What are the key points of onion seedling cultivation? Explained clearly in one article

1. Choose superior varieties. In the onion-producing areas of central and southern Hebei Province, vegetable growers can choose early-maturing red-skinned onion varieties, such as the Zi Xing, Zi Yu, Zi Yan and other series. These varieties have a strong pungent flavor, high yield and excellent quality, sell well for export, and are favored by foreign buyers. Generally, the yield per mu reaches about 5000 kg, and high yields can exceed 7500 kg.

2. Prepare the seedbed. The seedling bed should be a plot with loose, fertile soil and strong water retention that has not grown onions, garlic or similar vegetables within 2 to 3 years. Each mu of field requires about 35 sq m of seedbed area, and the usual seed rate is 0.5 kg. Before sowing, apply 1000 kg of fully decomposed farmyard manure, then 20 to 30 kg of compound fertilizer, then plow and prepare the soil finely, make beds 1.5 to 2 m wide, and water thoroughly before sowing.

3. Sow at the right time. The timing of sowing directly affects the size of the seedlings, and ultimately affects the yield and profit of the onions. Sowing too early extends the seedling growth period, causing oversized seedlings that are prone to bolting; sowing too late results in weak, small seedlings with low cold tolerance that easily die during overwintering. Therefore, to achieve high yield, you must grasp the optimal sowing period. Based on experience, in the vegetable areas of central and southern Hebei Province, the most suitable sowing time is 3 days before and after White Dew. Dry seed broadcasting is mostly used, and after sowing, cover with fine soil, preferably so the seeds are no longer visible. After covering with soil, each mu of seedbed can be sprayed with 100 ml of 33% pendimethalin to prevent and control weeds in the seedbed.

4. Seedling stage management. The focus of seedling stage management is cultivating strong seedlings. After sowing, cover the bed surface with a layer of wheat straw or shade netting, which helps retain moisture, prevent high temperatures and protect against rain. Before emergence, the soil should be kept moist at all times. When about 60% of the seedlings have emerged on the seedbed, the covering can be removed, and water should be sprinkled promptly according to the weather to prevent the seedbed from crusting. Combined with watering, 1% urea can be applied as a top dressing, regulating fertilizer and water to cultivate strong seedlings of the right age. It is necessary both to prevent the seedlings from growing too large and causing early bolting, and to avoid thin, weak seedlings that affect overwintering. Generally, when onion seedlings reach 4 true leaves, a plant height of 20 to 25 cm, and a leaf sheath diameter of 6 to 7 mm, they can be transplanted.

5. Transplant at the right time. When transplanting, the onion seedlings should be separated according to size so they grow uniformly, and large seedlings with a leaf sheath diameter over 8 mm, as well as weak, small seedlings under 3 mm and diseased seedlings, should be removed. Transplanting is generally completed from the end of October to early November, requiring an average daily temperature of 4°C to 5°C. Because onions need about 30 days from transplanting to resuming growth, they must be encouraged to develop a good root system before severe cold arrives, to prevent soil freezing from causing seedling death. The transplanting density is generally about 20000 plants per mu, with a row spacing of 20 cm and a plant spacing of 15 cm. The transplanting depth should preferably not bury the heart leaf (what farmers commonly call the "five-pronged fork"). After transplanting, water thoroughly to promote the survival of the onion seedlings. Never flood-irrigate the whole field, so as to avoid soil crusting.