Spring lettuce,1February-March greenhouse seedling, mid-February to late March open field seedling. Summer lettuce is cultivated in the open field from April to mid-May, covered with sunshade net from late May to July, and planted directly or in high density. Autumn lettuce, covered with sunshade net from July to September, seeded and transplanted. Overwintering lettuce, 10- 1 1 seedling in the open field.

Planting technique

First, seed treatment:

Seeds sown in May-September are difficult to germinate due to the intense heat and high temperature, so they need to be germinated at low temperature before sowing. That is, the seeds are soaked in cold water for 6-7 hours, wrapped with wet cloth and germinated at 20-25℃ until the seeds are 80% white. Or soak the seeds in cold water for 1-2 hours, wrap them with wet cloth, place them in the ground 30 cm away from the water surface, spray water for 1-2 times a day, and germinate for 3-4 days, or soak the seeds for 24 hours, wrap them with wet cloth, put them in a refrigerator or freezer, freeze them at-3--5℃ for 24 hours, and then freeze them.

Second, the whole soil

Select a high-lying, dry and well-drained plot as the seedbed, and apply 4000-5000 kg of decomposed organic fertilizer or 500 kg of compound fertilizer as the base fertilizer 5-7 days before sowing. Apply before soil preparation, then dig deeply, level, cover with plastic film, and wait for sowing.

Third, sowing:

1. Spring lettuce, when raising seedlings in greenhouse, first uncover the film on the seedbed, water the soles of the feet, mix the seeds with a small amount of fine sand or fine soil after the water seeps out, and then sow. 10 square meter seedbed 25-30g. After sowing, cover the soil by 0.30-0.50 cm, cover the film tightly, and cover the sunshade net or straw mat for heat preservation at night. Use a small arch shed to raise seedlings in the open space.

Before the seedlings are unearthed, the plastic film should be uncovered late and covered early, and the bed temperature should be raised without ventilation. After the seedlings are unearthed, properly ventilate, and keep the bed temperature 12-20℃ during the day and 5-8℃ at night. The sunshade net is exposed early and covered late, and 2-3 real leaves are planted 1 time, and the seedling spacing is 4-5 cm. 5-6 days before transplanting, increase ventilation and temper seedlings.

2. Lettuce is sown on cloudy days in summer. Sow wet seeds to cover the film in the first half of April-May, and remove it after emergence. From the end of May to the beginning of July, cover the sun-shading net with a small arch shed or flat shed until seedlings emerge or two real leaves appear. Cover with sunshade net in rainy days to prevent rain from washing away. 10 square meter is used for sowing 5- 10 gram. The seedling spacing before 2 true leaves is 1 time, the time between 4-5 true leaves is 1 time, and the seedling spacing is 10 cm.

Healthy seedlings can also be planted at high density according to the row spacing of 10 cm. After each plant spacing, seedling fixing and transplanting, cooperate with watering and apply decomposed dilute manure. Clear ditches and drain water stains in rainy days, and water 0.50% urea solution 1 time about 5 days before planting. About 25 days after seedling formation or transplanting, the seedlings can be harvested one after another and put on the market.

3. Before sowing autumn lettuce, wet the seedbed thoroughly. After sowing, cover with 1 layer of 3-40% decomposed pig manure residue and 1 layer of thin straw, or cover with black sunshade net, and sow germinated seeds or wet seeds. Before emergence, cover the seedbed soil with a double floating surface, and after emergence, cover it with a silver-gray sunshade net. Water and fertilize in the morning and evening, keep the bed soil moist and weed in time.

Extended data:

High-yield techniques of lettuce in summer

Summer lettuce has shallow roots and weak absorption capacity. In addition, plants grow rapidly in summer and need more fertilizer and water. Therefore, more attention should be paid to fertilizer and water in field management in order to help plants grow sturdily. After the seedlings survive, dilute manure water should be applied every 3-5 days, and vegetable Zhuangganling should be sprayed for 3 times continuously, so as to improve the water and fertilizer absorption capacity of the plants, promote the lettuce stems to be strong, the leaves to be fresh and tender, and the yield to be high and excellent.

