Enhanced CO2 removal and improved carbon budget by enhanced rock weathering: A field experiment in Hokkaido, Japan

Climate change affects food production, increasing the need for CO ₂ reduction strategies. Enhanced rock weathering (ERW), which involves the spreading of crushed silicate rock powder on agricultural soil to sequester atmospheric CO ₂ via enhanced natural weathering, shows potential to enrich the agricultural soil. In this study, we evaluated the short-term impacts of basalt powder on CO ₂ emissions in rhizosphere and non-rhizosphere soils and estimated the field carbon budget in an experimental soybean field at Hokkaido University, Japan. Basalt powder application at 143 t ha ^− 1 significantly increased the soil pH and reduced the soil volumetric water content. ERW-induced CO ₂ removal rate was 0.81 ± 0.17 Mg C ha ^− 1 , with approximately 86.4% observed in rhizosphere soil, suggesting that factors, such as the exudates produced by crop root growth, enhance basalt weathering and promote CO ₂ removal. Regardless of treatment, the carbon budget was negative, indicating the overall carbon loss in the field. However, basalt powder application reduced the carbon loss from 2.69 ± 0.41 to 1.90 ± 0.73 Mg C ha ^− 1 , but the difference was not significant. These findings suggest that basalt powder application effectively mitigates soil carbon loss and maintains the farmland carbon balance. However, further research is necessary to explore the long-term effects of ERW on soil carbon dynamics and elucidate the underlying mechanisms.