Abstract

The impact of prescribed sheep grazing on soil organic carbon (SOC) was investigated by comparing a 2-acre grazed and a 2-acre non-grazed (control) portion of redeveloped land previously seeded with pasture mix in Southwest Michigan. This study aimed to measure changes in SOC resulting from prescribed sheep grazing by examining two key soil organic matter (SOM) fractions: particulate organic matter (POM) and mineral-associated organic matter (MAOM) along with soil physical and chemical properties (e.g., bulk density, infiltration rate, moisture content, pH, conductivity). Soil cores were collected from 5 locations within each of the 2-acre plots using a diagonal random sampling method over one grazing season starting in Spring 2024. Soil cores were collected to a depth of 24 inches and spilt into 4 6-inch segments for separation by size into POM (53 – 2000 µm) and MAOM (<53>µm) fractions following chemical dispersion and subsequent carbon and nitrogen elemental analysis. Preliminary field observations and surveys showed notable ecological differences between the control and grazed sites in vegetation type, drainage differences, and wildlife habitat. Preliminary results reveal lower bulk density and improved infiltration in the grazed site compared to the non-grazed site and higher POM mass in the upper 0-6 inches in some parts of the control site verses the grazed site. These early results suggest that prescribed grazing may influence not only storage in different SOC fractions but also depth of soil carbon storage on a short temporal scale (months). Other benefits include broader ecological parameters that support sustainable native habitats with the potential for providing greenhouse gas offsets if increases in deeper SOC fractions are maintained. Continued research and systematic monitoring are ongoing to confirm the preliminary results and observations.