Journal Article

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

Piñeiro, Gervasio, Villarino, Sebastián H., Georgiou, Katerina, Mastrángelo, Matias E., Videla, Cecilia, Contisciani, Luciano, Di Geronimo, Paula, Jackson, Robert B., Talab, Emir

2023

Overview

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.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V
• Subject: 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 / Original Paper / Pasture / Pasture management / pastures / Soil / Soil organic matter / soil organic nitrogen / Soil Science & Conservation / Soils