Effectiveness of enhanced mineral weathering as a carbon sequestration tool and alternative to agricultural lime: An incubation experiment

Applying finely ground silicate minerals to soils could mitigate CO2 emissions by enhancing the rate of carbon sequestration via silicate weathering. Using these minerals instead of agricultural lime to increase soil pH would also eliminate the dissolution of lime as a major source of agricultural CO2 emissions. However, dissolution rates of silicate minerals in the soil environment are uncertain and impacts of their application on the decomposition of soil organic matter have yet to be determined. A 3-month soil incubation was performed to investigate the effects of olivine, a highly weatherable silicate mineral, at two application rates (OLIVlow, OLIVhigh) on soil CO2 flux, available Mg and Al, and pH in comparison to control and lime-amended soils. There was no difference in cumulative net CO2 flux between the olivine-amended soils and the control though total flux from the limed soils was 221% higher than the control. Heterotrophic respiration was also greatest in the lime-amended soils. The weathering rate of OLIVlow (26.7%) was higher than of OLIVhigh (7.1%), but both treatments increased soil pH to a level sufficient to overcome aluminum toxicity. Our results suggest that olivine amendments are an effective tool for carbon sequestration and a suitable replacement for lime.