First, nursery:
1. Sowing time: Depending on the specific requirements of the crop, sowing can be done throughout the year. However, autumn sowing is most suitable for onions, with an average temperature range of 16.5°C to 17°C being ideal. This is usually around late October. The timing varies depending on the climate in different regions of the country. The best time is determined by the size of the seedlings before winter. It's essential to ensure they survive the winter and are ready for spring growth. The standard for pre-winter seedlings is when they have two leaves and one heart. Spring sowing typically occurs around the Qingming Festival.
2. Seedbed preparation: The nursery field should be flat, fertile, close to a water source, and well-drained. Before plowing, the soil should be lightly tilled. Apply 50 kg of compound fertilizer, 2.5 kg of Mushi skin Nan Dan, and 0.5 kg of carbendazim powder to kill pests and pathogens (this is very important). Create long beds of 20-25 meters, 1 meter wide, with 30 cm furrows and ridges. The ridges should be compacted and leveled using a rake, ensuring no uneven areas.
3. Sowing: Before planting, remove the top layer of soil and fill the bed with water (a large volume is necessary). After the water has soaked in, mix the seeds with sand and sprinkle them evenly twice. Finally, cover the seeds with soil, about 1.5-2 cm thick. Use 1.3 kg of seeds per 3-5 mu of green onions. The next morning, loosen the surface to prevent uneven coverage.
Second, seedling management:
After 7 days of autumn sowing, seedlings are transplanted in spring after 8-12 days. Control watering before cotyledons straighten to avoid siltation. During rain, lightly cultivate the soil. Water when cotyledons are straight. Weeding is required without herbicides. When seedlings reach about 2 cm, spray to prevent fungal diseases, usually every 5 days (mainly for root rot, virus, and gray mold). When seedlings grow over 5 cm, apply urea based on ground conditions.
Before winter, focus on cultivating strong seedlings. Standard: plant height 8-10 cm, true leaves reaching two leaves and one heart, green and sturdy, base diameter not exceeding 0.3 cm. Water 1-3 times based on soil moisture, and pour frozen water before freezing. Mix soil with woody ash or fine-circle fertilizer, ensuring leaf sheaths are not too thick.
After autumn seedlings emerge in spring, remove the sputum to eliminate debris, preventing excess moisture and promoting early growth. In the first ten days of March, avoid premature activity to prevent low temperatures from affecting growth. Combine watering with applying 10 kg of urea per acre. Late March to early April, when seedlings reach about 30 cm, thin 1-2 times, spacing up to 3-5 cm. Late April to early May, when seedlings reach about 50 cm, manage fertilization and water, apply urea and other fertilizers at least twice, each 10-15 kg, combined with spraying micro-fertilizer 2-3 times. Prevent fungal diseases and control onion flies and leaf miners. Stop watering 15 days before transplanting for stable growth.
Third, transplanting and planting:
1. Choose a terrain with good drainage and fertile soil. The best orientation is north-south. Apply 5000 kg of manure, 100 kg of fertilizer, 10 kg of urea, 15 kg of potash, or 30 kg of diammonium phosphate, or 50 kg of compound fertilizer. Plow the soil to dry it, eliminating disease sources, weeds, and improving fertility. Create ditches 80 cm apart, 25 cm deep and wide.
2. Suitable planting period is usually mid-June to early July. Before transplanting, water deeply to help roots establish. Remove soil and flatten the plants, discarding diseased seedlings. Sort seedlings by size, height, and thickness into three categories. Transplant while keeping green onions fresh. Plant spacing should be 3-4 cm.
3. Planting method:
Dry planting: After digging the ditch, arrange seedlings along the ditch wall at a certain spacing, with leaves flat against the wall, then cover with soil. Bury the soil deep but not the heart. Or use a shovel to plant at intervals and step on the soil. Water after planting. Avoid removing it immediately.
Hydroponics: Place selected seedlings on the back ridge, evenly spaced, and water the ditch first. After the water seeps through, place one person every 8-10 meters. When cutting, use peeled branches to make a plug, with a "V" fork. Hold the seedlings with your left hand and the stick with your right, inserting them into the wet soil at the bottom of the ditch. Different grades of seedlings should be planted in separate plots to avoid uneven growth.
Fourth, post-plant management:
After transplanting, during hot weather, high temperature, and rain, generally do not water. Rain can lead to root rot and dead seedlings, so drainage is crucial. In case of high temperature and drought, watering is needed to cool and promote growth. As the season progresses, earth, fertilizer, and soil cultivation should be carried out. The first topdressing starts from Liqiu, applying 5,000 kg of fertilizer and 10-15 kg of urea. The second topdressing in summer uses 15-20 kg of urea and 50 kg of cake fertilizer. Third topdressing in Bailu involves 1000 kg of manure and urine, 15 kg of urea, 50 kg of phosphate fertilizer, and 5-10 kg of potassium fertilizer. Spraying micro-fertilizer before and after Bailu, once every 5-7 days, up to 2-3 times, significantly increasing yield.
Fifth, harvest and storage:
Before and after winter begins, onions should be harvested in bundles of about 15 kg. Store them in a ventilated area, tying 5-6 lines together, spacing 50 cm apart. In high temperatures, unbundle to avoid heat damage. Storage should protect from rain and avoid excessive heat.
Sixth, main pests and diseases:
1. Leaf miner: Mainly harms leaves, larvae enter mesophyll, leaving white-lined paths due to chlorosis.
2. Onion fly: Mainly harms leaves, causing white spots, severe cases result in grayish-white leaves due to chlorosis.
3. Root rot: Mainly affects underground parts, causing stem rot and leaf withering, leading to lack of seedlings.
4. Green onion purple spot disease: Affects leaves, lesions expand from small white spots to 3-5 cm, fusiform or jujube-like, with dark purple, called purple spot disease.
5. Downy mildew: Diseased plants twist and dwarf, with yellow-white oval lesions, leaves droop and dry.
6. Scallion rust: Commonly known as red peony, a serious disease in green onion areas. Lesions appear on tubular leaves and stems, initially round, elliptical, or spindle-shaped, turning orange-brown, scattered, causing yellowing, drying, and falling, reducing production.
The above planting experience is for reference only. Each region should adapt based on local conditions and climate.
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