Detailed Explanation of Key Points for High-Yield Welsh Onion Cultivation Techniques
I. Seedling raising: 1. Sowing time: It can be sown in all four seasons according to different requirements for the product. The best sowing period for high-yield cultivation of Welsh onion is autumn sowing (when the average temperature per ten-day period is stable at 16.5°C-17°C, which is exactly early October). The climatic conditions in the north and south of the country differ, so the sowing time also varies. The best time is determined by...
I. Seedling raising:
1. Sowing time: It can be sown in all four seasons according to different requirements for the product. The best sowing period for high-yield cultivation of Welsh onion is autumn sowing (when the average temperature per ten-day period is stable at 16.5°C-17°C, which is exactly early October). The climatic conditions in the north and south of the country differ, so the sowing time also varies. The best time is determined by the size of the seedlings before overwintering. If too large, they easily pass through vernalization and bolt the following spring; if too small, they cannot overwinter safely. The standard for pre-winter seedlings is to grow to two leaves and one heart. Spring sowing is around Qingming Festival.
2. Preparing the seedbed: The seedbed should be selected from a plot that is flat, fertile, close to a water source, and convenient for drainage. Before making the beds, the seedling-raising land should be shallowly plowed and finely harrowed so that the top is loose and the bottom is firm. Apply 50 kg of compound fertilizer per mu as base fertilizer, and 0.5 kg of carbendazim powder to kill underground pests and pathogens (very important). The bed is 20-25 m long, 1 m wide inside, with a bed ridge of 30 cm. After the bed ridge is tamped firm, use an iron rake to repeatedly level the inside of the bed until there are no clods.
3. Sowing: Before sowing, first take out the covering soil from the bed, then irrigate the bed with enough water (the irrigation amount must be large). After the water has infiltrated completely, mix the seeds with sandy soil and broadcast them twice in the bed (spread evenly). Finally cover with soil, with a covering thickness of 1.5 cm-2 cm. The covering soil must be even. The seed dosage for the seedling-raising field is 1.3 kg per mu, which can transplant 3-5 mu of Welsh onion. On the morning of the second day after sowing, use an iron rake to lightly rake the bed surface once to prevent uneven covering soil.
II. Seedling stage management:
1. Autumn-sown seeds emerge 7 days after sowing, and spring-sown seeds emerge 8-12 days after sowing. Before the cotyledons straighten, control watering to avoid crusting and smothering the seedlings. If rain occurs during this period and the soil crusts, use an iron rake to lightly break the surface. The first watering should wait until the cotyledons straighten. Weed (herbicides cannot be used). When the seedlings grow to about 2 cm, roughly when they straighten, apply pesticide in time to prevent fungal diseases. Generally spray once every 5 days (mainly using pesticides for treating dead roots and rotten seedlings, viruses, and gray mold). After the seedlings grow to more than 5 cm, apply urea as appropriate according to soil fertility to promote seedling growth.
2. Before winter, the main task is to cultivate strong seedlings. The standard is: plant height 8-10 cm, true leaves reaching two leaves and one heart, leaves green and robust, basal diameter not exceeding 0.3 cm. During this period, water 1-3 times according to soil moisture. Before freezing, water with freezing water, and generally cover with a layer of farmyard manure, plant ash, or fine pen manure, with a thickness such that the ground is not visible and the leaf sheaths are exposed.
3. After the Beginning of Spring for autumn-sown seedlings, the roots, hearts, and leaves of the onion seedlings begin to sprout. Rake the bed surface all over once to remove debris to prevent pressing the seedlings, achieve moisture retention, increase temperature, and promote early growth. In early March, water with green-returning water, but not too early, to avoid low temperatures affecting early growth of the onion seedlings. Combined with watering, apply 10 kg of urea per mu to promote seedlings. From late March to early April, when the seedlings are about 30 cm tall, thin the seedlings 1-2 times, thinning where dense and filling where sparse, maintaining a seedling spacing of 3-5 cm. From late April to early May, when the seedlings are about 50 cm tall, this is the vigorous growth period of the onion seedlings. Do a good job in fertilizer and water management. Apply urea, diammonium, compound fertilizer, etc. in stages as appropriate, at least twice, at most three times, 10-15 kg each time, and combine with pesticide spraying to apply compound micro-fertilizer 2-3 times. Also apply pesticide in time to prevent fungal diseases, with special attention to preventing and controlling onion maggots, onion thrips, and leafminers. Stop watering 15 days before transplanting and carry out seedling hardening to promote steady growth.
III. Transplanting and field planting:
1. Select a plot with high terrain, good drainage, and fertile soil, preferably oriented north-south. Apply sufficient base fertilizer. The base fertilizer can be 5000 kg of farmyard manure per mu, 100 kg of phosphate fertilizer, 10 kg of urea, 15 kg of potassium fertilizer, or 30 kg of diammonium, or 50 kg of compound fertilizer, then plow and sun the soil to eliminate disease sources and weeds and improve fertility. Finally, open furrows with a furrow spacing of 80 cm and a furrow depth and width of about 25 cm each.
