Numerical Simulation of Nitrogen Loss in Surface Runoff and Leaching from Paddy Field

YANG Rui; TONG Juxiu; LI Jiayun; WEI Wenshuo

doi:10.13522/j.cnki.ggps.2017.0172

Abstract：[Objective]Field experiments were conducted in a paddy field under traditional continuously flooded irrigation(CFI)to study nitrogen(N)loss by runoff and leaching from soil profile.[Method]The numerical sim-ulation of runoff N loss was carried out,and the distributions of N concentration in soil profile before and after fertilization were also analyzed.[Result]The reaults showed that,the total N,ammonium and nitrate concentra-tions in runoff during the decline stage on the day of fertilization were fitted well by power function.The nitrate concentration in runoff on the 18thday after fertilization was also well fitted by power function.While the total N and ammonium concentrations in runoff on the 18thday after fertilization were fitted well by exponential func-tion.During the early half runoff N loss processes,the relationship between cumulative surface runoff and accu-mulation of N loss was fitted well by parabolic function.In the late half process,the parabolic function was slight-ly better than the logarithmic function.NO3--N content was low and NH4+-N was the main N loss under CFI in the paddy field.The N concentration in upper soil(0~30 cm)was usually greater than that in lower soil.And the change amplitude in upper soil was much higher than that in subsoil.[Conclusion]The process of runoff N loss in paddy field can be quantitatively described by elementary function fitting.Increasing the utilization rate of N in the upper soil by root is beneficial to reduce the leaching,and the upper soil area with high degree of N content is the key and difficult point of the leaching process quantitative description.