Enhanced rock weathering changes cropland soil physical properties and carbon dioxide emissions

Crushed silicate rock amendments are being added to croplands as an enhanced rock weathering (ERW) strategy for carbon dioxide removal, but field results remain difficult to interpret. In agricultural soils, CO₂ concentrations and fluxes vary rapidly with soil moisture and pore structure, complicating evaluation of ERW performance.

To address this challenge, researchers conducted a basalt-amended soybean field experiment in Hokkaido, Japan, combining continuous soil CO₂ sensor observations with measurements of soil physical properties related to water and gas movement. Basalt incorporation (150 t ha⁻¹) compacted surface soils and increased water retention while the relationship between air content and gas diffusivity remained largely unchanged, suggesting that the soil’s main air-conducting pore network was preserved.

The team then used depth-resolved CO₂ concentration profiles together with gas diffusivity estimates to calculate CO₂ fluxes and to capture rainfall-driven carbon dioxide pulses. Continuous CO₂ sensing revealed transient, depth-specific concentration changes associated with soil moisture dynamics. Under basalt application, CO₂ fluxes also tended to be higher.

This approach highlights how integrating continuous CO₂ sensing with soil physical measurements provides a richer and more reliable picture of field-based assessments of ERW performance.