Soil organic carbon saturation in cropland-grassland systems: Storage potential and soil quality

•Mineral-associated organic C deficits in croplands and grasslands were estimated.•The relationship between soil C-saturation and soil physical quality was assessed.•Challenges to the C-saturation concept and the SOC:clay ratio were highlighted.•C-saturation in grassland was positively linked to SOC accrual history.•SOC accrual is more beneficial for soil physical quality in croplands.