The latest high-yield cultivation technology of lettuce

Lettuce, also known as celery, is widely grown in my country. Its main edible part is its crisp and tender stems, and its tender leaves are also suitable for consumption. Lettuce is a vegetable with excellent adaptability and can withstand cold and long-term storage, making it one of the main vegetables in early spring and autumn and winter. Lettuce can be eaten in a variety of ways. It can be eaten raw or cooked. It can also be used to make processed foods such as kimchi , pickles and dried vegetables . It is very popular among consumers. Let’s learn the latest high-yield cultivation technology for lettuce.

1. Different batches

Open-air cultivation of lettuce is divided into four different cultivation cycles: spring, summer, autumn and winter. This division is mainly determined based on the differences in lettuce sowing time, transplanting time and harvesting time in each season.

Specifically, the sowing period of spring lettuce is from September to October, the transplanting period is from October to late November, and the harvesting period is from January to February of the following year. The sowing period of summer lettuce is from the end of June to the beginning of July, the transplanting period is from July to mid-August, and the harvesting period is from September to October. The sowing period of autumn lettuce is from July to August, the transplanting period is from early August to early September, and the harvesting period is from October to November. The sowing period of winter lettuce is from late September to October, the transplanting period is from late October to mid-November, and the harvesting period lasts from late December to February of the following year.

2. Sowing time

If lettuce sown in spring encounters high temperatures in spring, the growth of leaf clusters and the expansion of stems will slow down, which will not only delay the time to market but also reduce the yield. Therefore, in areas where it is possible to overwinter in the open field, it is recommended to sow spring lettuce in autumn so that the seedlings can grow 4 to 5 leaves before winter and safely survive the cold winter.

After the lettuce sown in autumn resumes growth in the spring of the following year, its root system and leaf clusters can be fully developed under lower temperatures; as the temperature gradually rises, the flower stalks begin to grow and expand rapidly under sufficient nutrition and suitable temperature conditions. The flower stems are already large enough before the high temperature and long day conditions that are favorable for bolting arrive.

However, the time for autumn sowing should not be too late, and early to mid-September is appropriate. If sowing is too late, the seedlings will be susceptible to frost damage due to their small size. At the same time, due to the shortened vegetative growth period, stem expansion is restricted, resulting in late time to market and lower yields. Similarly, sowing should not be done too early, otherwise the seedlings will easily grow excessively under high temperatures, and the plants will be too large before winter, the flower buds will differentiate too early, and they will easily bolt. In addition, if the growth point is exposed, the "shooting up" phenomenon may occur.

3. Spring lettuce cultivation technology

1. Reasonable seedling cultivation

When it comes to growing spring lettuce, soil preparation is key. The soil needs to be deeply plowed and dried to ensure that it is finely broken down and to avoid large clods of soil that could cause the seedlings to freeze and die in winter. In drought or poor soil conditions, the tender stems of lettuce tend to overgrow, so make sure to apply adequate basal fertilizer and make flat beds or high ridges running east-west when preparing the land. Planting lettuce on the south side of the ridge can increase ground temperature, reduce the risk of frost damage, and make the lettuce available to the market 7 to 10 days earlier than flat-bed cultivation.

During the seedling stage of spring lettuce, about 1.5 kilograms of seeds need to be sown per acre of nursery land, and the ratio of the seedbed area to the actual planting area is approximately 1:100. It is recommended to use the wet sowing method and thin out the seedlings in time after emergence, keeping the seedling distance between them at 3 to 4 cm. If the seedlings need to spend the winter in a sunny bed, they should be transplanted when they grow 3 to 4 true leaves, and the distance between seedlings should be kept at about 6 cm. During the seedling stage, water should be controlled moderately to promote thick and flat leaves and prevent excessive growth, which will help cultivate seedlings of appropriate age and strength.

2. Scientific colonization

In the planting of lettuce in spring, for those areas where it can overwinter in the open air, it is recommended to complete the planting work before winter as much as possible. The reason for doing this is that pre-winter planting helps the root system to develop well, allowing for faster growth in the spring, thereby achieving earlier market launch and increasing yields. In areas where safe overwintering is not possible, planting should be done as soon as possible after the soil thaws in early spring. If the planting time is too late, the seedlings are too large or overgrown, it may lead to premature bolting.

