[A-GE34] Subsurface Mass Transport and Environmental Assessment

[AGE34-03] Impact of Enhanced Rock Weathering on Soil CO₂ Dynamics: A Two-Year Field Monitoring Study in Farmland in Hokkaido

*Zhu Yan¹, Hiroshi Uchibayashi¹, Takuro Shirano², Hayato Maruyama², Taku Nishimura³, Takuhei Yamasaki³, Junichi Kashiwagi², Tatsuno Takahiro², Shoichiro Hamamoto² (1.Graduate School of Agriculture, Hokkaido University, 2.Research Falculty of Agriculture, Hokkaido University, 3.Graduate School of Agricultural and Life Sciences, The University of Tokyo)

Keywords:Enhanced rock weathering, Carbon dioxide dynamics, basalt application, air-filled porosity

Enhanced rock weathering (ERW) has been suggested as an effective CO₂ sequestration strategy in agricultural systems through the application of crushed silicate rock powders. Based on the two years of field monitoring in the same farmland where crushed basalt powders were applied, the continuous impact of basalt application on soil physical properties and CO₂ dynamics was investigated. Field monitoring was conducted at Hokkaido University on grey lowland soil (43.07 N, 141.34 E) during the 2023 (soybean, Glycine max) and 2024 (feed maize, Zea mays) growing season. Continuous measurements of soil-CO₂, -O₂, and soil moisture, EC, temperature, and water potential were monitored at depths of 10, 25, and 40 cm under four treatment regimes: Basalt-No Crop (BNC), Basalt-Crop (BC), No Basalt-Crop (NBC), and No Basalt-No Crop (NBNC, only in 2024). In addition to the gradient method for estimating CO₂ flux and soil production rates, a chamber method was applied to validate the gradient-based calculations. In 2023, with BC plots, CO₂ concentration increased significantly at 10 cm as compared to NBC. The estimated CO₂ flux from 10cm deep to the atmosphere based on the observed soil CO₂ gradient was higher for the BC plot as compared to the NBC plot. However, in 2024, the CO₂ concentration was similar between two treatments. Although in 2023 basalt addition could enhance water retention and improve acidic soil conditions to enhance CO₂ production, consistent effects of Basalt application were not observed in 2024. Based on the soil chemical analysis such as pH and dissolved organic carbon, the continuous effects of basalt application will be discussed.