Carbon‐iron coupling reduced N2O emissions via promoting the conversion to N2 in paddy soils

Abstract

AbstractThe influence of redox reactions involving carbon‐iron coupling (organic carbon and iron oxides) on nitrous oxide (N2O) production in paddy soils remains poorly understood. In this study, two microcosm experiments were conducted to investigate the effects of carbon‐iron coupling on N2O emissions, and the underlying mechanisms were verified using quantitative denitrification functional genes (nirS, nirK, nosZI and nosZII) and high‐throughput sequencing. The results showed that ferrihydrite (iron) significantly promoted N2O‐N emissions (p < 0.05) after adding ammonium nitrogen, while glucose (carbon) significantly inhibited N2O‐N emissions (p < 0.05). Carbon‐iron coupling significantly decreased N2O‐N emissions (p < 0.05) but did not affect soil total nitrogen loss and increased nitrogen (N2) emissions. After adding high concentrations of acetylene (10% C2H2), the N2O‐N emissions from carbon‐iron coupling treatment increased significantly from 6.4 to 11.9 mg N kg−1 (p < 0.05), which confirmed that the carbon‐iron coupling reduced the N2O emissions by promoting the conversion of N2O to N2. The mechanisms behind carbon‐iron coupling promoting complete denitrification and reducing N2O emissions were attributed to glucose promoting iron reduction and carbon‐iron coupling enhancing the abundance of nosZI (42.7%) and nosZII (16.6%).