Deep soil inventories reveal that impacts of cover crops and compost on soil carbon sequestration differ in surface and subsurface soils

Summary

This study utilised deep soil inventories to assess the impacts of cover crops and compost applications on soil carbon sequestration across surface and subsurface soil horizons, drawing on long-term field trial data likely from the UC Davis Agricultural Sustainability Institute. The findings suggest that conventional surface measurements (0–30 cm) may underestimate or misrepresent the full carbon sequestration potential of organic management practices, as subsurface responses can differ markedly in magnitude and direction. The paper contributes to growing evidence that deep soil sampling is essential for accurately quantifying carbon stocks and evaluating the climate mitigation potential of regenerative agricultural practices.

UK applicability

The study is based in California, USA, and the specific cropping systems and soil types may not translate directly to UK conditions; however, the methodological finding that subsurface carbon responses differ from surface responses is highly relevant to UK soil carbon monitoring frameworks and the design of agri-environment schemes under the Environmental Land Management programme.

Key measures

Soil organic carbon (SOC) stocks (Mg C/ha) at multiple soil depths; bulk density; deep soil core inventories to at least 1 m depth; treatment comparisons across cover crop and compost inputs

Outcomes reported

The study measured soil organic carbon stocks at multiple depths (including subsoil horizons beyond 30 cm) under different management treatments including cover crops and compost amendments. It reported how carbon sequestration responses differ between surface and subsurface soil layers across farming systems.

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