Lettuce is a cold crop, which is not resistant to high temperature. In summer, varieties with heat resistance, disease resistance and high yield should be selected, and seeds should be soaked before sowing to accelerate germination. The seeds can be soaked in cold water for 8- 12 hours. When the water absorption of the seeds reaches 70%-80%, they are wrapped with wet gauze, stored at 4-5℃ for 24-28 hours, and placed. Spraying new high-fat film in time after sowing can preserve moisture, activate the hardening density of the surface and improve the emergence rate.

The harvest period of lettuce in summer is also the fastest bolting period. If it is not harvested in time, the quality of lettuce will become hard or even hollow after bolting, which will greatly affect the yield and quality of lettuce. Therefore, lettuce should be harvested in time. When the top of the main stem of lettuce is flush with the top of the highest leaf, it is suitable for harvesting, and pesticides are prohibited 10 day before harvesting.

Planting and management

When planting, loam with good drainage conditions is selected, and 4000-5000 kg of decomposed organic fertilizer is applied per mu. Deep ploughing, leveling, ridging, width1.20-1.50m. Water the seedbed before seedling raising.

Spring lettuce, seedling age 25-30 days, 5-6 leaves, plant spacing 20 cm× 27 cm, depth should be buried at the base of the first petiole. Water it after planting. Listed as leaves, plant spacing 15cm× 20cm. In plastic film mulching cultivation, base fertilizer should be applied at one time, and plastic film should be covered in rainy days to prevent waterlogging. In greenhouse and open field, cultivate 1-2 times in warm sunshine, water topdressing in time, and irrigate light fertilizer frequently in the early stage to keep the border moist. When the factory is basically closed, tender plants can be put on the market. For the stalks, apply urea15kg 0-2 times per mu.

Autumn lettuce, planted at the age of 25 days, with a row spacing of 25 cm× (30-35) cm, is listed as a tender plant with a row spacing of 15 cm× 20 cm. After planting on cloudy days or in the afternoon, water it in time, and cover the greenhouse, small arch shed or flat shed with sunshade net to slow down the emergence of seedlings. Less intertillage, shallow intertillage, light manure irrigation, keep the soil moist, and apply 3000-4000 kg of urea or 15 kg of urea 2-3 times per mu before and after the plant closing period.

Lettuce in winter, seedbed bottom fertilizer should not be too full. When the seedlings are about 40 days old, they are planted with plastic film, and the row spacing between plants is (30-35) cm× (30-40) cm. After survival, apply 1-2 times of light manure water. If it is a mature plant listed in the second year, attention should be paid to hardening seedlings before overwintering, and fertilization and watering should not be too frequent to prevent excessive growth at seedling stage. Before freezing, apply 1 times antifreeze fertilizer water. Weeds were cleared in time in the spring of the following year, with shallow intertillage 1 time, and the concentration of topdressing increased from small to large. After the stem base began to swell, the number of topdressing decreased and the concentration decreased. If plastic film and greenhouse cultivation are used, single fertilizer should be applied and ventilation management should be paid attention to.

Collect and collect seeds

Seedlings can be harvested and put on the market at any time before the stems are completely enlarged. When the top of lettuce is flush with the highest leaf tip, it is the suitable time to harvest lettuce stems. In order to prolong the marketing period and delay the harvest of autumn lettuce, the growing points and buds can be pinched off by hand in sunny days, or 350-500 mg/kg chlormequat chloride can be sprayed 2-3 times every 5-7 days from the fruiting stage, or 2500 mg/kg chlormequat chloride can be sprayed twice every 5 days when the base is hypertrophy.

