Cultivation techniques of lettuce

Lettuce, also known as leaf lettuce, belongs to Compositae, lettuce genus, is a 2012 herbaceous crop, originated in the Mediterranean coast, introduced into China in about the 5th century, mainly cultivated in South China. Lettuce is rich in vitamins and minerals. In the process of cultivation, customers are easy to get pollution-free products without pesticides, which are more and more welcomed by consumers, and the planting area is increasing year by year. The following briefly introduces the cultivation techniques of lettuce.

I. preparation of bed soil

Nursery seedlings can be planted in the field. The nursery bed soil is 50% garden soil and 50% rotten soil, and 50 grams of urea and 500 grams of superphosphate are added to each cubic meter of bed soil. After mixing and sieving, the seedbed soil is 5 cm thick (when dividing seedlings, the seedbed soil is 10 cm thick).

2. Raising seedlings

The main results are as follows: 1. Seed treatment: the spring cultivation is generally from February to April, and the seedlings are sowed directly and sowed in summer and autumn from June to August. When the weather is difficult to germinate, the seeds need to be soaked and sowed under the condition of 15 ℃ ~ 22 ℃.

2. Sowing: before sowing, the seedling bed is watered with sufficient bottom water, and after the water seeps down, sprinkle 0.5 cm thick fine soil, and then sow seeds. Generally, the seeding amount per square meter of seedling bed is 10 grams, and after sowing, the fine fluvo-aquic soil is 1 cm thick, covered with plastic film to moisturize, and 3-5 days after emergence, the plastic film is removed. Summer and autumn seedlings pay attention to rain protection and sunshade cooling. The nursery bed temperature was controlled at 18 ℃ ~ 20 ℃, and the seedling growth was disadvantageous when the night temperature exceeded 15 ℃. When the seedlings grow a true leaf, the seedlings can be divided according to the row spacing of 6 cm and 8 cm, and the thickness of the seedling bed soil is 10 cm. During the whole seedling stage, high temperature should be prevented from causing slender tall seedlings and ossified seedlings with small leaves and short Hypocotyl formed under drought conditions.

III. Colonization

Lettuce is a shallow root system, which relies on fibrous roots to absorb nutrients, which requires good soil permeability. Before planting, fertilize the soil first, apply 5000 kg of rotten high-quality soil fertilizer and 20 kg of compound fertilizer per mu, plough 15-20 cm after general application, and then make a 1-meter-wide high border with a height of 10-15 cm. In order to increase the ground temperature in winter and spring, plastic mulching and baking land was 15 days ahead of schedule, and the seedlings could be transferred and planted when the local temperature was stable at 8 ℃.

When planting, long-leaf lettuce can be appropriately denser, the row spacing is 20-25 cm, and the row-plant spacing of heading lettuce is 30-40 cm. Planting with dirt. The planting depth should be flat between the ground block and the ground plane. Pour water in time after planting to slow down the seedlings quickly. Generally, 6 days after planting, the seedlings can be delayed to survive.

IV. Field management

After slowing down the seedlings, they can be fertilized and watered. Heading lettuce can be properly squatted for 5-7 days, and then topdressing watering, 10 kg of urea per mu, topdressing with water to keep the soil moist. In addition, 0.2% urea and 0.2% potassium dihydrogen phosphate should be sprayed on the leaf surface of lettuce in the early stage of inner roll of heart leaf.

Lettuce is not resistant to high temperature and humidity. When the temperature exceeds 25 ℃, ventilation and shading measures should be taken. At the same time, lettuce is afraid of waterlogging, so there is no water in the border, and it can be drained in time after rain. After the hot summer rain, it must be watered with cold water in time.

In the middle and later stages of lettuce growth, in order to keep rosette leaves and globular leaves clasping and grow rapidly, it is necessary to provide continuous and uniform water supply so as not to cause leaf ball cracking or bulb opening and growth. Potassium deficient plots, pay attention to topdressing potash fertilizer in this period. Stop watering 5 days before harvest.

5. Timely harvest

The leaves are fully grown, the leaves are green and thick and crisp, and the harvest yield and commodity value are high at this time. If the heading lettuce presses the leaf ball hard, it has a certain bearing capacity, and the leaf ball is harvested when the tightness is moderate. The method of harvesting is: long-leaf lettuce, large leaves can be picked and leaves can be left, and the picked leaves can be put on the market and the whole plant can be cut off. When the heading lettuce is harvested, it is cut from the ground, the outer old leaves are removed, and 3 or 4 outer leaves are retained outside the leaf bulb to be packaged and listed on the market.

VI. Pest control

1. Downy mildew

① symptom: damage to leaves. The diseased leaves have yellowish disease spots, white mildew on the back of the leaves when it is wet, continuous disease spots in the later stage, and yellowish brown dry leaves when dry.

The transmission route and pathogenic conditions of ②: fungal diseases, seeds and diseased plant residues can carry bacteria, and bacteria can be transmitted by wind and rain. Bacteria can invade the plant directly through the epidermis or stomata. When the temperature is 15 ℃ ~ 20 ℃, it is wet and overcast and there are water layers or water droplets on the surface of the plant.