed warm, and at the same time control the amount of watering to prevent excessive humidity; for open-field seedling raising in summer, pay attention to covering with shade netting, water 2-3 times a day, and keep the soil moist.
4. Transplanting
Glass lettuce seedlings are about 25 d (days) old and can be transplanted when they have 4-6 true leaves, with a plant and row spacing of 14 cm × 18 cm. "Crisphead lettuce" seedlings are 30-35 d (days) old and are transplanted when they have 5-6 true leaves, with a plant and row spacing of 17 cm × 20 cm, and a bed width of 0.8 m-0.9 m. Apply 4000-5000 kg of organic fertilizer and 20 kg of superphosphate or 50 kg of compound fertilizer per 667 sq m of transplanting field. When transplanting, keep soil around the roots and water promptly to settle the roots. The planting depth should be such that the heart leaves are not buried. If transplanting in the high-temperature season, build the frame on the morning of the transplanting day, cover with shade netting, and transplant after 4 p.m. For winter and spring cultivation, plastic film mulching can be used. For transplanting in large tunnels, the daytime temperature should be controlled at 12°C-22°C as suitable; if the temperature is too low, pay attention to keeping warm; when the temperature is above 24°C, remove the film for ventilation and cooling. Under normal circumstances, the skirt film of the large tunnel can be left open.
5. Field management
Lettuce needs a lot of fertilizer, so apply fertilizer frequently and in larger amounts. 5-6 d (days) after transplanting, apply a small amount of quick-acting nitrogen fertilizer; after 15-20 d (days), apply 15-20 kg of compound fertilizer per 667 sq m; after 25-30 d (days), apply 10-15 kg of compound fertilizer, but human excrement and urine must not be used as a top dressing in the middle and late stages. After transplanting, the water requirement is high. According to the weather after seedling recovery and the soil moisture conditions, water at the right time, generally once every 5-7 d (days); watering in the middle and late stages must not be excessive.
6. Pest and disease control
Aphid damage mostly occurs in autumn, winter and spring, and can be controlled by spraying 600-800 times dilution of 40% dimethoate emulsifiable concentrate, or 2000-3000 times dilution of 50% pirimicarb, etc. Sclerotinia disease mostly occurs in February and March, and can be controlled by spraying 500-700 times dilution of 70% thiophanate-methyl wettable powder or 1000-1500 times dilution of 50% iprodione powder. Soft rot is prone to occur in hot and rainy seasons, and can be controlled by spraying 1000 times dilution of 47% kasugamycin-copper wettable powder, or 500 times dilution of 77% copper hydroxide wettable powder; stop applying the pesticide 15 d (days) before harvest.
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