When transplanting seedlings, make sure each seedling has a taproot 6 to 7 cm long. If the taproot is kept too short, the fibrous roots will not grow well after planting, which is not conducive to the recovery of the seedlings. If the taproot is too long, the root system may bend in the soil during planting, affecting the growth of new roots and the overall development of the seedling. The spacing between rows and plants during planting is usually maintained at 30 to 40 cm. Generally speaking, the depth of planting in winter should be slightly deeper than that in spring to avoid frost damage. But it cannot be too deep, otherwise it will affect the growth of seedlings. When planting, ensure that the root neck is buried in the soil and compact the soil so that the roots are in close contact with the soil to reduce the risk of frost damage caused by excessive soil gaps.

3. Field management

The field management of lettuce in spring can be roughly divided into three stages: management during the wintering period, management during the greening period, and management during the vigorous growth period.

Management during the wintering period: The focus of management at this stage is to ensure that the lettuce can safely overwinter. When planting in late autumn and early winter, due to the low temperature, planting should be carried out when the soil moisture is suitable to reduce or avoid watering. This can speed up the acclimatization of the seedlings and avoid the seedlings growing too tall due to excessive soil moisture. After the seedlings have grown, quick-acting nitrogen fertilizer should be applied to promote leaf differentiation and expand leaf area. After deep tillage, control watering and do seedling squatting to promote the expansion of the root system and the formation of rosette leaves. During this period, avoid excessive watering before winter to prevent the seedlings from growing too tall and suffering from frost damage, which will affect their growth the following year. At the same time, in combination with tillage and soiling to protect the root system, before the land freezes, you can use horse manure, manure, dead grass, leaves and other materials to cover the root neck to protect it from frost damage.

Management after greening: The core of management at this stage is to balance the relationship between leaf growth and stem expansion. After returning to green, the leaves grow more vigorously, so management should be mainly control, reduce watering, increase the number of tillage, and apply diluted manure once with water to maintain soil moisture and increase ground temperature, promote the expansion of leaf area, lay the foundation for the expansion of the stem, and accumulate necessary nutrients. This is the stage of "controlled" growth.

Management during the vigorous growth period: During the growth of lettuce, when 5 or 8 leaves in the first leaf ring unfold to form a "cluster" state, the leaves grow rapidly and form a rosette shape. At this time, a quick-acting nitrogen fertilizer should be applied once to promote growth. When the second leaf ring is formed, the rosette leaves are fully developed, and the heart leaves are flush with the rosette leaves, the stem begins to swell. At this time, water should be applied and quick-acting nitrogen and potassium fertilizers should be applied to promptly switch from controlling growth to promoting growth. This watering is very critical and is the turning point for controlling and promoting growth.

If watering is done too early, it may cause excessive leaf growth, insufficient nutrient accumulation, and the stems to easily "shoot taller". At the same time, the seedlings become tender after watering, and if the temperature drops, they are susceptible to downy mildew. On the contrary, if watering is too late, excessive control will inhibit leaf growth, reduce the photosynthesis area, affect the full expansion of the stem, and suddenly increase water and fertilizer after a long period of drought, which may cause cracks in the stem. During the stem expansion period, the demand for fertilizer and water increases. The ground should be kept moderately moist, the water should be evenly distributed, and topdressing should be applied in appropriate amounts in several times to prevent stem cracks, which will affect yield and quality.

4. Harvesting method

The most critical part of harvesting spring lettuce is determining the best time to harvest. The ideal time to harvest spring lettuce is at the "flat" stage, which is easy to identify when the top of the main stem is on the same level as the tips of the top leaves. At the "flat mouth" stage, the stems of the lettuce have fully expanded, are crisp and tender, and are of superior quality. If the harvest time is delayed, the lettuce stalks will over-elongate, the fiber will increase, the flesh will become hard, and even become hollow, which will seriously affect its quality.

