In order to explore the nitrogen in farmland water withdrawal process migration regularity,field experiment was conducted to analyze the content of TN,NH_4~+-N,NO_3~--N in soil as the depth of soil changed.The results showed that soil TN mainly distributed in 0~120 cm soil layer and migration quantity of TN below 120 cm soil layer was small.The content of NH_4~+-N mainly distributed in 0~40 cm soil layer,which was less affected under surface irrigation.The content of NO_3~--N mainly distributed in 0~60 cm s...