Spatiotemporal soil fertility responses to an enhanced rock weathering deployment within a temperate, agricultural watershed

Enhanced rock weathering (ERW) is a promising strategy for removing carbon dioxide from the atmosphere, yet field-scale observations suitable for evaluating ERW co-benefits related to soil-fertility improvements within temperate agriculture settings remain scarce. We conducted a 2.5-year investigation within a headwater catchment at the Sleepers River Research Watershed in Danville, Vermont, applying 20 t ha⁻¹ of finely milled, calcium-rich meta-basalt to near-stream pastures and adjacent, upslope hayfields. After establishing a year-long baseline, we continued to monitor topsoil chemical fertility indicators (pH, exchangeable essential nutrients, and cation exchange capacity) for 13 months following basalt application to evaluate changes relative to untreated control transects. The basalt amendment significantly raised soil pH by 0.15–0.24 units (p < 0.05) and increased exchangeable calcium by as much as 12%, with larger pH gains in soils that were initially more acidic. Other nutrients showed only modest responses, partly reflecting slow dissolution of metamorphic minerals rich in potassium and magnesium. Higher background variability in the pasture may have muted the detectable basalt-treatment signal, yet across the hillslope catena the magnitude of pH change scaled inversely with initial pH (lowest at the shoulder and foot), illustrating the role of land use and topographic position in modifying ERW responses. These results indicate that calcium-rich meta-basalt acts as a slow-release liming agent in well-buffered temperate soils and provide indications of the co-benefits of ERW to improving soil health within temperate agroecosystems.