4. Autumn lettuce cultivation technology

Autumn lettuce sowing is usually scheduled from late July to early August. This period is the high temperature season, the temperature is high at night, and the plant respiration is vigorous, which can easily cause the plants to grow too tall. At the same time, high temperature and long sunshine will promote the rapid differentiation of lettuce flower buds and cause bolting. Therefore, cultivating strong seedlings and preventing early bolting are the keys to successful autumn lettuce planting. The following points need to be paid special attention to when planting lettuce in autumn:

1. Variety selection

Medium and late maturing varieties that are not sensitive to high temperatures and long days should be selected. Suitable varieties may vary from place to place, but it is important to choose varieties that are adapted to the local environment.

2. Cultivate strong seedlings

Before sowing, the seeds should be soaked and germinated at low temperature. Soak the seeds in cool water for 5 to 6 hours, then germinate them under light at a temperature of 15 to 18°C, and sow them when the radicle emerges 2 to 3 days later. It takes about 70 to 80 days from sowing to harvesting autumn lettuce, and the best temperature for stem and leaf growth is 40 to 50 days in the autumn when the average temperature drops to around 21°C. Therefore, it is recommended to sow 30 days before the average temperature of the ten-day period reaches 21 to 22°C. If sowing is too early, high temperature and long daylight will cause reproductive growth to exceed vegetative growth, resulting in bolting before the stems have expanded; if sowing is too late, the growing period will be shortened, affecting yield.

3. Planting

It is suitable to transplant when the seedlings are 25 to 30 days old and have four or five true leaves. If the seedlings are too old, they will easily grow excessively and cause "height leaps". Before planting, the seedlings must be strictly selected to remove those that are too tall, weak, or diseased. Compared with spring lettuce, the planting density of autumn lettuce is slightly larger.

4. Field management

After planting, shallow and frequent watering should be adopted until the seedlings have grown. After the seedlings have grown, apply quick-acting nitrogen fertilizer, then reduce watering times appropriately and perform deep tillage to promote root expansion. The second topdressing is carried out during the "clumping" stage, mainly using quick-acting nitrogen fertilizer to accelerate leaf differentiation and expand leaf area. Before ridge closing, the stems begin to swell, and then you may need to apply fertilizer one or two more times depending on the situation to ensure even distribution of fertilizer and water and avoid cracks in the stems, which would affect yield and quality.

5. Summer lettuce cultivation technology

The cultivation of lettuce in summer requires precise grasp of the following key steps:

1. Low temperature germination

Since the growing season of lettuce in summer is in the high temperature season, it is necessary to choose high temperature resistant varieties. Before sowing, the seeds should be germinated by soaking them in cold water for 8 to 12 hours until the water absorption rate reaches 70% to 80%. Then wrap them with wet gauze and put them in the refrigerator or hang them in a well. Keep them at a low temperature of 4 to 5°C for 24 to 28 hours. Then transfer them to a suitable temperature of 15 to 20°C to keep them moist and germinate. After about 2 to 3 days, when most of the seeds have white buds, they can be sown.

2. Shade seedling cultivation

Summer lettuce is usually sown in late June to early July. When sowing, it is best to mix the seeds with an appropriate amount of dry fine soil. When it is dry, water the seeds to create moisture before sowing. After sowing, shallowly rake and compact the soil, and build a shed with straw mats for shade. Cover it in the morning and evening on sunny days, and cover it all day on cloudy days to lower the temperature and maintain humidity. During the seedling stage, apply diluted manure water 2 to 3 times in combination with watering. Transplantation can be carried out when the seedlings are about 25 days old and have grown 4 to 5 true leaves.

3. Transplanting and planting

Before transplanting, apply 3,000 kg of decomposed manure and 2,000 kg of human and animal manure per mu, then prepare the land and dig ditches to make ridges. The ridges are 1.5 to 2 meters wide, the ditches are 25 centimeters wide and 15 to 20 centimeters deep. Choose a sunny evening in late July, water the seedbed, and then transplant the seedlings with soil. The plant spacing is 25 cm and the row spacing is 35 cm. Plant 700 to 800 plants per acre. After transplanting, water the plants sufficiently to ensure that they take root, and then water them with diluted manure water 2 to 3 days later. It is best to build a shed to provide shade before it takes root.

