Influence of enhanced silicate weathering on microbial processes and soil carbon formation in agricultural soil

Enhanced silicate weathering (ESW) is an innovative technique to leverage natural processes which usually operate over millions of years to potentially replenish nutrients and carbon (C) in soil. ESW involves applying pulverized silicates to increase reactive mineral surfaces which in turn may speed-up the weathering and scale to aid in global CO₂ removal. However, current studies supporting ESW has been relying on theoretical estimates and short-term laboratory experiments whose results are difficult to extrapolate to the field. Also, many studies have focused on inorganic C chemistry while soil is a rich medium that mediates a multitude of chemical and biological processes, many of which are not well studied but may play an important role in controlling ESW. To address this gap, the Working Lands Innovation Center (WLIC) Project was launched in 2019 for a field scale test, and three commercial amendments (compost, biochar, and silicate powder—meta-basalt) have been applied yearly with a full factorial design in a 2.07 ha corn field at the Campbell Tract research facility located on the UC Davis campus. My project within WLIC evaluates the impact of ESW on soil surface C pools related to microbial processes and its potential synergies with traditional organic amendments. We hypothesized that co-applying organic amendments plus pulverized silicate minerals will: 1) increase microbial biomass with distinct microbial community composition; and 2) increase the formation of stable carbon pools (e.g., mineral associated organic matter) relative to only silicate applied soil. To test this, we sampled soils from all possible amendment combinations at pre-, and post-harvesting seasons in 2021 and 2022. We completed a suite of analyses to monitor temporal changes of soil chemistry, multiple C pool sizes, and microbial parameters. Here, we will examine the causal mechanisms that explain how adding extra C with silicates may change microbial environments and carbon pool dynamics over a two-year period. Our findings will provide critical information whether natural soil processes, such as rock weathering and soil organic C stabilization, can be engineered (and accelerated) for management purposes at agricultural field scale.