1, seed selection. Choose loose leaf or ball lettuce seeds, such as French butter lettuce, American fast lettuce, glass lettuce, emerald lettuce, purple leaf lettuce, Italian lettuce and so on.

2, soaking seeds to accelerate germination. Soak the raw rapeseed in cold water for 4-6 hours, then wash the seeds out, wrap them with wet gauze with good air permeability, and put them in the environment of 15- 18℃ to moisturize and accelerate germination. In the absence of a constant temperature environment, they are usually kept in the refrigerator for moisturizing, or wet gauze is hung above the water surface in the well to ensure that the seeds will not be soaked in water, and then placed in a cool place for 24 hours to continue moisturizing and accelerate germination until the seeds are exposed.

3. Prepare the seedbed. Seedlings are raised with ready-made seedling substrates, seeds that accelerate germination and expose white are evenly spread on the seedling tray, and the sowing amount per square is controlled at 3-5g, and the reserved substrates or fine sand are evenly and thinly covered on the upper layer. Irrigation with nutrient solution with PH value of 6.0-6.9 at 8-9 am every two days, 4-6 days in early spring and 3-5 days in summer and autumn with suitable temperature, the seedlings can grow completely. Lettuce grows very fast, with an average seedling period of 8 spans in greenhouse 15-20 days.

4. Seedling planting. When the seedlings grow two true leaves, they can be packaged in time. Rock wool or other media suitable for packaging seedlings is generally used (in order to fix seedlings). Seedling wrapping steps: seedling raising → root washing → root wrapping → placing in a hole tray for maintenance → planting. The planting eyes of the foam board in the planting tank are 20cm*20cm, and the diameter of each eye is about 2.5cm. When planting, put the seedlings wrapped with rock wool into the planting cup, and then put them into the eyes of the foam board.

5. Growth management. Because the growth period of lettuce is short, the nutrient solution generally does not need to be replaced. A prepared nutrient solution can be circulated 2-4 times a day, but not at night. When the root system is underdeveloped, the water level is higher and should reach the root. When the plant is slightly larger and the root system is developed, the water level of nutrient solution should be lowered, and the bottom of the planting cup should be 4-6cm upward, which is beneficial to the root system to absorb oxygen.

Extended data:

1 Main value of lettuce:

1, medicinal value

Lettuce is sweet and cool. Because its stems and leaves contain lettuce, it tastes slightly bitter. It has the effects of clearing away heat, refreshing, relieving pain, hypnotizing, lowering cholesterol, and adjuvant treatment of neurasthenia. Lettuce contains mannitol and other effective ingredients, which has the effects of diuresis and blood circulation, liver-clearing and gallbladder-benefiting.

2. Health care value

Lettuce contains interferon inducer, which can stimulate normal cells to produce interferon, resist virus and improve human immunity. Lettuce contains a substance called protocatechuic acid, which has obvious inhibitory effect on cancer cells, especially in resisting digestive system cancers such as gastric cancer, liver cancer and colorectal cancer.

3. Edible value

Lettuce is rich in nutrients, including a large number of β-carotene, antioxidants, vitamin B 1, B6, vitamin E, vitamin C, a large number of dietary fiber, magnesium, phosphorus, calcium and other trace elements and a small amount of iron, copper and zinc. Strengthen the digestion and absorption of protein and fat, improve the blood circulation of the stomach, and eat lettuce often.

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