Based on an approach that involved soil organic carbon (SOC) monitoring, radiocarbon measurement in bulk soil, and incubations from a long-term 60-year experiment, it was concluded that the avoidance of old carbon losses in the integrated crop–pasture systems is the main reason that explains their greater carbon storage capacities compared to continuous cropping. A better understanding of these processes is essential for making agronomic decisions to increase the carbon sequestration capacity.