Effects of N Applied Rates on Movement of Soil NO_3~-N and Quality of Chinese Onion

The effects of different nitrogen rates on soil nitrate nitrogen and onions'quality was studied in Chinese onion/wheat rotation system in Zhangqiu county,Shandong Province,and the N supplying target value on Chinese onion was determined.The results showed that soil NO 3-N leaching was serious in Chinese onion soil of Zhangqiu.The content of soil NO 3-N has very significant difference between T5 and T1 in different growth periods.At harvest time,the residue of soil NO 3-N in the three arable layer of T5 were 4.35 mg kg,6.81 mg kg and 6.49 mg kg,respectively.These data indicated that the nitrogen rate was more than Chinese onion needs in treatment T5.The yield of T4 was higher than other treatments compared with T5.And,the NO 3-N in Chinese onion was very significant differences between T4 and T5.Vc and soluble sugar contents decreased with amount of applied nitrogen increased.