Why do onions fork?

Why do onions fork? How should it be prevented? Please guide onions grown in many areas with 2 leaf sheaths and 2 bulbs growing in a bulb, commonly known as onion "fork" and "twins". This kind of product cannot be used for export, which seriously affects the value of the goods. First, the reason for forking onion bulbs is composed of leaf sheaths (outer) and scales (only leaf sheaths, no leaves, inside) at the base of the leaves. In the middle is the growth point of the main bud. There are dormant axillary buds at the bottom of the scales, which generally do not germinate. If the axillary buds germinate and become a separate bulb, it is a forked phenomenon. The main results are as follows: 1. When the seedlings are too large in North China from late October to early November in the first year, the suitable diameter of the seedling bulb is 0.3-0.8 cm. Due to the high temperature from October to November last year, the seedling bulb was too large, generally about 1 cm. Axillary buds germinated through vernalization stage, which not only occurred early bolting, but also easy to fork. 2. Warm winter and warm spring, the temperature was higher in winter last year, and the spring began earlier in spring, so that the growth period of onion seedlings was prolonged, the bulbs were too large, and the axillary buds forked through vernalization stage. 3. The plots covered with plastic film during planting are easy to fork because of the increase of ground temperature and the prolongation of growing period. 4. Too much nitrogen fertilizer in seedling stage too much nitrogen fertilizer in onion seedling stage, the growth of seedlings is too large, and it will also lead to forking. 5. In the seedling stage, the pests ate the main buds, causing more than 2 axillary buds to germinate. 6. when the burnt seedlings of chemical fertilizer are sprinkled with chemical fertilizer, the main buds are burned to death, resulting in axillary bud germination. 7. Seed problem using forked bulbs as seed bulbs has a certain heredity and is easy to fork after growth. Second, the technique of preventing hair forks. 1. when planting, remove the seedlings with a bulb diameter of more than 0.8 cm. 2. Fertilization in cultivated land should pay attention to the combined application of nitrogen, phosphorus and potassium, and avoid partial application of nitrogen fertilizer. 3. When mulching with plastic film, the smaller seedlings should be used properly. 4. 4000 times solution of 15% Anda suspension was sprayed in time at seedling stage to control beet armyworm and other pests. 5. When applying chemical fertilizer, you should be careful not to spread it into the leaf sheath. 6. make use of high-quality seeds. 7. For plants with forks found in spring, a knife made of bamboo can be used to root out one of the forks from the middle and keep one. During the growing period, 1/10000 solution of natural brassine Yishuofeng 481was sprayed 1-2 times to promote growth and development, and the plant could still grow into a normal bulb. 8. Plants that have been forked can still be put on the market if they are harvested early and don't wait for the phosphorus coat to break. Click to get more onion planting techniques click to get more vegetable planting techniques