Detailed Explanation of Welsh Onion Seedling Cultivation Techniques, the Whole Process from Sowing to Management
I. Variety Selection: Mainly Japanese imported varieties such as Mingxing F1, Yuanzang, Changbao, Hanchun F1, etc.; Domestic varieties: Zhenyu Giant Onion, Tiegan, Moyu Giant Onion, Zhangqiu Welsh Onion, etc. II. Sowing Time and Seedling Age: Choose loose and fertile land with high organic matter content. Because Welsh onion dislikes continuous cropping, plots where allium crops were previously grown...
I. Variety Selection
Mainly Japanese imported varieties such as Mingxing F1, Yuanzang, Changbao, Hanchun F1, etc.; Domestic varieties: Zhenyu Giant Onion, Tiegan, Moyu Giant Onion, Zhangqiu Welsh Onion, etc.
II. Sowing Time and Seedling Age
Choose loose and fertile land with high organic matter content. Because Welsh onion dislikes continuous cropping, plots where allium crops were previously grown cannot be used. Imported early-maturing varieties cultivated in protected facilities are sown in early March and harvested from late October to early January of the following year; those in open fields are sown in late March to early April and harvested from November to January of the following year, with a seedling age of 55-60 days. Mid-maturing varieties are sown in early April and harvested in January-February, with a seedling age of 50-55 days. Late-maturing varieties are sown in mid-to-late April and harvested in late February to early March, with a seedling age of 50-55 days. Domestic varieties, depending on different harvest times, can be raised in small arch sheds in March and April, in open fields in May, June, September and October, and in greenhouses in October and November.
III. Seedbed Preparation
Seeds are expensive, so seedling transplanting should be used in production. The seedbed should be selected from sandy loam fields with loose and fertile soil, flat terrain, and convenient drainage and irrigation, where allium crops have not been grown in the previous 3 years, and deep-plowed and sun-bleached in alternate years. For nutrient soil preparation, use 6 parts of garden soil where onions have not been grown for 3 years plus 3 parts of fully decomposed organic fertilizer, crush and mix thoroughly. Prepare the land and make beds 5-7 days before sowing. According to soil fertility conditions, apply 20 kg of organic fertilizer and 6-8 kg of compound fertilizer per 80 square meters of bed, evenly spread on the bed surface and fully mixed with the soil. To prevent damage from underground pests, use 75-100 g of phoxim emulsifiable concentrate, add 4-5 times water, mix with 1.5 kg of bran, evenly spread on the bed surface, shallow hoe once, then rake level with a rake, immediately tread once with feet to prevent unevenness after irrigation and uneven soil covering that affects emergence, and finally water and sow.
IV. Seed Soaking
Use new seeds of the current year, 200 g of seed per mu of Welsh onion. Soak seeds for disinfection before sowing. Method 1: Soak seeds in 300 times diluted 40% formaldehyde solution for 3 hours, then rinse clean with water, which can prevent purple blotch; Method 2: Soak seeds in 0.2% potassium permanganate solution for 25 minutes, then rinse clean with water, which can kill pathogenic bacteria on the seed surface; Method 3: Wrap seeds well in clean gauze, place in warm water at 50°C and soak for 30 minutes. Shake continuously during soaking to heat the seeds evenly. After soaking, immediately rinse once with water, then soak in water at 20-30°C for 2 hours, remove and sow. Seeds after soaking can emerge 1-2 days earlier.
V. Sowing and Seedling Raising
Broadcast sowing. Before sowing, water the bed sufficiently. After the water fully infiltrates, mix seeds with fine dry soil or fine sand and sow evenly. After sowing, cover with soil 0.5-1 cm thick, then cover with plastic film or set up an arch shed to increase temperature and preserve moisture, keeping soil moisture sufficient. When onion sprouts emerge, immediately remove the plastic film. From seed germination to the cotyledon extension stage, the temperature should be above 7°C, with the optimum temperature being 20°C. When emergence reaches more than 60%, promptly remove the plastic film. From the first true leaf to before transplanting, maintain the appropriate temperature at 17-25°C. Do thinning work well: the first thinning removes higher-density seedlings, the second thinning finalizes the stand, removing diseased and inferior seedlings. When seedlings have 2-3 leaves, combined with watering, apply 1-2 kg of urea or compound fertilizer. The green-returning water during the seedling stage should not be applied too early; it should be done when the daily average temperature is above 13°C, to avoid yellowing of onion leaves caused by lowered soil temperature. For those who watered wintering water before overwintering without topdressing, green-returning fertilizer can be applied together with green-returning water, namely "seedling-lifting fertilizer," to promote seedling growth. Then pay attention to seedling hardening to promote root growth. After 15 days of seedling hardening, seedlings enter the vigorous growth stage, and growth speed significantly accelerates. Gradually increase irrigation frequency, and apply about 3-5 kg of urea per mu to meet seedling growth needs. But 10-15 days before transplanting, pay attention to controlling fertilizer and water to prevent onion seedlings from becoming tender and reducing survival rate after transplanting. When onion seedlings have 8-9 leaves, stop watering and harden the seedlings in preparation for transplanting. In principle, herbicides are not used in Welsh onion seedling beds, but in the later stage of seedling raising, if weeds are excessive, consider appropriately using herbicides such as efficient haloxyfop to kill weeds. Seeds used for seedling raising per mu can supply about 7-8 mu of field planting.
VI. Pest and Disease Control
For pest and disease control during the seedling stage, observe frequently, detect early, and control early, to ensure full, uniform, and strong seedlings. Main seedling-stage diseases include damping-off and gray mold, which can be sprayed with 1500-2000 times diluted 50% carbendazim wettable powder at the early stage of disease. Welsh onion downy mildew can be sprayed with fungicides such as Baijunqing, carbendazim, metalaxyl-copper, Duxolv, aluminum phosphite, and efficient onion fungicide. Viral diseases are transmitted by piercing-sucking mouthpart insects (such as aphids), and attention should be paid to their control. Main seedling-stage pests include onion thrips and leaf miners, which can be sprayed with 2000 times diluted 1.8% abamectin emulsifiable concentrate plus 1000 times diluted 10% imidacloprid wettable powder for control.