2. Plant early at the appropriate time, generally from mid-June to early July. Water once two days before lifting the seedlings. When lifting seedlings, dig deep to remove the roots, or lift them in handfuls, shake off the soil, and place them flat. Eliminate damaged and diseased seedlings. Grade them into three levels according to size, height, and thickness. When seedlings are sufficient, generally do not use the third-level seedlings. Lift seedlings, grade them, and transplant them at the same time so that the onion seedlings remain fresh when transplanted. The transplanting spacing is preferably 3-4 cm.
3. Field planting methods: (1) Dry planting method: After opening the furrow, arrange the onion seedlings in order along one side of the furrow wall at a certain spacing, with the onion leaves lying flat against the furrow wall, then use a hoe to cover with soil. The soil covering depth should preferably not bury the heart leaves. After planting, tamp firm. Or use a shovel to plant at a certain distance, then tamp firm. After planting, water once immediately, preferably without delay. (2) Water planting method: Place the selected seedlings on the back ridge in handfuls of one meter, arrange them evenly. Water the furrow first. After the water infiltrates, one person every 8-10 m squats on the back ridge and inserts them. When inserting, use a rice-planting stick made from a peeled tree branch with a "v"-shaped fork at the top. Mostly use the left hand to hold the seedlings and the right hand to hold the rice-planting stick, use the fork to press against the fibrous roots of the onion seedlings, and while the soil at the bottom of the furrow is wet and soft, insert the onion seedlings straight down. Seedlings of different grades should be planted in different plots or in separate sections, and should not be placed side by side with tall and short mixed unevenly, so as to facilitate management.
IV. Management after field planting:
After transplanting, it is the hot season with high temperature and frequent rain, so generally do not water. Continuous overcast and rainy weather can cause root rot and dead seedlings, so pay attention to timely drainage. If high temperature and drought occur, water to lower the temperature and promote growth. As the white stalk continues to elongate, earth up and topdress in time. The final ridge height after earthing up is 70-80 cm. When earthing up, do not bury the heart leaves. Topdressing and earthing up are carried out at the same time. The first time should start from the Beginning of Autumn, applying 5000 kg of farmyard manure per mu and 10-15 kg of urea, followed by watering. The second topdressing is carried out at the End of Heat, applying 15-20 kg of urea per mu and 50 kg of cake fertilizer. The third topdressing is at White Dew. At this time, the white stalk enters the peak expansion period, and fertilizer and water management is key. Along the furrow, apply 1000 kg of human excrement and urine, 15 kg of urea, 50 kg of phosphate fertilizer, and 5-10 kg of potassium fertilizer, then water. The fourth topdressing is carried out at the Autumn Equinox, applying 10-15 kg of urea per mu, then earth up and water. Around White Dew, spray compound micro-fertilizer, generally once every 5-7 days, continuously 2-3 times, with obvious yield-increasing effects.
V. Harvesting and storage:
Around the Beginning of Winter, the onions have grown sufficiently and can be dug up. After digging, bundle them in 15 kg bundles and place them in a cool, ventilated place. Make 5-6 bundles per row, leaving a 50 cm passage between rows. If hot weather occurs, untie the bundles and dry them. During storage, they fear heat but not cold, and rainwater must be prevented.
VI. Main diseases and pests:
1. Leafminer: Mainly damages leaves. The larvae burrow into the skin and feed on the leaf mesophyll, leaving the epidermis as insect tunnels, which appear as white lines due to loss of green color.
2. Onion thrips: Mainly damages leaves, sucking the leaf mesophyll and forming white spots. In severe cases, the entire leaf appears gray-white due to loss of green color.
3. Onion maggot: Mainly damages the white stalk, stem disc, and roots underground, causing stem rot and leaf wilting, resulting in missing seedlings and broken rows.
4. Welsh onion purple blotch: Damages green leaves. The lesions start from small white spots and gradually expand to 3-5 cm, shaped like a spindle or jujube pit. The largest lesion can reach 6-7 cm in length, slightly sunken and dark purple, hence called purple blotch.
5. Welsh onion downy mildew: Diseased plants are twisted, deformed, and stunted, with relatively large yellow-white, oval lesions that look water-soaked, and the leaves droop and dry up.
6. Welsh onion rust: Commonly known as red anthracnose, it is a destructive disease in Welsh onion production areas. The lesions occur on the surface of tubular leaves and flower stalks. Initially round, oval, or spindle-shaped, upright along the direction of the leaf veins, dark yellow gradually changing to orange-brown, raised, scattered, and varying in spot size. Affected plants become yellow-wilted, dry up, and even lodging, causing reduced yield. The above cultivation experience is for reference only. Each region should manage according to local cultivation experience and climatic conditions.