Landscape dependent changes in soil properties due to long-term cultivation and subsequent conversion to native grass agriculture

On farmland in undulating landscapes, soil organic carbon (SOC) stocks depend on landscape position. In the North American Prairie Pothole region, we compared a native prairie reference site with a nearby farm undergoing transition to perennial agriculture (“restoration”) after a century of producing annual crops. We quantified legacy effects of farming at four upland landscape positions (to 0.9-m soil depth) and three wetland positions (to 1.0-m soil depth). We also quantified short-term (4years) changes in SOC stocks (to 0.15-m soil depth) during restoration, and how these changes were impacted by historic erosion. Surface (to 0.05-m soil depth) measurements indicated degradation of the cropland soil relative to the prairie at all landscape positions due to less soil organic matter (SOM) and altered soil properties (e.g., water aggregate stability and microbial activity). All upland and wetland positions of the farm lost SOC stocks (Mgha−1) relative to the prairie in the top 1.5 Ggha−1 of soil (~14-cm depth). However, when considering a larger mass of soil, 4.5Ggha−1 (~39-cm depth), loss of SOC stocks was significant (p