Total organic carbon and its correlation with other soil health indicators in integrated crop-livestock-forest systems

Total organic carbon (TOC) is a key indicator of soil health, playing a crucial role in carbon sequestration and ecosystem services. In integrated crop-livestock-forest systems, TOC dynamics result from complex interactions between land-use practices and soil properties. However, the relationships between TOC and other soil health indicators in integrated crop-livestock-forest systems remain unclear. Understanding these correlations is important for improving soil management strategies in sustainable agriculture. This study assessed TOC content and its correlation with soil health indicators across different land-use systems in a Brazilian Ferralsol in São Carlos - SP. The evaluated systems included continuous grazing (CONT), rotational grazing (ROT), integrated crop-livestock (ICL), integrated livestock-forest (ILF), and integrated crop-livestock-forest (ICLF). Soil samples were collected from 0–10, 10–20, 20–40, and 80–100 cm depth layers. TOC was measured via dry combustion using an elemental CN analyzer. Spearman correlation analysis was used to assess relationships between TOC and other soil health indicators. In the 0-10 cm depth, TOC was highest in ICLF (2.38%) and the lowest in CONT (1.95%), while intermediate values were found for ROT (2.13%), ICL (2.10%), and ILF (2.07%). TOC consistently declined with depth, ranging from 1.33% to 1.74% at 10–20 cm, 1.09% to 1.18% at 20–40 cm, and 0.61% to 0.70% at 80–100 cm, with no significant differences between grazing systems in these layers. A moderate correlation was found between TOC and the mean weight diameter of soil aggregates (0.43), while strong correlations were observed between TOC and both soil microporosity (0.63) and pore connectivity (0.60). These findings indicate that TOC is closely linked to soil porosity and aggregate stability, supporting its role as a key soil health indicator. This study highlights the potential of integrated systems to enhance TOC sequestration and improve overall soil health. The results contribute to many Sustainable Development Goals (SDG), particularly SDG 15, Life on Land, by supporting sustainable land-use practices that enhance ecosystem services and climate resilience in agriculture. This work was supported by São Paulo Research Foundation (Fapesp, grants 2019/14144-0, 2023/02444-5 and 2025/01213-5).