Organic carbon sequestration potential of Slovenian agricultural soil and the impact of management practices on SOC stock

Improving soil management is crucial for mitigating climate change by increasing soil organic carbon (SOC). This study addresses the question of whether Slovenian agricultural soils can increase SOC stocks and achieve the 4per1000 initiative (4p1000.org). We calculated the SOC stocks, soil carbon sequestration (SCS) potential of the fine soil fraction (<20 µm) (C_sd) and the SCS potential of bulk soil for different agricultural uses in Slovenia. In addition, we conducted agricultural land management scenarios to determine a possible increase in SOC stocks. The results showed an average SOC stock of 94.7 t ha⁻¹ in the agricultural soils of Slovenia. High C_sd values were mainly found in croplands, intensive orchards and vineyards. The C_sd (0–30 cm) amounts to 16.3 Mt SOC for the entire country. In addition, our results on SCS potential were compared with similar assessments from other European countries, where the range of bulk soil SCS potential was between 0.03 and 2.8‰ SOC change yr⁻¹. With the current management of agricultural land in Slovenia, the SCS is almost balanced (+0.1‰). Different management scenarios showed that efficient fertilizer use, no-till, vegetation cover with biodiverse crop rotation and keeping residues on the surface lead to a significant SOC stock increase by 19.6 t ha⁻¹ in 20 years, which supports the 4per1000 initiative target (10.5‰).