Physical Protection of Soil Carbon Stocks Under Regenerative Agriculture

Abstract. Regenerative agriculture is emerging as a strategy for carbon sequestration and climate change mitigation. However, for sequestration efforts to be successful, long-term stabilisation of Soil Organic Carbon (SOC) is needed. This can be achieved either through the uplift in recalcitrant carbon stocks, and/or through physical protection and occlusion of carbon within stable soil aggregates. In this research, soils from blackcurrant fields under regenerative management (0 to 7 years) were analysed with respect to: soil bulk density (SBD), aggregate fractionation (water stable aggregates vs. non-water stable aggregates (WSA and NWSA respectively)), soil carbon content, and carbon stability (recalcitrant vs. labile carbon). From this, long term carbon sequestration potential was calculated from both recalcitrant and physically occluded carbon stocks (stabilised carbon). Results indicated favourable shifts in the proportion of NWSA:WSA with time. This ratio increasing from 27.6 % : 5.8 % (control soil) to 12.6 % : 16.0 % (alley soil), and 16.1 % : 14.4 % (bush soil) after 7 years. While no significant (p ≥ 0.05)) changes in recalcitrant carbon stocks were observed after 7 years, labile carbon stocks increased significantly (p ≤ 0.05) from 10.44 t C ha^-1 to 13.87 t C ha^-1. As a result, total sequesterable carbon (stabilised carbon) increased by 1.7 t C ha^-1 over the 7 year period, due to the occlusion and protection of this labile carbon stock within WSA fraction. This research provides valuable insights into the mechanisms of soil carbon stabilisation under regenerative agriculture practices and highlights the importance of soil aggregates in physically protecting carbon net-gains.