The key technology of lettuce cultivation in early spring cold sheds in Tianjin area
Wu Wenzhong
Lettuce is a common vegetable in daily life, crisp and refreshing, and rich in nutrients. In addition to vitamins and minerals, lettuce also contains iron elements that are beneficial to the body's absorption, as well as rich in phosphorus and calcium. Lettuce is low in sugar and contains niacin, which is regarded as an activator of insulin in the human body, and is one of the most popular vegetables. Lettuce has strong adaptability, likes cold and is afraid of high temperature, and is suitable for planting in spring and autumn. The author summarizes the planting technology of lettuce in early spring cold sheds in Tianjin for the reference of growers.
1 Soil selection
Lettuce is highly adaptable to the soil, but to achieve the purpose of high yield, it is necessary to choose a loose, fertile and irrigatable loamy land.
2 Variety selection
There are many varieties of lettuce, which can be divided into pointed lettuce and roundleaf lettuce from the leaf shape. At present, the production of upper-tip leaf lettuce varieties in Tianjin is generally late-ripening, with long internodes and heat-tolerant seedling stages. Garden leaf lettuce is precocious, hardy and heat-resistant, with higher yields, good quality, and easier to be accepted by consumers. When planting, you can choose the green skin and green meat garden leaf varieties that are not easy to smoke, disease resistance and high yield, and you can also choose the planting varieties according to the consumption habits of consumers.
3 Germination and seedlings
3.1 Soaking seeds to germinate
Lettuce is a cool crop, not tolerant to high temperatures, the minimum temperature of seed germination is 4 °C, the suitable temperature is 15 ~ 20 °C, more than 30 °C is hindered by germination. Pre-sowing soaking seed germination is conducive to seedling emergence, generally using the refrigerator germination method, the seeds are soaked in water for 12 to 24 hours after fishing out, put into a small cloth bag, put into the refrigerator preservation layer of 5 °C environment to germinate. Remove the seeds every 12 h and rinse them with water, after 3 to 4 days, when 80% of the seeds are sprouted, they can be sown.
3.2 Seedbed nursery
Lettuce can be sown and raised around the beginning of January every year, and a flat seedbed is made in a cold shed, with a furrow width of 1 m and a furrow stem height of 20 cm, and the length depends on the planting habits. Level the soil in the fine furrow, mix a small amount of fine sand after the seeds sprout and sow evenly, the sowing density is 2 ~ 3 g·m-2, the sowing amount per 66.7 m2 seedling land is 100 ~ 150 g, and the seedlings can be planted 1 334 m2. Cover the soil in time after sowing, and the soil cover should be uniform, 1.5 cm thick, to prevent the seeds from exposing, and also to avoid the thick soil covering affecting the emergence of seedlings. After the completion of the soil covering, the foot pedal shock pressure is used to maintain soil moisture and facilitate the emergence of seedlings. After sowing, the mulch is covered, and then a small arch is set up on the furrow surface.
After sowing, the seedlings can emerge 10 to 12 d, the cotyledons are expanded and the mulch film is removed, and then the seedlings are between the seedlings 2 to 3 times, and the weeds are manually pulled out, and the plant spacing is 3 cm after the seedlings are fixed. 7 to 10 days before colonization, the small arch shed is removed and the seedlings are refined. 7 days before transplantation, apply "sending fertilizer", apply urea 5 ~ 10 kg per 667 m2, and water 1 d before transplanting seedlings to alleviate the degree of root injury of seedlings. Large and small seedlings are colonized separately to facilitate cultivation field management. At the seedling stage, attention is paid to the control of underground pests and snails.
4 Prepare the land for furrow before colonization
Lettuce cultivation base fertilizer should be sufficient. It can be combined with land preparation, and 2 500 kg of fully decomposed farmhouse fertilizer and 40 kg of urea are applied per 667 m2. After the fertilizer is evenly applied to the soil, ploughing and spinning rakes are carried out to make the soil flat, fine, loose and breathable. After turning, it is flat and the width of the furrow is 2 m.
5 Colonization and post-colonization management
5.1 Colonization
Cold shed cultivation is settled in mid-March. Seedlings are suitable for seedling age of 4 leaves and 1 heart, when transplanting seedlings, the seedbed should first be watered through the bottom water to prevent excessive damage to the roots and affect the survival rate and slow seedlings after colonization, choose cloudy days or afternoon soil transplanting, each seedling is best to bring more than 50 g of soil blocks. Each furrow is colonized in 6 rows with a row spacing of 40 cm and a plant spacing of about 30 cm. When planting, separate the large and small seedlings, grasp the surface of the seedling soil block and the furrow surface, and should not be planted too deeply. Water the colonization water thoroughly, water the seedlings in time, and promote the survival of the seedlings as soon as possible.
5.2 Weeding in medium tillage
After colonization, medium tillage 1 to 2 times. Pay attention to the timely removal of weeds from the field.
5.3 Topdressing and watering
The lettuce furrow surface cultivated in the early spring shed should not be too large, and can be irrigated. Lettuce must look at the seedling topdressing, seedling growth is poor plot, can be applied urea 15 kg ·667 m-2 in the early stage of growth, the whole growth period combined with watering to chase compound fertilizer 1 to 2 times; pay attention to timely watering, keep the soil moist, watering should choose to be carried out in the evening or early morning. In order to replenish nutrients, it is necessary to pay attention to foliar topdressing, which can be sprayed together with anti-pest drugs, spraying 600 times tianda + 0.3% urea once every 7 to 10 days, spraying 2 to 3 times continuously, and spraying 0.3% potassium dihydrogen phosphate 1 to 2 times at intervals.
5.4 Temperature and humidity management
The suitable growth temperature of lettuce is 15 to 20 °C during the day and 10 to 15 °C at night. If the temperature management of the shed is improper, it is very easy to cause low temperature to smoke moss in advance and high temperature plants to grow. When the plant enters the expansion stage of the stem, the air outlet should be opened in a timely manner according to the growth of the plant, and the ventilation should be increased; if the plant is growing too strongly, a spray of chlorpyrifosin 350~500 mg·kg-1 can be used to promote the hypertrophy of the stem and increase the weight of the stem.
5.5 Pest control
In the case of improper temperature and humidity control, lettuce is prone to disease. Lettuce mainly includes downy mildew, gray mold, aphids and spotted fly. High temperature and high humidity are prone to downy mildew disease, the initial stage of the disease can be used 66.8% mold Dogg wettable powder 1 000 to 1 500 times liquid, or 77.2% downy mildew water agent 1 000 ~ 1 700 times liquid foliar spray control. Low temperature and high humidity are easy to cause sclerotia, which can be prevented and treated with 50% parahynthene wettable powder 1 500 to 2 000 times liquid, or 50% soxchre wettable powder 2 000 to 2 500 times liquid. Aphids and spotted flies can be controlled with 2% avermectin 3,000 times, or 75% fly-killing amine 7,500 times, or 20% acetamiprid 8,000 to 10,000 times liquid. Note that the use of pesticides is prohibited within 10 days before harvesting.
6 Timely harvesting
Lettuce from colonization to harvest takes about 55 d, when the top of the main stem of the lettuce and the tip of the highest leaf can be harvested at the same time, the harvest period of lettuce is also the most rapid period of moss extraction, if not harvested in time, lettuce is very easy to smoke moss, after the moss product becomes hard, or even hollow.