Sulfate as an Alternative Electron Acceptor: A Potential Strategy to Mitigate N2O Emissions in Upland Arable Soils

Abstract

Denitrification remains widely recognized as a significant contributor to N2O emissions in upland arable soils. This study evaluated metal sulfates (MSs) and zero-valent metals (ZVMs) as potential alternative electron acceptors (EAs) to reduce N2O emissions through microcosm experiments, functional gene analyses, microbial profiling, isotope mapping, and field-based manipulation experiments. ZVMs increased N2O emissions, whereas MSs significantly reduced them mainly by inhibiting denitrification rather than affecting nitrification. Isotopic mapping and NH4+ and NO3- concentration trends strongly supported these findings. Additionally, changes in microbial communities were noted, with a more general presence capable of using both NO3- and SO42-. SO42- could act as an EA alongside NO3- in anaerobic respiration, effectively reducing N2O emissions. Field experiments demonstrated the feasibility of MS applications, reducing yield-scaled N2O emissions by 7.6% to 21.5% compared to conventional practice without negatively impacting crop yields, highlighting the potential of SO42- materials as soil amendments in sustainable agriculture.