A large nitrogen supply from the stable mineral-associated soil organic matter fraction

Soil organic matter (SOM) mineralization and nitrogen (N) release are key biogeochemical processes for which the relative contribution of particulate (POM) and mineral-associated organic matter (MAOM) fractions is poorly understood. MAOM is generally considered to be a more stable fraction that cont...

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Bibliographic Details
Published in:Biology and fertility of soils 2023-10, Vol.59 (7), p.833-841
Main Authors: Villarino, Sebastián H., Talab, Emir, Contisciani, Luciano, Videla, Cecilia, Di Geronimo, Paula, Mastrángelo, Matias E., Georgiou, Katerina, Jackson, Robert B., Piñeiro, Gervasio
Format: Article
Language:English
Subjects:
Agricultural land
Agriculture
Biomedical and Life Sciences
carbon
Carbon-nitrogen ratio
clay fraction
Clay minerals
Concentration gradient
Continuous grazing
Environmental gradient
forests
Grazing
Land use
Life Sciences
Mineralization
Nitrogen
Organic matter
Organic soils
Original Paper
Pasture
Pasture management
pastures
Soil
Soil organic matter
soil organic nitrogen
Soil Science & Conservation
Soils
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Summary:Soil organic matter (SOM) mineralization and nitrogen (N) release are key biogeochemical processes for which the relative contribution of particulate (POM) and mineral-associated organic matter (MAOM) fractions is poorly understood. MAOM is generally considered to be a more stable fraction that contains most of the soil organic N, whereas POM is more readily decomposable and contains less N. Here, we measured variations in the potentially mineralizable N from each SOM fraction across three contrasting land-uses (forest, pasture, and croplands) and two different grazing managements (rotational and continuous grazing). Contrary to expectations, we found that the MAOM fraction consistently supplied more N than the POM fraction during SOM mineralization in all land-uses evaluated. Across our environmental gradient, potentially mineralizable N from POM increased with the carbon (C) concentration and C/N ratio of POM, while potentially mineralizable N from MAOM increased with the C concentration of MAOM but decreased with clay content. Our work suggests that MAOM contributions to short-term N mineralization and N supply to plants have been undervalued.
ISSN:0178-2762
1432-0789
DOI:10.1007/s00374-023-01755-z