Onion top dressing technology.
After the onion is planted, the root system first grows, and then it turns to the growth of the upper part of the ground. The growth of the upper part of the local area does not enter the growth period of bulb hypertrophy. According to the growth and development characteristics of onions, one of the keys to high yield of onions is to do a good job of applying fertilizer in stages.
Slow seedling fertilizer: 15 to 20 days after planting, the seedling fertilizer is slowed down to supplement nutrients for the continued growth of the root system and prepare for the growth of the above-ground parts that will soon begin. Urea 5-6 kg/mu, water after spreading to facilitate absorption and utilization.
Hair tree fertilizer: 30 days after planting, when vegetative growth is strengthened, hair tree fertilizer should be applied to ensure the growth of above-ground functional leaves. Because the size of the leaf vegetative body is very closely related to the size of the bulb in the future; the promotion of leaf growth in the early stage is to lay the foundation for the growth of the bulb in the later stage. Nitrogen fertilizer is mostly used, 5-6 kilograms of urea and 5 kilograms of potassium sulfate per mu.
Head fertilizer: The bulb begins to swell after the plant has 8 to 10 tubular leaves. You should chase the head fertilizer once. The head fertilizer should focus on the middle stage of the bulb swelling growth. Do not apply too much nitrogen fertilizer when the bulb is just beginning to grow. In the later stage of bulb expansion, if excessive nitrogen fertilizer is applied, "greed-green" will occur and affect harvesting. Apply 5-7 kilograms of urea and 8 kilograms of potassium sulfate per mu. During the bulb growth period, potassium deficiency will not only reduce the yield, but also have a certain impact on the storability of the product.