One, sowing seedlings 1 seed selection The varieties are mainly selected for high-quality, high-yield, strong stress resistance, strong adaptability, good commercial properties, and insensitive response to long-day sunlight. The Jiangsu area mainly adopts fine varieties such as Hongfei F1, Hongsheng F1, and Ziyang. 2 Sowing at the right time The selection of the onion sowing date should be based on the local temperature, light and maturity of the selected varieties. In Jiangsu area, planting is generally carried out from September 10 to 20, and the seedling age is controlled at 50 to 60 days. 3 Seedbed preparation The seedbed should be a plot with high dryness, convenient drainage and irrigation, and no onions and garlic for 2 to 3 years. After the first crop is harvested, shallow plough and fine rake in time, apply enough base fertilizer, and make flat borders. Generally, 3 000-3 500 kg of decomposed high-quality organic fertilizer is applied per acre of seedbed, and 400 ml of 50% phoxim EC is added with 6.5 kg of wheat bran, and mixed with organic fertilizer to prevent underground pests. Then plow the ground to mix the soil and fertilizer, raking, leveling, and bordering. Apply 40-50 kg of diamine phosphate and 25 kg of potassium sulfate per mu in the border. Use high headings to raise seedlings, borders with a width of 1.2 m, and borders with a width of 0.3 m. After the borders are made, they are steadfast, pour foot water, and sow after the water seeps down. Planting 1 mu of field onion requires 60～75m2 seedlings. 4 seeding method Soak the seeds with warm water at 50°C for 10 minutes before sowing; or use 50% thiram, 35% metalaxyl wettable powder, and 0.3% of the seed weight to dress the seeds. The seeds are mixed with 3 to 5 times the fine soil, and evenly sprinkled on the border surface, then covered with 0.8-1.5 cm thick fine dry soil, and covered with mulch film on the border surface. The sowing amount of 1 m2 seedbed is generally controlled at 2.5～3.0g. 5 Seedling management Generally, seedlings begin to emerge 7 days after sowing. After 60% of the seeds emerge, remove the mulch in the afternoon. Keep the seedbed moist after sowing. When "pull the bow" (the young stem grows to about 4 cm, the cotyledons of the plant are arched and stretched) and "stretch" (the upper half of the cotyledon pulls the lower half and the seed coat out of the ground), There must be no shortage of water. Properly control water about 15 days before planting to promote root growth. The seedling stage generally does not require top dressing. If the seedlings grow weakly, apply 5 kg of diammonium phosphate per mu of seedbed combined with watering. 6 strong seedling standards The standards for strong seedlings of onion vary depending on the variety and seedling season. Generally, the plant height is 15-18 cm, the pseudostem is 0.6-0.8 cm thick, with 3 to 4 leaves, and the seedling age is 50 to 60 days. The plant is robust and free of pests and diseases. 2. Reasonable colonization 1 Fertilization, soil preparation, and bordering For medium soil fertility, use 3000～4000kg of decomposed organic fertilizer, 15～20 kg of diammonium phosphate and 5～10 kg of urea per mu as base fertilizer. After fertilization, flatten and rake into a flat border with a width of 1.5～1.8 m, flatten the border, pour the sole water, use 72% metolachlor EC 50 ml or 33% pendimethalin EC 100ml per mu To 50 kg of water, spray evenly across the field to control weeds, and then mulch and compact it. 2 Colonization time Planting in Jiangsu is generally in mid-to-late November. 3 Colonization density The planting density of onions should be determined according to the variety, soil fertility and seedling size. Generally, the plant spacing is 15-16 cm, the row spacing is 15-18 cm, and 23 000-29 000 plants can be planted per mu. 4 classification of seedlings When planting, choose seedlings with well-developed root system, strong growth, and uniform size. After seedlings emerge, they should be classified according to seedling size, and diseased seedlings, weak seedlings, injured seedlings, and seedlings with pseudostem diameters greater than 0.9 cm or less than 0.4 cm should be eliminated. Colonize separately. 5 Colonization method Before planting, cut the roots of the seedlings to 2 cm, and then dip the roots with 50% carbendazim 500-800 times solution. When planting, the seedlings are planted according to the size level. First planting holes are made according to the plant and row spacing, and then the seedlings are planted into the planting holes. The depth of the planting is to bury the stems and not to bury the leaf holes. 3. Field management 1 watering Water planting water immediately after planting the onion, planting to overwinter, the temperature is low, the growth is slow, the irrigation should be properly controlled, mainly for cultivating moisture preservation, and the soil is sealed with frozen water once before freezing. After turning green in the second year, pour the green water in time to promote the green growth of the seedlings. Watering in early spring should not be too frequent during the leaf growth period. Keep the soil dry and wet. Generally, water once every 7-10 days. When the bulb begins to swell, you should properly control the water and squat the seedlings for about 10 days. After squatting the seedlings, the bulbs begin to swell, which is a key period for top dressing and irrigation. Stop watering 8-10 days before harvest. 2 fertilizing Topdressing in stages according to soil fertility and growth status. When turning green, add 10-15 kg of ammonium sulfate and 20-30 kg of superphosphate per mu. After returning to green, the plant enters the vigorous leaf growth period for the second topdressing, applying 15-20 kg of ammonium sulfate per mu. 50-60 days after turning green, 10 kg of nitrogen, phosphorus, and potassium ternary compound fertilizer was applied with water during the bulb swelling period, and applied again at an interval of 15-20 days. During the peak period of bulb swelling, fertilize appropriately as needed. The last top dressing time should be more than 30 days before the harvest. 3 pick buds, split stalks Early bolting often occurs during the growth of onions in spring. Bud picking and splitting are often used in production to promote the differentiation of lateral buds and obtain some yield. According to the experience of some vegetable farmers in Shandong and Tianjin, picking the stems from the base is not as good as removing the buds from the top of the flower stems in the early stage to avoid wasting nutrients. There is also the splitting method, which splits the flower stalk into two halves from top to bottom to promote the growth of lateral buds, squeezing the stalk to one side, and finally forms a more substantial bulb. Jishan Huayao 4. Disease and pest control In accordance with the plant protection policy of "prevention first, comprehensive control", agricultural control, physical control and biological control methods should be used first, and chemical control techniques should be used scientifically and rationally. During the growth period, use 75% chlorothalonil wettable powder 500 times solution or 70% mancozeb 500 times solution or 58% metalaxyl mancozeb 500 times solution to prevent purpura, and use 72% manganese zinc·cymoxanil wettable powder 600 times liquid or 64% frost·manganese-zinc wettable powder 600～800 times liquid to control downy mildew, use 40% pyrimethanil EC 1000 times liquid or 40% Botrytis cinerea suspending agent 1 200 times liquid to control ash mildew. In the early stage of adult occurrence of Liriomyza spp. and the larval leaf-mining stage of infestation, use 1.8% abamectin EC 2,000 to 3,000 times solution or 75% cyromazine wettable powder 3,000 times solution for control. 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