4. Field management

The roots of lettuce are shallow in summer, and its absorption capacity is weak. It grows rapidly in summer and has a greater demand for fertilizer and water. Therefore, special attention needs to be paid to fertilizer and water management. After the seedlings survive, apply diluted manure water every 3 to 5 days in combination with drought resistance. When the stems begin to swell, water and fertilize them frequently. Stop watering 10 days before harvest and spray 0.3% potassium dihydrogen phosphate on the leaves 1 to 2 times.

6. Cultivation technology of overwintering lettuce

1. Select excellent varieties and use covered seedlings

Select high-quality varieties that are popular in the market, and use mesh covering technology for seedling cultivation to protect the seedlings from the effects of cold weather.

2. Reasonable close planting and heat preservation to promote growth

Overwintering lettuce should be planted in clay loam or sandy loam that is rich in organic matter and has strong fertilizer and water retention capabilities. Apply sufficient organic fertilizer before planting, and apply human and animal manure in time after planting to promote the resumption of growth of seedlings. When the outside night temperature drops to 3-4℃, a shed should be built and covered with insulation materials. After covering, the growth rate of lettuce will accelerate. According to the growth of the plant, spray 40% chlormequat chloride 1000 times solution or 15% paclobutrazol 150 mg/kg 1 to 2 times in time to regulate the growth.

3. Strengthen fertilizer and water management

For overwintering lettuce, sufficient base fertilizer should be applied once before transplanting, with 4,000 to 5,000 kilograms of decomposed organic fertilizer and 40 to 50 kilograms of 45% nitrogen, phosphorus and potassium compound fertilizer applied per mu. After planting, when the leaves begin to grow, apply 1500 to 2000 kg of human and animal manure per mu, combined with 5 to 7.5 kg of urea or 10 to 15 kg of ammonium bicarbonate. When the fleshy stems begin to swell, apply 2 kg of urea and 10 kg of compound fertilizer per mu in combination with irrigation to ensure adequate nutrient supply.

7. Control techniques for main diseases and pests of lettuce

Common diseases of lettuce include downy mildew, sclerotinia rot, gray mold and Rhizoctonia basal rot.

Prevention and control measures for downy mildew:

1. Strengthen water management and field ventilation and light transmission to reduce humidity.

2. Implement chemical control: In the early stage of the disease, alternately use 600 times diluted 75% Benomyl wettable powder, 1000 times diluted Downy Mildew Killer, 800 times diluted DuPont, etc., spray once every 10 to 15 days, for 2 to 3 times in a row. If the disease progresses, the spraying interval needs to be shortened to control the spread of the disease.

Integrated control of Sclerotinia, Rhizoctonia basal rot and Botrytis cinerea:

1. Implement reasonable crop rotation to avoid continuous cropping.

2. Use mulch covering technology and add fertilizer and water under the film in a timely manner. The operation should be carried out on a sunny morning and ventilate in time to avoid excessive irrigation.

3. Appropriately reduce planting density to improve ventilation and light conditions.

4. Strengthen chemical control: After the disease occurs, alternately use 600 times diluted 50% procymidone, 1000 times diluted downy mildew net, 800 times diluted Dupont Clone, 1000 times diluted 40% Sclerotinia net, etc., usually spray once every 7 to 10 days, for 2 to 3 times in a row.

Common lettuce pests and their prevention and control:

The main insect pests of lettuce are aphids, whiteflies, cabbage loopers and American leafminers.

Aphids can be controlled by spraying insecticides such as cypermethrin, aphid-repellent, cypermethrin, and imidacloprid.

Whiteflies, cabbage worms, and leafminers can be controlled by using pesticides such as Bidan, Qianke, and Banqianjing.

The above is an introduction to the key points of lettuce cultivation technology. Lettuce is famous for its crisp flesh and bright green young stems. As it matures, its color will gradually change from bright green to white-green. This vegetable can be eaten in a variety of ways. It can be eaten raw, mixed with cold ingredients, stir-fried, dried or pickled. Its young leaves are also suitable for consumption. Lettuce is usually planted and cultivated in open air environments.