Soil carbon persistence in integrated agricultural systems

Soil organic carbon (SOC) persistence is a key component of climate regulation, yet its stabilization mechanisms under integrated agricultural systems (IAS) remain poorly understood. This study aimed to assess whether IAS increase SOC persistence compared to perennial pasture (PA) across a gradient of soil textures. Soil samples were collected from four sites in Brazil, representing clay contents of 8%, 14%, 20%, and 40%, at a depth of 0–30 cm. The study evaluated integrated agricultural systems, including crop–livestock (CLI) and crop–livestock–forest (CLFI) configurations. For comparison, PA and native vegetation (NV) were included as reference systems. SOC was fractionated into particulate organic carbon (POC, >53 μm) and mineral-associated organic carbon (MAOC, <53 μm) by wet sieving after chemical dispersion, and carbon contents were determined through elemental analysis. Across all textures, IAS exhibited significantly lower POC and MAOC concentrations compared to PA and NV. For instance, in soils with 40% clay, PA contained 25.9 g C kg⁻¹ in the POC fraction, significantly exceeding levels in CLI (15.5 g C kg⁻¹) and CLFI (11.0 g C kg⁻¹) (p < 0.001). Similarly, in soils with 20% clay, POC content in PA exceeded that in CLI by 14.28 g C kg⁻¹. Soils with 14% clay followed the same trend, with PA consistently presenting higher values for both fractions. In the sandiest soils (8% clay), NV showed the highest MAOC content (5.84 g C kg⁻¹), while IAS presented the lowest (3.70 g C kg⁻¹), highlighting the limited potential for SOC stabilization in such environments. These findings indicate that IAS may not enhance SOC persistence relative to well-managed perennial pastures, likely due to frequent biomass removal, increased soil disturbance, and reduced aggregate stability, as evidenced by lower weighted mean diameter of soil aggregates. The consistently lower MAOC concentrations suggest limited formation of stable organo-mineral associations, particularly in low-clay soils where carbon is more susceptible to loss. Despite their multifunctional appeal, IAS may offer limited long-term benefits for carbon sequestration unless management practices are adapted to increase organic matter inputs and reduce disturbance. This study underscores the importance of soil texture-informed strategies to improve SOC stabilization in managed systems and contributes to Sustainable Development Goals (SDGs) 13 (Climate Action) and 15 (Life on Land), reinforcing the need for site-specific approaches to climate-resilient agriculture.