Cultivation techniques of lettuce

lettuce growing environment

Lettuce is sensitive to the acidity and alkalinity of the soil and is suitable for growing in slightly acidic soils.

The root system of lettuce is shallow, the absorption capacity is weak, and the oxygen requirement is high. The soil for planting lettuce is sandy loam and loam.

Cultivation techniques of lettuce

1. Variety selection

Winter lettuce, spring lettuce selection cold-resistant, adaptable, late bolting varieties, such as cold-resistant white leaf tip, cold-resistant two white skin, bitter leaves, etc. Summer, autumn lettuce, the selection of heat-resistant early-maturing varieties, such as heat-resistant white leaf tip, bitter leaves, heat-resistant leaves greatly, especially heat-resistant two white, wheat and other vegetables.

2. Determination of sowing date

Spring lettuce, December to March greenhouse seedlings, mid-February to late March open field seedlings. Summer lettuce, open field cultivation from April to mid-May, covered with sunshade net from late May to July, direct seeding or high density planting. Autumn lettuce, July to September covered with shading net sowing, seedling transplanting. Winter lettuce, 10-11 months open seedlings.

3. Cultivate strong seedlings

3.1 Soil preparation:

Select the plot with high dry terrain and good drainage as seedbed, apply decomposed organic fertilizer 4000-5000 kg or compound fertilizer 500 kg per mu as base fertilizer 5-7 days before sowing. Before soil preparation, deep ploughing after application, leveling fine, covered with plastic film waiting for sowing.

3.2 Seed treatment:

Sowing in May-September, due to hot high temperature, seed germination is difficult, low temperature before sowing germination. Soak seeds in cold water for 6-7 hours, then wrap them in wet cloth at 20-25℃ to germinate until 80% of seeds are white. Or soak the seeds in cold water for 1-2 hours, wrap them in wet cloth, place them underground at 30 cm from the water surface, drench them with water for 1-2 times a day, germinate in 3-4 days, or soak the seeds for 24 hours, wrap them in wet cloth, put them in refrigerator or refrigerator, freeze them at-3~-5℃ for 24 hours, and then put them in cool place, germinate in 2-3 days.

3.3 Sowing:

Spring lettuce, greenhouse seedling sowing, first remove the seedling bed film, water sole, wait for water infiltration, seeds mixed in a small amount of fine sand or fine soil mixed evenly after sowing. 25- 30g seeds are sown in 10m2 seedbed. After sowing, cover with soil 0.30-0.50 cm, cover with thin film, cover with sunshade net or straw mat at night for heat preservation. Open field seedling covered with small arch shed. Before seedlings emerge, cover late and early, do not ventilate, and raise bed temperature. After the seedlings emerge, proper ventilation is required to keep the bed temperature at 12-20℃ during the day and 5-8℃ at night. Sunshade net early open late cover, 2-3 true leaves time seedling 1 time, seedling spacing 4-5 cm. 5-6 days before transplanting, strengthen ventilation and seedling tempering.

Summer lettuce is sown on cloudy days. 4-5 Sow wet seed cover film in the middle of the month and withdraw from emergence. From late May to early July, cover the sunshade net with small arch shed or flat shed until emergence or 2 true leaves. Cover with sunshade net to prevent rain washing on rainy days. Sow 5-10 grams in 10 square meters. Thinning seedlings once before 2 true leaves, seedling time once after 4-5 true leaves, seedling spacing 10 cm. Healthy seedlings can also be planted at a high density of about 10 cm in plant spacing. After thinning, fixing and transplanting, decomposed and diluted manure water is applied in combination with watering. In rainy days, ditch cleaning and drainage, irrigation of 0.50% urea water once about 15 days before planting. After 25 days or so, tender plants can be harvested and marketed.

Before sowing autumn lettuce, the bed is watered thoroughly, and after sowing, a layer of decomposed pig manure residue with 3-4 concentration is covered, and a layer of thin straw is covered, or a black sunshade net is covered to sow bud seeds or wet seeds. Before emergence, the double-layer floating surface is covered on the seedbed soil, and after emergence, the silver-gray sunshade net is covered. Watering fertilizer in the morning and evening, keeping the bed soil moist, weeding and thinning seedlings in time.

4. Planting and management

When planting, select loam with good drainage conditions and apply decomposed organic fertilizer 4000-5000 kg per mu. Deep turning and leveling to make high beds 1.20-1.50 meters wide. Water the seedbed before sprouting.

Spring lettuce, seedling age 25-30 days, planting at 5-6 leaves, plant spacing 20 cm ×27 cm, depth to the base of the first petiole is appropriate, watering after planting. Leaves listed, plant spacing 15 cm ×20 cm. Mulched with plastic film, the base fertilizer is applied at one time, and the plastic film is covered, and the rain is drained to prevent stains. Greenhouse and open field cultivation, select sunny warm weather cultivation 1-2 times, timely watering and topdressing, early light manure frequent irrigation, keep the ridge surface moist, when the plants are basically closed ridge, tender plants can be listed. For stem products, 15 kg urea is applied 1-2 times per mu.

Autumn lettuce, seedling age 25 days, planting, plant spacing 25 cm × (30-35) cm, young plants listed, plant spacing 15 cm ×20 cm. Choose cloudy day or afternoon after planting, timely irrigation pressure hill water, and the use of greenhouse, small arch shed or flat shed cover sunshade net, slow seedling withdrawal. Less intertillage, shallow intertillage, light manure frequent irrigation, keep the soil moist, before and after the plant ridge sealing period, apply 3-4 mature human and animal manure 3000-4000 kg or 15 kg urea 2-3 times per mu.

Winter lettuce, seedbed base fertilizer should not be excessive. The seedling age is about 40 days, and the planting is covered with plastic film, and the plant spacing is (30-35) cm × (30-40) cm. After survival, apply 1-2 times of light manure water. If the next year is listed as an adult plant, pay attention to seedling training before overwintering. It is not advisable to fertilize and water too frequently to prevent excessive growth of seedlings. Apply antifreeze fertilizer water again before freezing. Weeds should be cleared in time in the following spring, shallow cultivation should be carried out once, and topdressing concentration should be increased from small to large. After the stem base began to expand, the number of topdressing decreased and the concentration decreased. The use of plastic film and greenhouse cultivation, to apply sufficient base fertilizer, pay attention to ventilation management.

5. Harvest and seed collection

Young plants can be harvested and marketed at any time before the stems are fully plump. When the tip of lettuce is level with the tip of the tallest leaf, it is the right time to harvest lettuce stems. Autumn lettuce in order to extend the market period, delayed harvest, can be used in sunny days with hand pinch to grow points and buds, or rosette stage, spray 350-500 mg/kg chlormequat 2-3 times every 5-7 days, or in the base hypertrophy every 5 days spray 2500 mg/kg green 2 times.

It is better to keep winter lettuce seeds, and isolate about 1000 meters between varieties. Select and keep the plants with strong growth and characteristics of this variety. After thinning, keep the row spacing of plants more than 33 cm square, remove old leaves, apply fertilizer and water, cultivate soil, and promote the growth of lateral branches. When flowering, some branches should be properly removed, pillars should be inserted to prevent lodging, water should not be lacked at flowering stage, irrigation should be reduced after flowering, 20-25 days after flowering, leaves of seed plants should be normally yellow, seeds should be brown or silver-gray, and white crown hair should be harvested in time.