Detailed Explanation of Key Techniques for Autumn Sowing and Seedling Raising of Welsh Onion

Autumn sowing and seedling raising of Welsh onion is generally carried out in early September. Sowing too early makes bolting due to vernalization likely, while sowing too late makes the seedlings prone to being killed by frost. Before overwintering, the seedlings should have 2-3 leaves, a plant height of about 10 cm, and a pseudostem base of less than 0.5 cm. Seed treatment: soak the seeds in clean water and stir for 10 minutes, remove the shriveled seeds and impurities, then place the seeds in warm water at about 65°C and scald them for 20-30 minutes while stirring constantly. Soaking the seeds can advance emergence by 1-2 days.

Sowing:

Use new seeds of the current year, with a sowing rate of 3-4 kg per mu, which can provide seedlings for planting 6-8 mu of land; if old seeds from the previous year are used, the seeding rate should be increased by more than double, and seeds more than two years old cannot be used. Broadcasting and drilling can both be used when sowing. Irrigate the seedbed with enough bottom water, sow evenly, then cover with about 1 cm of fine soil. For drilling, open shallow furrows 1.5-2 cm deep in the bed at a row spacing of 12 cm, sow the seeds in the furrows, and rake the bed surface smooth. Management: Before and after emergence of Welsh onion, keeping the seedbed moist is necessary to ensure normal emergence of the seedlings. After emergence and before overwintering, generally do not water unless dry; water and fertilize according to the use of base fertilizer and the growth of the seedlings. Before the soil freezes, water once with freezing water. In the following year, when the onion seedlings turn green and the daily average temperature rises to 13.5°C, begin watering with green-up water and at the same time apply green-up fertilizer; thereafter, thin the seedlings, cultivate, control water, and harden the seedlings for 12-15 days. After hardening, the onion seedlings enter the vigorous growth period, during which 2-3 rounds of watering and topdressing should be carried out. Apply 20-30 kg of urea per mu. Thinning: Thinning generally must be carried out twice; for autumn-sown seedlings, it is done during the seedling recovery period after the green-up water is applied in the second year, with a seedling spacing kept at 2-3 cm; the second time is when the seedlings are about 20 cm tall, with about 140,000 seedlings actually retained per mu. For drilled seedling beds, the above requirements can be followed by reducing the plant spacing to maintain sufficient nutritional area for each individual plant.

Cultivating strong seedlings:

The standard for strong seedlings is a plant height of around 50 cm, a white stalk length of around 25 cm, dark green leaf blades, 5-6 leaves retained, and a single plant weight of more than 40 g.

Pest and disease control:

Pests are relatively mild during the seedling stage of Welsh onion, but once found they must be controlled promptly.