关键词: 双季栽培, 氮肥施用量, 大白菜产量, 氮肥利用率, 大白菜硝酸盐含量, 土壤硝态氮累积

Abstract: The effects of Chinese cabbage N application rate on Chinese cabbage yields，nitrogen utilization，nitrate contents，and nitrate nitrogen accumulation in soil were studied under potato-Chinese cabbage double cropping system in Hetao irrigated area of Inner Mongolia with 5 N application rates at Chinese cabbage planting season．The results showed that the yields and the double cropping net economic returns were the highest with the Chinese cabbage N application rate of 120 kg•hm-2|the double cropping system N accumulation and N recovery ratio were enhanced at the total N application rate from 225 kg•hm-2 to 405 kg•hm-2，compared with that of the conventional mono potato production in the open field at the N application rate of 225 kg•hm-2|the nitrate contents in Chinese cabbage and the nitrate accumulations within 0-160 cm soil profiles were increased with the increscent N applied rates．At the  Chinese cabbage N application rate was≥120 kg•hm-2，the nitrate contents in Chinese cabbage reached a high level，and the nitrate accumulations within 0-160 cm soil profiles were≥162 kg•hm-2，hence the risk of nitrate contamination in underground water was increased for autumn irrigation．Reasonable N application rate had an effective effects on reducing nitrate contamination in groundwater，reducing nitrate content in Chinese cabbage，and increasing net economic return.

Key words: Double cropping cultivation, Nitrogen applcation rate, Chinese cabbage yield, Nitrogen utilization rate, Nitrate content in Chinese cabbage, Nitrate accumulation in soil