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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #414141
Research Project: Developing Aspirational Practices Through Improved Process Understanding to Protect Soil and Air Resources and Increase Agricultural Productivity in the Upper Midwest U.S.

Location: Soil and Water Management Research

Title: Isotope partitioning of nitrous oxide emissions from the US corn belt

Author
item GRIFFIS, TIMOTHY - University Of Minnesota
item YU, ZHONGJIE - University Of Illinois
item Baker, John
item MILLET, DYLAN - University Of Minnesota

Submitted to: Geophysical Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2024
Publication Date: 11/16/2024
Citation: Griffis, T.J., Yu, Z., Baker, J.M., Millet, D.B. 2024. Isotope partitioning of nitrous oxide emissions from the US corn belt. Geophysical Research Letters. 51(1). Article e2024GL109623. https://doi.org/10.1029/2024GL109623.
DOI: https://doi.org/10.1029/2024GL109623

Interpretive Summary: Increasing use of synthetic nitrogen fertilizers for agricultural production is causing higher atmospheric nitrous oxide (N2O) concentrations. Nitrous oxide is a long-lived greenhouse gas and degrades the protective stratospheric ozone layer. Using tall tower N2O isotope observations from within the US Corn Belt, we examine how different processes (denitrification vs nitrification) and sources (corn fields vs wetlands, rivers, and streams) contribute to variations in atmospheric N2O. The findings indicate that a substantial amount of nitrogen leakage from agricultural crops contributes to N2O emissions via indirect sources such as drainage networks. These findings can help inform mitigation strategies targeting nitrogen use and leakage pathways from agricultural systems.

Technical Abstract: Agriculture is the dominant source of anthropogenic nitrous oxide (N2O) –a greenhouse gas and a stratospheric ozone depleting substance. The US Corn Belt is a large global N2O source, but there remain large uncertainties regarding its source attribution and biogeochemical pathways. Here, we interpret high frequency stable N2O isotope observations from a very tall tower to improve our understanding of regional source attribution. We detected significant seasonal variability in d15Nbulk and the isotope site preference (d15NSP =_ _d15Na _– _d15Nß) indicating a predominance of denitrification during the growing period but of nitrification during the snowmelt period. Isotope mixing models and atmospheric inversions both indicate that indirect emissions contribute substantially (>35%) to total N2O emissions. These independent constraints on regional N2O emissions provide compelling evidence that disparities observed between top-down versus bottom-up emission budgets are associated with limitations in quantifying and upscaling indirect emissions.