Lettuce seed collection can better preserve winter and spring lettuce seeds, and the preserved plant varieties are about 1000 meters apart. Select and keep the plants that grow vigorously and have the characteristics of this variety. After thinning, keep the plant spacing above 33 cm square, remove old leaves, increase fertilizer and soil, and promote the growth of lateral branches. When flowering, some branches should be properly removed and pillars should be inserted to prevent lodging. You can't lack water during flowering. After flowering, irrigation should be reduced. After 20-25 days, the leaves of the seed plants turn yellow normally, and the seeds are brown or silvery gray. After the white crown hair is born, it should be harvested in time. ?

disease control

First, botrytis cinerea

The fungus harms leaves and stems. The diseased spots on leaves are initially soaked in water, and then become irregular grayish brown spots after swelling. When the humidity is high, a layer of botrytis cinerea is produced on the diseased spots. When the stem is infected, firstly, water spots are generated at the base, then the stem base rots, and after expansion, a grayish brown or grayish green mold layer is generated. High temperature drying, the diseased plant gradually dried up and died; Under wet conditions, the diseased plants fester upward from the base.

The pathogen overwinters in the soil as sclerotia or conidia, and in the second year, the sclerotia germinates to produce mycelium with conidia, which is spread by airflow. Bacteria like warm and high humidity environment, the optimum temperature is 20-25℃, and the relative humidity is about 94%.

Prevention and control methods:

At the initial stage of the disease, spray 50% Lysol WP 600-700 times, 28% Grifola frondosa WP 600 times, 50% mirex WP 600-800 times, 50% procymidone WP 1500 times, or 40% Grifola frondosa WP 1200 times. These drugs are used alternately. According to the disease, spray 1 time, 7- 10 day, and control continuously for 3-4 times.

Second, downy mildew

This is the main disease of lettuce. Both spring lettuce and autumn lettuce occur, especially spring lettuce, which is most likely to occur in the harvest period of spring lettuce. This disease mainly harms leaves. First, there are nearly round or polygonal pale yellow spots on the leaves near the ground, and white mold grows on the back of the leaves. Subsequently, the diseased spots turned brown and joined together, and the whole leaves turned yellow and died, and quickly spread to the whole plant. A few days later, the plants in the whole field were damaged and withered, which was too serious to be harvested.

Pathogens overwinter in soil or autumn lettuce, and seeds can also carry bacteria. Generally, in spring and autumn, the plots with low temperature, much rain, much dew, foggy, less light, single variety, poor disease resistance, insufficient base fertilizer, excessive density and poor ventilation and drainage are seriously ill.

Prevention and control methods:

1, agricultural control measures: select disease-resistant varieties; Rotating; Proper control of planting density: applying sufficient fertilizer, increasing phosphorus and potassium fertilizer, strengthening water and fertilizer management at seedling stage, ditching and drainage, furrow irrigation and fertilization, etc. To reduce the humidity in the field. Timely prevention of rosette stage, transfer of patients and disabled persons after harvest, etc.

2. Seed dressing with a seed weight of 0.3%. Seed dressing can also use 25% poisonous bacteria (25% metalaxyl) or 50% thiram, metalaxyl, manganese and zinc.

3. Pesticide control: Pesticides should be sprayed at the initial stage of the disease, and the proportion of pesticide is: Antaisheng 70% wettable powder 1 kg water 1 700kg, Merck 66.8% wettable powder1kg water 700kg. 500 kg of 25% metalaxyl 1 kg water, 250 kg of 40% ethyl phosphate 1 kg water, 400 kg of 64% antiviral alum 1 kg water, 500 kg of 48% Du Rui manganese zinc 1 kg water, and 62.2% Pulik aqueous solution.

Common drugs such as chlorothalonil, antiviral alum, foscarnet sodium, and toxic mold also have effects. Spray with water every 7- 10 days 1 time, and spray continuously for 3-4 times. Spraying is mainly on the back of leaves. Chemical agents should be used alternately to improve the control effect and delay the emergence of drug resistance. ?

Third, viral diseases.

Lettuce infection is generally characterized by mosaic, severe dwarfing and yellowing. Non-sustainable transmission of virus by fruit juice and peach aphid.

Prevention and control methods:

Pay attention to the prevention and control of aphids, and choose Aimeile, aphid fog, etc. Or use 1000 times of Jinguguan solution or 1000 times of 50% carbendazim solution. Every 7- 10 days 1 time, 3-4 times in a row.

References:

Baidu encyclopedia-lettuce (Compositae)