Mineral-Associated Organic Nitrogen Pool Size, Composition, and Accessibility Mediated by Agricultural Management and Soil Geochemical Characteristics

Author(s)

• Gabriella M. Griffen
• Andrew H. Whitaker
• Emma L. Bergh
• Marian Carrell
• Erik Knatvold
• Aniko Konya
• A. Stuart Grandy
• Andrea Jilling Ph.D., University of South CarolinaFollow
• Marco Keiluweit
• Rachel Hestrin

Document Type

Article

Abstract

Mineral-associated organic matter (MAOM) contains a substantial portion of soil nitrogen (N). MAOM-N could serve as an important N source for crops, but its availability and response to agricultural management across different soil types remains largely unknown. We characterized MAOM-N isolated from nine paired soils spanning a range of geochemical characteristics and maintained under two land uses—more intensively managed annual cropping systems or less intensively managed grasslands. On average, we found that MAOM contained approximately two-thirds of total soil N. Across all soil types, more intensive agricultural management resulted in a 50% decline in MAOM-N stocks, as well as a reduction in MAOM-N molecular diversity. Although clay content and extractable metals were positively correlated with MAOM-N stocks, none of the geochemical characteristics measured were strongly predictive of MAOM-N decline due to land use. This suggests that more intensive crop management limited the formation or caused the disruption of a broad suite of associations between a variety of soil minerals and organic N compounds. Under both agricultural land uses, approximately 20% of MAOM-N was mobilized through sequential extractions that may mimic conditions in the rhizosphere, suggesting that a significant portion of MAOM-N may be available to plants. Together, these findings help to quantify MAOM’s potential to supply crops with N across different soil types and agricultural systems. This can inform agricultural management recommendations and supports a growing understanding of MAOM as a dynamic N source and sink.

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.geoderma.2025.117627

Publication Info

Published in Geoderma, Volume 465, 2026.

Rights

© 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (https://doi.org/10.1016/j.geoderma.2025.117627).

APA Citation

Griffen, G. M., Whitaker, A. H., Bergh, E. L., Carrell, M., Knatvold, E., Konya, A., Grandy, A. S., Jilling, A., Keiluweit, M., & Hestrin, R. (2026). Mineral-associated organic nitrogen pool size, composition, and accessibility mediated by agricultural management and soil geochemical characteristics. Geoderma, 465, 117627.https://doi.org/10.1016/j.geoderma.2025.117627