(1.Yuxi Municipal Academy of Agricultural Sciences，Yuxi，Yunnan 653100；2.Yuxi Municipal Test Center for the Quality and Safety of Agricultural Products，Yuxi，Yunnan 653100)
According to the ordinary red-skinned onions with bulb separation in Jiangchuan County in Yuxi，taking rhizosphere soil and all organs of the onion as research subject，bulb separation and normal onion and their nutrient elements of rhizosphere soil were discussed through antitheses.The results showed that the typical characteristics such as onion separation，bulb separation appeared from the exterior and the concerned nutrient elements obviously after onions bulb separation.The P in all parts of bulb separation onion was apparently higher than that of the normal plants，while N and K in the bulb separation onions were less than the normal plants，so that P/N，P/K were high too，the proportions of N，P，K were uncoordinated，the absorbed doses of Ca，Mg，Zn were too high (mainly concentrating in bulbs and roots)，while low Mn content was an important factor for bulb separation.