Effects of Soil pH on Gaseous Nitrogen Loss Pathway via Feammox Process

• Main Authors: Ding Ma, Jin Wang, Jun Xue, Zhengbo Yue, Shaofeng Xia, Lei Song, Hongwen Gao
• Format: Article
• Language: English
• Published: MDPI AG 2021-09-01
• Series: Sustainability
• Subjects: Feammox; soil pH; acidification; N loss
• Online Access: https://www.mdpi.com/2071-1050/13/18/10393

The application of N fertilizer is one of the most critical soil acidification factors in China, and soil acidification significantly alters biogeochemical processes such as N loss. Anaerobic ammonium oxidation coupled with iron reduction (Feammox) is an important biological process for N loss in natural environments, with the end-products of N₂, NO₂⁻ and NO₃⁻. However, the response of Feammox pathways to soil pH fluctuation has not been thoroughly studied. In the current study, Feammox pathways and microbial communities were explored through a slurry culture experiment with an artificially adjusted pH combined with a ¹⁵N isotope tracing technique and molecular biotechnology. Results showed significant differences in the gaseous N loss through Feammox (0.42–0.97 mg N kg⁻¹ d⁻¹) under different pH conditions. The gaseous N loss pathways were significantly affected by the pH, and Feammox to N₂ was the predominant pathway in low-pH incubations. The proportion of N loss caused by Feammox coupled with denitrification increased as the soil pH increased. The gaseous N loss through Feammox increased by 43.9% when the soil pH decreased from 6.5 to 5.0. Fe-reducing bacteria, such as <i>Ochrobactrum</i>, <i>Sphingomonas</i>, and <i>Clostridium</i> increased significantly in lower pH incubations. Overall, this study demonstrated the effects of soil pH on Feammox pathways and extended the understanding of the N biogeochemical cycle in acidic soil.