Surface soil organic carbon sequestration under post agricultural grasslands offset by net loss at depth

Post agricultural grasslands are thought to accumulate soil organic carbon (SOC) after cultivation cessation. The Conservation Reserve Program (CRP) in the U.S. is a wide-scale, covering approximately 8.9 Mha as of 2020, example row-crop grassland conversion. To date, changes SOC stock CRP lands have mostly been evaluated at local scales and focused on surface 20–30 cm profile. Thus, we lack knowledge dynamics continental scale, especially subsurface soil, Rapid Carbon Assessment (RaCA) project most recent effort by United States Department Agriculture (USDA) systematically quantify C 0–100 profile across conterminous US. Here analyzed data from RaCA evaluate stocks both scale. We found there was no difference between croplands when comparing profiles, which indicates that sequestration insignificant overall. did find higher (0–5 cm). However, such levels cm) were offset lower (30–100 CRP. also humid warm regions may net because they much more compared with same regions. Whether caused legacy effects or result losses needs be verified long-term repeated sampling soil. This analysis highlights importance examining cessation accurately measure improve rates lands.