[A-GE28] Subsurface Mass Transport and Environmental Assessment

[AGE28-04] Enhanced Rock Weathering Impact on Soil CO₂ Dynamics: A Soybean Field Monitoring Study in Hokkaido

*Yan Zhu¹, Jun'ichi Kashiwagi⁴, Hiroshi Uchibayashi¹, Takuro Shinano², Hayato Maruyama², Takuhei Yamasaki³, Taku Nishimura³, Shoichiro Hamamoto² (1.Graduate School of Agriculture, Hokkaido University, 2.Reserach Faculty of Agriculture, Hokkaido University, 3.Graduate School of Agricultural and Life Sciences, The University of Tokyo, 4.Graduate School of Global Food Resources, Hokkaido University)

Keywords:enhanced rock weatherg, carbon dioxide, field monitoring, crushed basalt, soil physical properties

Enhanced rock weathering (ERW) is a technique applying crushed rock powders in agricultural lands to enhance the weathering process, storing CO₂ for negative emission. Researchers investigated several benefits of ERW, such as acidity amelioration, nutrients supply, and CO₂ reduction. However, understandings of how rock powders affect the soil physicochemical properties and CO₂ dynamics at field-scale are limited.
In this study, monitoring was conducted in an experimental field (grey lowland soil) at Hokkaido University (43.07 N, 141.34 E), where soybean (Glycine max) was cultivated in 2023. Continuous data of soil CO₂, O₂, moisture, EC, temperature, and water potential has been collected at depths of 10cm, 25cm, and 40cm, respectively, in four treatments [BNC (Basalt-No crop), BC (Basalt-Crop), LC (Lime-Crop), and NBC (NoBasalt-Crop)]. We also calculated the CO₂ flux and CO₂ production rate in each soil profile.
Soil CO₂ concentration in all treatments increased after rainfall events. Basalt and lime applications in soybean plots significantly increased CO₂ concentration at 10 cm depth. The estimated CO₂ flux from 10 cm depth to the atmosphere based on the observed soil CO₂ gradient was higher for the BC plot (accumulative CO₂ flux until December 1^st: 41.6 mol C m^-2) as compared to the NBC plot (33.6 mol C m^-2). The higher CO₂ emission in ERW plots may indicate enhanced soil respiration due to the dissolution of rock powders (i.e., increase of pH).