Preliminary assessment of crushed rock, compost, and biochar amendments on soil physical properties

Abstract

Innovative carbon dioxide removal strategies using soil amendments like crushed silicate rock may alter soil structure and function by inducing changes in soil mineralogy. We hypothesized that crushed silicate rock would improve soil physical properties. This study investigated how stand-alone and combined application of crushed metabasalt and olivine rock (40.3 and 26.9 Mg ha⁻¹), compost (9 Mg ha⁻¹), and biochar (10 Mg ha⁻¹) influenced soil physical health over a 2-year drought period in a Northern California corn (Zea mays L.) cropping system. Rock-amended soils exhibited greater aggregate stability, up to 400% greater hydraulic conductivity, and up to 21% lower penetration resistance following 3 years of repeated application, with no changes in texture or plant-available water. Co-application of organic amendments yielded no additional benefits compared to rock alone, but usually improved physical properties compared to the unamended control. Long-term studies are needed to gauge the rate and persistence of these improvements.

Core Ideas

• Enhanced rock weathering harnesses weathering reactions to remove atmospheric carbon dioxide via soil and water.
• The impacts of crushed silicate rock amendments on soil physical properties over time remain unclear.
• Rock-amended soils showed evidence of structural and hydraulic improvement following three annual applications.
• Biochar enhanced soil physical quality alone and in combination with compost.
• Future work should assess co-benefits and tradeoffs associated with silicate rock application on cropland soils.