Technical points of planting large lettuce in simple consumer market

Lettuce is the common name of leaf lettuce, belonging to Compositae lettuce genus, is an annual or biennial herbaceous crop; lettuce can be divided into green lettuce and purple lettuce according to the color of leaves. If distinguished according to the growth state of the leaves, there are two kinds of lettuce: loose leaf lettuce and heading lettuce; the former leaves are scattered and the latter leaves clasp into a ball.

Lettuce

1. Planting conditions

1.1.Climatic conditions lettuce likes cool climate, and the lowest temperature of seed germination is 4 ℃, which takes a long time. The optimum temperature for germination was 15-20 ℃. After 3-4 days, the germination was blocked when the germination was over 30 ℃. Therefore, low temperature treatment should be carried out when sowing in summer to promote the activity of enzymes and the transformation of other substances in the seeds. The optimum temperature for stem and leaf growth of heading lettuce is 11-18 ℃, and the optimum temperature for heading stage is 17-18 ℃. The seedlings can tolerate-5 ℃ and low temperature more than 21 ℃, which is not easy to form leaf ball or cause heart leaf necrosis and rot due to high internal temperature of leaf ball. When the temperature is above 30 ℃, the growth is poor. The temperature adaptation range of non-heading lettuce is wider than that of heading lettuce. For the sensitivity to sunlight, the early-maturing variety was the most sensitive, the middle-late-maturing variety was the second, and the late-maturing variety was slow to respond.

1.2. Soil conditions lettuce is suitable for slightly acidic soil, which is planted in soil rich in organic matter, with strong water and fertility conservation and high yield. for example, in the soil of drought and lack of water, the root system is underdeveloped, the growth is not full, the vegetable taste is slightly bitter, and the quality is poor.

1.3. Water conditions different growth periods of lettuce have different requirements for water. Seedling stage can not be dry can not be too wet, too dry seedlings easy to aging, too wet seedlings easy to grow. In the budding stage, the moisture should be properly controlled, the moisture in the heading period should be sufficient, the water deficiency leaves are small, and the taste is bitter. Do not have too much water in the late stage of heading, so as not to crack the ball and lead to disease.

2. Cultivation techniques.

2.1. Selecting varieties of lettuce and selecting suitable varieties, combined with protected cultivation, can achieve annual production and annual supply. The non-heading varieties with strong resistance are mostly used in early spring, because the heading varieties are easy to bolt in early spring and are not easy to heading in summer high temperature season.

2.2, sowing and Seedling sowing period of lettuce in Beijing-Tianjin area: sowing and raising seedlings in spring from February to April, harvesting from May to June, sowing and raising seedlings in autumn from late July to late August, and harvest from October to November. Annual production and supply can be achieved by using protective facilities, and non-heading varieties with strong resistance should be adopted for early sowing, otherwise heading varieties are easy to bolt in early spring and not easy to heading in summer high temperature season. After sowing, it can germinate in 3-4 days under the condition of suitable temperature of 15-20 ℃. Because the seed price of lettuce is expensive, the method of raising seedlings and transplanting is generally adopted in production. The general seed consumption of seedling bed is 0.75-1.5 kg per mu, suitable sparse sowing to cultivate strong seedlings. One mu of seedbed can plant 10 mu of land. Generally, seed treatment should be carried out when lettuce is sown and raised seedlings in autumn. First soak the seeds for 12 hours, then rinse them with clean water, wrap them with wet gauze, treat them in a low temperature of 5-6 ℃ for 2 days, and then take out and sow most of the seeds when they begin to whiten. After sowing, the soil cover should not be too thick, generally about 0.5-1 cm. It is hot and rainy in summer and autumn, so shade should be covered with shading net after sowing.

2.3. The root system of lettuce is not deep, so we should choose the soil with strong water conservation, fertility and fertile soil. General planting density: the row-plant spacing of early-maturing varieties is 23 cm × 20 cm, and that of middle and late-maturing varieties is 33 cm × 24 cm. Lettuce is generally fertilized 3-4 times. Slow seedling fertilizer should be applied once after planting slow seedling, the fertilization concentration should be dilute, and the overwintering spring lettuce should be topdressing once after planting, but generally not fertilized in winter. It needs to be topdressing for 2-3 times in spring.

2.4. The main diseases of lettuce include downy mildew, soft rot, virus disease and Sclerotinia sclerotiorum. Sclerotinia sclerotiorum and soft rot are more harmful and are easy to occur under warm and humid conditions. Take rotation, reduce planting density, not too much watering, often shallow hoe, to keep the soil surface dry. Often clean the field, find diseased plants and pull out in time. Remove dead leaves and concentrate on burning. Agricultural streptomycin and desenamine can be sprayed after the disease. Spray chlorothalonil every 5-7 days in the season of high temperature and humidity for the purpose of prevention. Insect pests are mainly aphids, thrips, ground tigers, etc., with omethoate, quick kill and other control.

2.5. Lettuce should be harvested in time after maturity, and the quality will be affected a little later. Loose-leaf lettuce can be harvested about 40 days after planting, with a single plant weight of 0.2-0.4 kg, and heading lettuce can be harvested 50 days after planting, weighing 0.4-0.5 kg per plant. Yield per mu: 1000-1500 kg for early-maturing varieties and about 2500 kg per mu for mid-late maturing varieties.