(1) Breeding Single heart rate breeding can fundamentally reduce the occurrence of twins and multiple births. Promote early nursery, early transplantation, but also can prevent the formation of twins, multiple births onion later. (2) Pay attention to the late expansion of water and fertilizer management bulbs, pay attention to the balanced supply of water and fertilizer, reduce nitrogen fertilizer, increase potassium fertilizer, late on-line use of onion greed and greenery, and increase the probability of forming twins, especially nitrogen fertilizer to promote lateral bud growth, easy to produce double Heart ball. Irrigation should be stopped 10 days before onion harvest to facilitate the natural dry shell onion and increase the storage stability. (3) Pest control Pest control insects and other pests ingest onion leaves and inject harmful saliva, resulting in onion growth mechanism disorders, causing sprouts in dormant buds and new leaves, the new leaves of the accumulation of nutrients to small bulbs, small The expansion of the bulb causes the entire bulb to expand. If the bulb differentiates early or the whole plant grows in a superior condition, the bulb which continues to expand will eventually burst through the bulb scales that enclose it and become independent plants, thereby reducing commerciality. Underground pest mites and ground tigers can damage onion roots, causing slow growth, stagnation, and even death of plants. Because the plants that are damaged are reduced or stopped, water and fertilizer are captured, creating favorable conditions for the growth and development of neighboring plants, resulting in the growth of lush bulbs. Being too large increases the chance of twins and multiple births. If the field pests are serious, the size of onion bulbs not only affects the yield, but also affects the commodity rate. Therefore, pests and diseases should be prevented and treated in time. (4) Timely prevention of extremely high temperatures and drought hazards The suitable growth temperature for long-term bulb growth to bulb expansion is 15°C to 27°C. If the temperature exceeds 27°C for several days, the growth of onions will be detrimental. Continued drought, extreme high temperatures inhibit the normal growth of onions, stimulate the growth of lateral buds, easy to form twins, and more cells; therefore timely, timely light irrigation, ground irrigation to prevent the heat and drought hazards. (5) Drying after harvesting to reduce the humidity in the storage tank to increase the drying period after harvesting on the onion head for several days to reduce the humidity in the storage tank is an important measure to increase the storage period. Manual Breast Pump,Massage Breast Pump,Led Display Breast Pump,Manual Massage Breast Pump NINGBO YOUHE MOTHER&BABY PRODUCTS CO.,LTD , https://www.youha.com