Long-term SOC stabilization in sandy subsoils – evidence from historical tillage experiments

Large SOC sequestration rates can be achieved by admixing C undersaturated subsoil into topsoil (e.g. by deep tillage), hence creating a strong disequilibrium in the C cycle of the local soil-plant-microbiome system. The magnitude of C sequestration (sum of SOC changes in top- and subsoil) strongly depends on the fate of SOC translocated into the subsoil. Here we present evidence for a strong preservation of subsoil SOC even after 40-60 years by re-analyses of historical field trials on sandy soils (Albic Luvisols, Arenic, Neocambic) in E Germany. Compared to Ap horizons (retain samples),  which were translocated into subsoil decades ago, 50-70% of former SOC is still detectable after 40-60years. From one field experiment (V210) a non-linear decline of SOC contents can be concluded (levelling off after 20y).