In addition to applying base fertilizer after planting, onions also require topdressing management. Onions have a high fertilizer requirement during their growth period, so topdressing is crucial. How should onions be topdressed? What are the methods for topdressing onions? After transplanting, onions initially grow their root system, then focus on above-ground growth. Only after the above-ground parts have fully developed does the bulb enlargement stage begin. Based on the growth and development characteristics of onions, timely topdressing is one of the keys to a high yield.
- Seedling Establishment Fertilizer: Apply seedling fertilizer 15-20 days after transplanting to replenish nutrients for continued root growth and prepare for the upcoming above-ground growth. Apply 5-6 kg of urea per acre and water to facilitate absorption and utilization.
- Growth Fertilizer: 30 days after transplanting, when onion vegetative growth intensifies, apply growth fertilizer to ensure the growth of functional leaves. The growth of the leaf vegetative tissue directly affects the size of the bulb; good leaf growth is the foundation for onion bulb development. Onion fertilization primarily uses nitrogen fertilizer, applying 5-6 kg of urea and 5 kg of potassium sulfate per acre.
- Bulb-enhancing fertilizer: After the plant has 8-10 tubular leaves and the bulbs begin to swell, a bulb-enhancing fertilizer should be applied. The key period for this fertilizer is the mid-stage of bulb enlargement. Excessive nitrogen fertilizer should be avoided in the early and later stages of bulb enlargement, as it can cause excessive vegetative growth and affect harvesting. It is recommended to apply 5-7 kg of urea and 8 kg of potassium sulfate per acre as the bulb-enhancing fertilizer. Potassium deficiency during the onion bulb enlargement period not only reduces yield but also affects the product's storage life.
