In order to investigate the nitrogen removal performance and how it response to low carbon-to-nitrogen in eco-ditch and wetland system under controlled irrigation and drainage. Based on field experiment data, the changes of nitrogen concentration and carbon-to-nitrogen in the eco-ditch and wetland system were monitored. Results showed that TN、NH4+-N and NO3-_N concentration in drainage were peaking after fertilization and then were significantly reduced after retaining in the eco-ditch. The eco-ditch obtained 63.9% TN, 67.8% NH4+-N and 83.2% NO3-_N removal. Nitrogen concentration reduced further after purification in wetland, with the average removal rate of 47.7%、44.3% and 82.0% for TN, NH4+-N and NO3-_N. The influence of organic matter in the system on water quality is little, the carbon-to-nitrogen ratio maintained low. The eco-ditch and wetland system under controlled irrigation and drainage are effective in removing nitrogen in paddy field drainage, and the influence of low carbon-to-nitrogen on nitrogen removal efficiencies is little.
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