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Denitrification Rate and Controlling Factors for Accumulated Nitrate in the Deep Subsoil of Intensive Farmlands: A Case Study in the North China Plain

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  • H Yuan, Institute of Genetics and Developmental Biology Chinese Academy of Sciences, University of Chinese Academy of Sciences, Denmark
  • S Qin, Institute of Genetics and Developmental Biology Chinese Academy of Sciences, Denmark
  • W Dong, Institute of Genetics and Developmental Biology Chinese Academy of Sciences, Denmark
  • C Hu, Institute of Genetics and Developmental Biology Chinese Academy of Sciences, Denmark
  • Kiril Manevski
  • X Li, Institute of Genetics and Developmental Biology Chinese Academy of Sciences, Denmark
Subsoil denitrification is an important mechanism to reduce nitrate leaching into groundwater. However, regulating mechanisms of soil denitrification, especially those in the subsoil beneath the crop root zone, have not been well documented. In the current study, soil columns of 0-12 m depth were collected from intensive farming fields in the North China Plain (NCP). The fields had received long-term nitrogen (N) fertilizer inputs of 0 (N0), 200 (N200) and 600 (N600) kg N ha−1 year−1. Main soil properties related to denitrification, i.e. soil moisture, nitrate, dissolved organic carbon (DOC), soil organic carbon (SOC), pH, denitrifying enzyme activity (DEA), and anaerobic denitrification rate (ADR) were determined. Statistical comparisons among treatments were performed. The results showed that nitrate was heavily accumulated in the entire soil profile of the N600 treatment, compared to the N0 and N200 treatments. The SOC, DOC, and ADR decreased with increasing soil depth in all treatments, whereas considerable DEA was observed throughout the entire subsoil. The long-term fertilizer rates affected ADR only in the upper 4 m soil layers. The ADRs in the N200 and N600 treatments were significantly correlated with DOC. Combining with the multiple regression analysis, it was indicated that DOC rather than DEA was the key factor regulating denitrification beneath the root zone. Additional research is required to determine if the carbon addition into the subsoil can be a promising approach to enhance the nitrate denitrification in the subsoil and consequently to mitigate groundwater nitrate contamination in the intensive farming areas.
Original languageEnglish
JournalPedosphere
Volume29
Issue4
Pages (from-to)516-526
ISSN1002-0160
DOIs
Publication statusPublished - Aug 2019

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