High-yield cultivation technology of winter lettuce in greenhouse

As the main vegetable variety in Zhoushan, Lettuce has achieved annual cultivation. In the past, due to the reasons of facilities, the cultivation area of ​​winter lettuce was relatively small. With the rapid development of steel greenhouses in Zhoushan in recent years, the area of ​​winter lettuce cultivation has increased. Compared with other cultivated vegetables, winter lettuce is more convenient to manage and its economic benefits are more obvious. It has become a large variety of winter and spring vegetables. However, in the production process, there are problems such as poor quality and poor commerciality due to improper selection of varieties, lagging disease control technology, and abuse of chemical fertilizers. After years of research and promotion, the author has concluded a set of technologies suitable for local and northern Zhejiang planting. The key technologies are as follows:

1. Land selection

The root system has a weak absorption capacity and high requirements for oxygen, and it is prone to downy mildew and sclerotinia when the humidity is high. Therefore, it is required to plant on cohesive loam or sandy loam with high terrain, convenient drainage and irrigation, rich organic fertilizer content, and strong water and fertilizer retention capacity.

2. Variety selection

Middle-late maturity varieties must be selected for planting winter lettuce, and early maturing varieties are prone to bolting. In recent years, two varieties such as Sanqingpi of Fujian and Jinming No.1 of Fujian have performed well in the local area. Sanqingpi is an excellent variety in Jiaxing City of the province. It has a plant height of 40 to 45 cm, long oval leaves, dark green leaves, wrinkled leaves, 30 cm long leaves, thick fleshy stems, green skin, and green flesh. The first harvest is about 80 days. Jinming No.1 is a new variety introduced in recent years. It has strong resistance to sclerotinia sclerotiorum in fields that have been planted with lettuce for several years. Its main characteristics are: plant height of about 50 cm, shallow and dense roots, tip of leaves, wrinkled leaves, green-purple leaves, erect stems, lavender, strong aroma, thin skin, and emerald green, sowing to first harvest About 90 days.

3. Seeding

3.1 Sowing date selection. The sowing date of local winter lettuce is determined to be mid-September, and the average daily temperature is preferably lower than 23 ° C.

3.2 Sowing. When planting in mid-September, because the air temperature and soil temperature were relatively high at that time, the seeds needed to be treated. First, wrap the seeds with gauze and soak them in well water for 5-6 hours, and then place them in the refrigerator freezer for germination treatment for 48 hours. Suitable temperature for sowing and germination is 15 ℃ ～ 20 ℃. The planting density should be low, and the seed amount per mu is about 15 grams. The seedling-to-book ratio is 1: 6. Generally, the 6 meters × 30 meters grams of P622 steel greenhouse promoted locally is sown by 30 grams, and 6 sheds are planted. The seedbed can choose a vegetable garden with high fertility, and then apply 15 kg of superphosphate per acre, plow the soil, pour water, cover with 1 to 2 mm of fine sand and plant it.

3.3 Seedling management

After sowing, the topsoil can be lightly covered with a rake without covering the soil. After covering the shading net for 2 to 3 days, the temperature of the seedbed can be maintained at 20 ° C to 25 ° C. When the cotyledons of the young seedlings are enlarged, they can be removed. After emergence, the temperature during the day is controlled from 18 ° C to 20 ° C and at night from 8 ° C to 10 ° C. At the seedling stage, spray 5% ank 2500 times solution, 75% chlorothalonil 800 times solution and other pesticides to spray the disease 2 to 3 times to control the disease, and carry out artificial weeding. Fertilization is generally not applied at the seedling stage, which makes the leaf color of the seedlings lighter, which is conducive to slow seedlings after transplanting.

4. Field management

4.1 The planting age of winter lettuce is controlled at about 20 days, and it can be planted when there are 3 to 4 true leaves. The row spacing of the plants is 30 cm × 40 cm (that is, 6-meter-wide sheds are planted in 3 centimeters, with 5 rows per species).

4.2 Fertilizer and water management Winter lettuce requires sufficient fertilizer and water, generally 3,000 kg per mu of rotten cooked pig manure and 50 kg of 24% compound fertilizer. Before the planting, the field was fully absorbed, and after 2 days of infiltration, the tiller was planted in time. The topdressing is combined with watering and foliar spraying. It is used 500 times potassium dihydrogen phosphate solution when the leaves are in a rosette shape 15 days after planting, and 1000 times liquids such as Green Fenway No. 2 and No. 3 during the fleshy stem growth period. Foliar spraying was applied outside the root. In the initial stage of the rosette, every 6m × 30m standard shed was poured with 1kg of urea plus 1kg of nitrogen, phosphorus, and potassium all with 16% compound fertilizer on 500kg of water, and every 6m × 30m standard shed before being sealed. 500 kg of water was poured with 2 kg of urea plus 2 kg of nitrogen, phosphorus, and potassium, all of which were 16% compound fertilizer. Winter lettuce is very prone to sclerotinia if the humidity is high in the field after being covered with plastic. Therefore, it is necessary to pour water in small quantities to keep it moist and not accumulate water.

4.3 Plastic film management The film management of local winter lettuce is mainly ventilation. The film coating time is generally in mid-November, the first 2 to 3 days of the initial frost period. The temperature difference can be increased during the rosette period. Except for the closed film insulation on frosty days, the skirt film and the door are ventilated for the rest of the time, and the stems and leaves grow. * The suitable temperature is 10 ℃ ～ 19 ℃. The succulent stalks began to be insulated with closed membranes at the early stage of formation. When the temperature reached above 18 ° C during the day, ventilation was performed to reduce the temperature and humidity to prevent the succulent stalks from rising too fast and prevent sclerotinia.

4.4 Pest and disease control Local winter lettuce has fewer pests, mainly aphids, which can be trapped with yellow boards. For pesticide control, spray 20% nanbao (Acetamiprid) soluble powder 5000 times for whole plant spraying. Disease is the most important factor that causes the local winter lettuce not to be highly commercialized. It mainly includes sclerotinia, downy mildew, and viral diseases. Sclerotinia sclerotiorum is a serious disease endangered by local winter lettuce, which causes rotting of succulent stems. Improper control will result in unsuccessful harvest. The disease should be mainly controlled by agriculture, be timely ventilated, reduce the humidity in the shed as much as possible, strengthen plant fertilizer and water management, and enhance the disease resistance of plants by spraying foliar fertilizers rich in trace elements. The pesticide can be sprayed with 90% of Shijiale 1000 times liquid and 40% of sclerotia sclerotia 600 times liquid at the early stage of disease. Downy mildew is also an important disease of local winter lettuce, which mainly harms the leaves of plants. In the early stage of the disease, it can be sprayed with 72% DuPont Cloth 600 times solution and 50% Anker 1500 times solution. According to the author's observations for many years, it is believed that the occurrence of winter lettuce virus disease has a great relationship with the temperature. In the case of frequent changes in hot and cold air, the symptoms of plant virus disease are obvious. Therefore, in this climate environment, it is necessary to strengthen the shed film. Cover management, so that the temperature difference in the shed does not change much, and it is necessary to prevent aphids in time.

5. Economic benefits

Winter lettuce is cultivated in a greenhouse, so that lettuce can be supplied throughout the year, especially when the market period of winter lettuce is around the Spring Festival, and the price is relatively high. This cultivation method has an average yield of about 1500 kg per 6 m × 30 m g P622 shed in the local area. In addition, the winter lettuce can be planted in the shed for a short period of time and is more convenient to operate than the eggplant fruit vegetables. Spring vegetables can be planted in time after harvesting, which has great promotion value.

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