Cultivation techniques of head lettuce

1. Selection of the sowing period. Lettuce likes low humidity and cool environment. The autumn cultivation and sowing period is from late September to mid-November. Seedlings can also be grown in protected areas in early spring, and planted from late April to mid-May.

2. Sowing and raising seedlings, soak the seeds for a few minutes and then wrap them in a damp cloth, pay attention to ventilation, and place them in an environment of 15-20℃ to accelerate germination. After 2-3 days of germination, the seeds can be sowed. The nutrient cup seedling method uses a small amount of seed, high seedling survival rate, strong seedlings, and keeps the root system intact when planting, and grows fast after planting, and the heart is early. The formula of nutrient cup seedling soil is 6 parts of soil, 3 parts of compost, 1 part of chaff (or vermiculite), and add a small amount of borax, mix well and put into the cup. Sow 2-3 seeds per cup. After sowing, cover a thin layer of soil, then cover with straw, and pour enough water. In addition, some areas use plugs to raise seedlings, and the effect of seedling formation is also very good.

3. Seedling stage management 2-3 days after sowing, the straw can be peeled off when the buds emerge, and tall seedlings are easy to produce if the grass is not removed in time. For planting and raising seedlings in summer, shelters must be built to prevent rain and provide shade. After emergence, spray water every morning and evening. About 2 weeks after sowing, thin seedlings are carried out, weak seedlings and tall seedlings are removed, and a strong seedling is retained. Thin urea can be applied after 15 days of seedling age. The general seedling period is 25-30 days.

4. Before planting and planting, apply sufficient base fertilizer to make the soil loose so as to facilitate the growth of roots and the absorption of fertilizer and water by roots. Early-maturing species are planted in double rows, with a row spacing of 35 cm, plant spacing of 25-30 cm, and 4000-5000 acres. The mid- and late-maturing species are properly sparsely planted for full growth. High-border cultivation can be used, the row spacing is 40 cm, the plant spacing is 30-35 cm, and 3000-3700 acres are planted. 3-4 days after planting, appropriate watering every morning and evening to increase survival rate. If missing plants are found, replenish seedlings in time.

5. Field management The heading lettuce has a long growth period, so it needs to be topdressed several times, usually once every 7-10 days. Thinly apply quick-acting nitrogen fertilizer 4-6 days after planting to promote root and leaf growth. When starting to pack the core, increase the application of potassium fertilizer. Before the plants are closed, apply heavy fertilizer. Use 20 kg of compound fertilizer and 7.5 kg of potassium chloride per mu. It can be applied in a shallow trench between the two rows, and then covered with soil to prevent the fertilizer from contacting the root system. It can be irrigated or irrigated to keep the soil moist until the beginning of the core (rose stage). In the rosette stage, water must be strictly controlled to avoid diseases. Do not use water spraying or sprinkler irrigation during the heading period. Water spraying or sprinkling irrigation can be used instead of "horse racing" furrow irrigation or watering between rows. Water control should be carried out 15 days before harvest. The root system of heading lettuce is shallow. Intertillage should not be too deep to avoid damage to the root system. Intertillage should be carried out before the plants are closed. When cultivating head lettuce on a large area in Japan, the black mulch method is adopted, which has a good effect on cooling and moisturizing, preventing fertilizer loss and weed production.

6. Harvest head lettuce from planting to harvest, about 55 days for early maturity, 65 days for middle maturity, and 75-85 days for late maturity. But it is better to harvest a few days in advance. The harvest standard can be pressed obliquely from both sides of the leaf ball with both hands, so that the hand feels firm and not loose. Control water 15 days before harvest. When harvesting, select plants with tight leaf bulbs and cut them from the ground, peel off the old leaves, leave 3-4 outer leaves to protect the leaf bulbs, or peel off all outer leaves, use polystyrene film for single-ball packaging, and transfer them in time The refrigerated compartment is shipped out for sale, and the suitable temperature for transportation and storage is 1-5°C.

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