SGER: Preferential and Stable Sorption of N- vs. C-rich Soil Organic Matter on Mineral Surfaces

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Despite the generally acknowledged importance of soil organic matter (SOM) to soil chemistry, soil hydrology, and soil structure, a detailed mechanistic understanding of the factors that influence SOM formation and stability has yet to emerge. The intellectual merit of this exploratory research effort lies in the examination and exploration of SOM formation and stability at the scale of the soil microaggregate. Specifically, using size-density-fractionation, radiocarbon dating of SOM, and nitrogen content determinations, the research will test a novel hypothesis that soil organic compounds nearest to mineral surfaces are the most stabilized, with stability decreasing with increasing distance of the organics from the mineral surfaces. A second hypothesis posits that soil organic compounds near mineral surfaces are especially nitrogen-rich, and that their nitrogen-containing components (amine groups) are responsible for their especially stable binding to mineral surfaces. There are many facets to the broader impacts of this research. Soil organic matter is critical to global well-being and security in that SOM supplies in large part the nitrogen, other nutrients, and soil structure needed to sustain agricultural and forest productivity. Changes in SOM formation and/or stability on a global scale may have consequences for atmospheric carbon dioxide concentrations and thus global climate. A better understanding of the mechanisms controlling SOM formation and loss will greatly improve our ability to efficiently manage SOM for commodity production and erosion control, and to mitigate soil carbon dioxide flux to the atmosphere.