1. Seeding and seedling raising
Before disinfection and sowing, dry the seeds in the sun for 5-8 hours, then soak the seeds in water at 15-24℃ for 3-5 hours, then take out the seeds, drain the water, wrap them with clean and moist gauze, and germinate under light at 15-20℃.
Preparation and disinfection of nursery soil: mix the garden soil without lettuce for 3 years with fully decomposed organic matter (preferably cow and horse manure) at the ratio of 3: 1, and crush and sieve.
Disinfection of nursery soil: firstly, use high-temperature disinfection, that is, spread the prepared nutrient soil on the ground with a thickness of 8- 10cm, cover it tightly with plastic film after watering, and expose it to the sun for more than 5 days, so that the temperature under the film can reach 50-60℃, which can play a good disinfection role. When the temperature can be reached, try to choose high-temperature disinfection to reduce pesticide pollution; Disinfection with chemical agents: 50% carbendazim wettable powder and 50% thiram wettable powder can be mixed according to the ratio of 1: 1. The dosage is 8 8- 10/0g and15-30kg of fine soil, of which 2/3 is spread on the seedbed, and 1/3 is covered on the seeds after sowing.
2. Manage 2 leaves at seedling stage, 1, and the spacing between plants is 6-8cm. During spring crop cultivation, seedlings cultivated under protective facilities should be exercised for 7 days before planting. If pests and diseases are found, they should be pulled out in time and taken out of the field for centralized destruction.
3. Planting and field management:
Apply 2000-3000 kg/mu of decomposed organic fertilizer, 4 kg/mu of calcium superphosphate, 30 kg/mu of urea and 50 kg/mu of potassium sulfate for soil preparation and fertilization. Soil preparation should be no problem. After deep ploughing and leveling, the ridge is covered with plastic film, with a ridge width of 60cm, a trench width of 40cm and a ridge height of 15-20cm.
Planting time and method When planting in the 5-6 leaf stage, it is easy to bolting prematurely if the seedling age is too long. Two rows of ridged soil are planted with a spacing of 25-30 cm. When planting, strictly select seedlings, eliminate overgrown seedlings and pests, and plant in the afternoon in high temperature season.
4. Irrigation should be done in time after planting management to promote the slow growth of seedlings. Before the formation of rosette leaves, properly control water and squat seedlings to promote the development of root system and lush foliage. When the leaves are thick, two leaf rings have grown, and the heart-shaped leaves and rosette leaves are flat-headed, the stems begin to swell. At this time, water the squatting seedlings in time, apply available nitrogen and potassium fertilizers, and change control and promotion in time. Premature watering has many disadvantages. First, the leaves are white and long, nutrients cannot be accumulated, and the stems are easy to "escape"; Second, the leaves are tender after watering. If the temperature drops and the young leaves turn yellow, it will affect the leaf area. Third, if the temperature drops after watering, the seedlings are susceptible to downy mildew. Of course, it is too late to control watering excessively, so the growth of leaves is inhibited, the assimilation area is reduced, and the stem hypertrophy is also affected, and the stem is easy to crack after long-term drought.
Topdressing lettuce is generally carried out in three times. The first topdressing is urea 10 ~ 15 kg/mu within 7 days after survival, the second topdressing is urea 15 ~ 20 kg/mu when the stem begins to swell after squatting, and the third topdressing is 65438+ in the vigorous growth period of stems and leaves. Topdressing should be applied between adjacent plants, and each topdressing should be combined with irrigation.
Note: after watering, the stem hypertrophy speed is accelerated, and the water demand and fertilizer demand are increased. Water when the ground is slightly dry. The water content should be uniform, and the amount of topdressing should not be too large each time, otherwise watering after a long drought will easily cause cracks in the stems and premature bolting.
harvest
When the top of the main stem of lettuce is flush with the tip of the highest leaf (called "flat mouth" by the masses), the stem is fully expanded and crisp and tender. If the harvest is too late, the flower stems will become longer, the fiber will increase, the meat will become hard or even hollow, and the quality will be reduced. So we must pay attention to timely harvesting.
6. Pest control
6. 1 disease
In the early stage of downy mildew, the shriveled plants in the field are pulled out, taken out of the field and buried deeply. At the initial stage of the disease, 64% antiviral alum wettable powder is 600-800 times (at most twice, with a safe interval of 15 days), 75% chlorothalonil wettable powder is 500 times (at most three times, with a safe interval of 10 days) and 72.2% water repellent is 600-800 times (at most)
At the initial stage of botrytis cinerea, spray with 2000-fold solution of 50% Sukeling WP (maximum use 1 time, safety interval of 7 days) or 50% chlorpheniramine WP 1000-fold solution (maximum use twice, safety interval 10 day). Spray once every 7- 10 day, 2-3 times. Pay attention to alternate medication.
At the initial stage of Sclerotinia sclerotiorum, 50% solution of sucking buds 1000 times (used at most 1 time, with a safe interval of 7 days) and 50% solution of chlorpheniramine WP 1000 times (used at most twice, with a safe interval of 10 day) were sprayed for control, every other time. Pay attention to alternate medication.
6.2 pests
Whitefly traps and kills adults with yellow boards. Cultivate and plant insect-free seedlings. Chemical control should be carried out as soon as possible, and 10% imidacloprid wettable powder 1000-2000 times solution (used for up to 3 times with a safe interval of 7 days), 10% Uranus 2000 times solution (used for up to 3 times with a safe interval of 4 days) and 2.5% deltamethrin 2000 times solution can be selected.
Liriomyza huidobrensis timely cleaned the pupae on the plastic film and destroyed them centrally. Chemical control can choose 1.8% avermectin EC 2000 times solution (once at most, with a safe interval of 7 days), 10% imidacloprid WP 1000-2000 times solution (three times at most, with a safe interval of 7 days) and 2.5% kungfu EC 2000-3000 times solution. The best time to control adults is 8- 1 1 in the morning, and the best time to control larvae is 1-2. Note that different drugs should be used alternately.