Insights from a Two-Year Field Trial of Enhanced Weathering with basalt on alpine grassland: Soil, Water, and Biomass Responses

Enhanced weathering is under active consideration as a permanent carbon dioxide removal pathway, but its agronomic and biogeochemical outcomes remain insufficiently constrained under field conditions. We report a two-year field trial with four treatments: (i) basalt, (ii) control, (iii) manure, and (iv) basalt + manure, conducted on grassland in the Austrian Alps.

Soil water was sampled continuously at 40 cm depth using suction plates to capture high‑resolution dynamics in pH, alkalinity, and dissolved ion composition. Soil measurements were conducted at the start and end of the experiment. Nutritional quality of forage was analyzed after each cut. The aim of the experiment was to quantify CO₂ drawdown from weathering and potential agronomic benefits in the context of typical regional farming practice.

Basalt addition did not lead to a detectable increase in alkalinity in soil water over the study period, highlighting the slow dissolution rates under temperate field conditions. However, basalt application resulted in a measurable increase in biomass production compared to the control, suggesting potential agronomic co-benefits.

We present further observed geochemical and biological responses and discuss implications for monitoring, verification, and the design of future trials.