Roots are key to increasing the mean residence time of organic carbon entering temperate agricultural soils

The ratio of soil organic carbon stock (SOC) to annual input gives an estimate the mean residence time that enters (MRTOC). It indicates how efficiently biomass can be transformed into SOC, which is particular relevance for mitigating climate change by means SOC storage. There have been few comprehensive studies MRTOC and their drivers, these mainly restricted global scale, on climatic drivers dominate. This study used unique combination regional-scale cropland grassland topsoil (0–30 cm) data average site-specific OC derived from German Agricultural Soil Inventory elucidate main MRTOC. Explanatory variables related composition other soil-forming factors were explain variability in a machine-learning approach. On average, entering agricultural topsoils had MRT 21.5 ± 11.6 years, with grasslands (29.0 11.2 n = 465) having significantly higher than croplands (19.4 10.7, 1635). was explained proportion root-derived inputs soils, most important variable explaining at regional scale. properties such as clay content, group, C:N groundwater level also important, indicating driven site composition. However, great importance indicated actively managed, maximization root being straightforward extend assimilated C remains consequently increase stocks.