Perennial grasslands are thought to sequester C, so restoring them is touted as part of the solution for mitigating climate change. Moreover, there is growing interest among managed grassland stakeholders in selling C credits on nascent C markets. Former agricultural and municipal sites are often considered viable areas for conversion to grasslands, with types ranging from unmanaged prairies with diverse plant communities to monocultures in highly managed urban environments. We sowed five perennial plant communities into an area that had undergone massive soil disturbance five years previous during conversion from row crop agriculture to C3 turf. We found that soils lost an average of 461 g C m-2 over the initial 3-y period, irrespective of mowing, fertilizer addition, or plant community type, with a similar magnitude of soil C loss occurring in the adjacent undisturbed turf. However, by the fourth year of sampling, soil C had returned to pre-treatment levels for most treatments. When sampled 14 years after disturbance and sowing, many soils had gained SOC relative to 2004 (~300 g C m-2). Exceptions included control-prairie grasses, fertilized-Kentucky bluegrass, mowed-fine fescue and mowed-prairie forbs, which had gained enough SOC to return to 2004 levels, but not enough for SOC gain in 2018. Soil-disturbing renovation or restoration of non-irrigated grasslands in the upper Midwest results in a short-term, but highly significant loss of soil C, but after 14 years SOC can sometimes, but not always recover and exceed pre-establishment SOC
