Soil organic carbon saturation in cropland-grassland systems: Storage potential and soil quality

Summary

This study evaluated soil organic carbon saturation in permanent grasslands and croplands across long-term monitoring sites in western Switzerland, developing a new empirical relationship between fine soil particles and mineral-associated organic matter carbon storage. Croplands showed substantially lower SOC saturation (62 ± 4%) with a deficit of −8.8 ± 1.2 mg C g⁻¹ relative to grassland reference sites, with saturation levels influenced by the proportion of temporary grassland in crop rotations. The findings suggest that many grasslands have not reached carbon saturation and may accumulate additional SOC under optimal management, informing both climate mitigation potential and soil quality co-benefits.

UK applicability

These findings are likely applicable to UK mixed farming systems, particularly in lowland areas with similar soil types and climates to western Switzerland. The methodology and saturation thresholds may require site-specific validation for UK conditions, but the demonstrated SOC deficit in croplands and potential for grassland-based carbon storage align with UK soil health and net-zero policy priorities.

Key measures

SOC saturation percentage; MAOMC (mineral-associated organic matter carbon) content; SOC:clay ratio; silt + clay particle content; C storage deficit (mg C g⁻¹ soil); proportion of temporary grassland in crop rotation

Outcomes reported

The study assessed soil organic carbon (SOC) saturation and physical soil quality in permanent grasslands and croplands using long-term monitoring sites in western Switzerland. It quantified mineral-associated organic matter carbon (MAOMC) saturation levels and SOC storage deficits in croplands relative to grasslands.

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