UC Davis

Silicate weathering is a primary control on Earth’s climate as this process transforms atmospheric CO2 dissolved in water into solid and aqueous mineral forms. Enhanced silicate weathering (ESW) increases the surface area of this natural reaction by using pulverized silicate rock which increases mineral weathering rates, thus increasing CO2 consumption associated with mineral dissolution, and increases the reactivity of silicates by applying ground rock to soils or oceans, where H+ enhances dissolution rates. My thesis explores the efficacy of ESW to store CO2 as inorganic C in soil to decrease radiative forcing caused by anthropogenic greenhouse gas (GHG) emissions. I utilized two silicate minerals, wollastonite and basalt, in a 2-year field study with corn and tomato to ascertain the efficacy of this method to achieve inorganic C storage significant to climate mitigation. I assessed crop yield, soil nutrient content, crop nutrient content, as well as inorganic C formation to draw conclusions about the advantages of enhanced mineral weathering in agriculture. We observed yield and pH increases in both crop types, however only corn showed significant storage of atmospheric carbon (C) as HCO3-. Another objective of my research is to determine if ESW will become more effective in future conditions as atmospheric CO2 and temperature levels continue to rise. We measured yield, alkalinity, pH, and soil and crop nutrient content with soybean amended with basalt alone and basalt in combination with compost in a controlled growth chamber under two climate regimes: ambient CO2 and temperature and elevated CO2 and temperature. In ambient conditions, we saw no effect of silicate addition on soybean yield and alkalinity, while in elevated conditions, we observed significant treatment effects in yield, alkalinity, and pH. Results in these field and pot studies support the use of ESW as a CO2 drawdown pathway and fertilizer supplement in certain crops. Future studies should continue to assess ESW in fertile, well-buffered soils to determine their efficacy in agricultural environments.