Adaptive multi-paddock grazing enhances soil carbon and nitrogen stocks and stabilization through mineral association in southeastern U.S. grazing lands

Authors: MOISER, SAMANTHA - COLORADO STATE UNIVERSITY; APFELBAUM, STEVEN - APPLIED ECOLOGICAL SERVICES, INC.; BYCK, PETER - ARIZONA STATE UNIVERSITY; CALDERON, FRANCISCO; TEAGUE, RICHARD - TEXAS A&M UNIVERSITY; THOMPSON, RY - APPLIED ECOLOGICAL SERVICES, INC.; COTRUFO, M - COLORADO STATE UNIVERSITY

Submitted to: Journal of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2021
Publication Date: 6/15/2021
Citation: Moiser, S., Apfelbaum, S., Byck, P., Calderon, F.J., Teague, R., Thompson, R., Cotrufo, M.F. 2021. Adaptive multi-paddock grazing enhances soil carbon and nitrogen stocks and stabilization through mineral association in southeastern U.S. grazing lands. Journal of Environmental Management. 288. Article e112409. https://doi.org/10.1016/j.jenvman.2021.112409.
DOI: https://doi.org/10.1016/j.jenvman.2021.112409

Interpretive Summary: Grassland soils are at risk of losing soil organic matter when they are subject to continuous grazing. Rotational grazing is a system in which animals are moved routinely to avoid overgrazing, allowing for healthy grass regrowth. This work shows how rotational grazing has several benefits on soil quality over conventional grazing. Rotational grazing can increase soil organic matter and conserve soil nitrogen. In addition, the increased soil carbon that accumulates in the rotationally grazed soils is associated to soil minerals in a way that increases the long term stability of soil organic matter.

Technical Abstract: Grassland soils are a large reservoir of soil carbon (C) at risk of loss due to conventional continuous grazing. By promoting regenerative grazing management practices that improve soil C sequestration and soil health, grasslands have the potential to help alleviate rising atmospheric CO2 as well as sustain grass productivity across a vast area of land. Previous research has shown that rotational, specifically adaptive multi-paddock (AMP), grazing can increase soil C stocks in grasslands systems, but the extent and mechanisms are unknown. We conducted a large-scale on farm study on five “across the fence” pairs of AMP and continuous grazing grassland covering the full spectrum of southeast United States grazing lands. We quantified soil C and N stocks, their isotopic and Fourier-transform infrared spectroscopy signatures as well as their distribution among soil organic matter (SOM) physical pools characterized by contrasting mechanisms of formation and persistence in soils. Our findings show that the AMP grazing sites had over 13% more soil C and 9% more soil nitrogen (N) compared to the continuous grazing sites. Adoption of AMP grazing lead to an increase in the soil of 9 Mg C ha-1 and 1 Mg N ha-1 over 1 meter depth relative to conventional grazing. Additionally, the increase was mostly in the mineral associated organic matter fraction, suggesting long-term persistence of the accrued C on AMP grazing farms. The higher N stocks and lower 15N signature of AMP soils also point to higher N retention in these systems. These findings provide evidence that AMP grazing is a powerful management strategy to sequester C in soil and retain N in the system, thus contributing to climate change mitigation.