Abstract: Nitrogen is of vital important in crop growth.Nitrogen application amount was increased year by year,and the annual surplus of nitrogen in China was 3.60×10⁶-5.46×10⁶ t·a^-1.The nitrogen application affects not only crop growth,but also environment.Nitrate nitrogen and ammonium nitrogen in soil were observed by ion exchange resin membrane (IERM) in situ.The test results revealed the dynamic changes of nitrate nitrogen and ammonium nitrogen in soil,such as the migration,eluviation and transformation.The results are as follows:① The nutrient content of eluate of ion exchange resin membrane embedded in soil was similar to that obtained with the traditional test methods; ② Soil nitrate nitrogen was remarkably affected by cotton growth and nitrogen application.Nitrogen application could significantly improve the content of soil nitrate nitrogen,and a deficit of soil nitrate nitrogen occurred around 80 days after the emergence of cotton seedlings; ③ The content of soil ammonium nitrogen in cotton field under drip irrigation was low,its spatiotemporal change was complicated,and the reference value of the content of soil ammonium nitrogen for fertilization was low.

Key words: drip irrigation, cotton field, nitrate nitrogen, ammonium nitrogen, migration, ion exchange resin membrane