How to sow and raise seedlings in autumn delayed cultivation of celery?

The delayed cultivation of celery in autumn is to raise seedlings in the open field. The seedling is 50-60 days old, with 4-5 true leaves, a height of 15-20 cm and a well-developed root system. Many localities sowed and raised seedlings in early August and planted in late September; New year's harvest. Or sow in the middle or late August, plant in early October, and harvest around the Spring Festival. In order to cultivate strong seedlings, we should pay attention to the following: (1) preparation of seedling border: celery seed is small, top soil capacity is weak, seedling emergence is slow, suitable seedling land should be selected and fine soil preparation should be made. Celery seedling land should choose higher topography, loose soil, irrigation and drainage, fertile sandy soil as seedling bed. Apply 5000 kilograms of rotten ring fertilizer per mu, turn it deeply and rake flat to make a flat bed with a width of 1.2 to 1.5 meters and a length of about 20 meters. When making the border, take out part of the border soil and sift it to cover the soil. After fine raking, spray the border surface with 48% fluralin per mu with 60 kilograms of water and immediately hoe 5 kilograms to 10 centimeters deep, so that the medicine and the topsoil layer are mixed evenly to prevent trifluralin photolysis. The weeding effect of trifluralin was 2-3 months. (2) seed soaking and sowing: seed soaking began 7 ~ 10 days before sowing. Soak the seeds in clean water for 24 hours, then rub and rinse the seeds until the water is clear, remove the seeds and hang them on the straw mat, so that the seeds lose excess water on the surface. After drying, put the seeds in an earthen pot, cover them with a wet cloth, and place them at 15: 20 ℃ to promote germination. During sprouting, turn the seeds once a day with clean water to make the temperature and humidity uniform. Wash the seeds with clean water every 2 days to prevent mildew. In about 7 days, 80% of the seeds can be sown when the seeds are white. Soak the seeds with 1000ppm gibberellin or 1% thiourea for 10 minutes, rinse the solution, soak with clean water, and then accelerate germination, the effect is better. Pour bottom water before sowing and smooth the border with a rake with water. The germinating seeds were slightly dried and mixed with a small amount of fine soil, and the seeds were sown evenly after the infiltration of water in the border. After sowing, the soil is covered by 0.5 cm by 1.0 cm. The sowing rate of seedling field is 1: 1.5 kg per mu, and the seedlings can be planted to 4 mu. (3) Post-sowing management: after sowing, cover the seedling border with grass curtains or defoliated straw, and the mulch had better not touch the border surface directly and put it on the ridge. The function of the mulch is to shade and cool down and prevent rain from slapping the border surface directly when it rains. When there is no rain during the emergence period, small water should be watered frequently to keep the border surface moist. After emergence, the grass curtain will be opened every morning and evening, so that the seedlings can see the light, and then cover the grass curtain for shade when the weather is hot at noon. As the seedlings grow up, the shading time becomes shorter and shorter every day, and the curtain will no longer be covered after more than 10 days. If the straw is covered with a ridge on the border, the seedlings will remove part of the straw every 2-3 days and finish it in 3-4 batches. If the herbicide is not applied before sowing, after sowing and covering the soil, spray 200 times of 25% herbicide ether to the border surface, 70 kilograms per mu. After the first true leaf was unfolded, the seedling distance was about 1.5 cm. The second true leaf is interspersed for the second time, and the seedling distance is 3 cm. At the same time, seedlings should pay attention to pulling weeds. During this period, pay attention to watering, keep the border surface moist. The seedlings were topdressing 10 kg of ammonium sulfate per mu and watering them when they were in 4-5 leaves, and then the watering times were reduced appropriately. Pay attention to the prevention and control of diseases and insect pests during seedling breeding. Use dimethoate to control aphids when there are aphids. Use chlorothalonil to control spot blight or spot disease.