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| DOI：10.13522/j.cnki.ggps.2017.0172 |
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| Numerical Simulation of Nitrogen Loss in Surface Runoff and Leaching from Paddy Field |
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YANG Rui, TONG Juxiu, LI Jiayun, WEI Wenshuo
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Key Laboratory of Groundwater Cycle and Environment Evolution(China University of Geosciences), Ministry of Education, Beijing 100083, China; Collage of Water Resources and Environment Sciences, China University of Geosciences, Beijing 100083, China
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| 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 simulation 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 concentrations in runoff during the decline stage on the day of fertilization were fitted well by power function. The nitrate concentration in runoff on the 18th day after fertilization was also well fitted by power function. While the total N and ammonium concentrations in runoff on the 18th day after fertilization were fitted well by exponential function. During the early half runoff N loss processes, the relationship between cumulative surface runoff and accumulation of N loss was fitted well by parabolic function. In the late half process, the parabolic function was slightly 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. |
| Key words: nitrogen; paddy field; runoff loss; soil profile; numerical simulation |
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