Modelling the impacts of enhanced rock weathering on soil-plant-carbon cycle: develop and benchmark on mesocosm and field experiments

Enhanced rock weathering (ERW) is a method of carbon dioxide removal (CDR) that relies on the weathering of mineral feedstock in the soil upper layers. Current ERW models, estimating CDR potential from the local site, primarily examine mineral dissolution and ion exchange processes via abiotic pathways within soil columns at mesocosm/plot scale. These models often simplify or overlook the interactions between soil, plants, and carbon dynamics under rock applications. Here, we present a novel integrated modelling approach, coupling an ERW model, SMEW (Bertagni et al., 2024), with the mechanistic ecohydrological model T&C-BG (Fatichi et al., 2019). Our coupled model T&C-SMEW can explicitly represent the hydrological, vegetation dynamics and soil biogeochemical cycling of carbon, nitrogen, phosphorus, potassium and micro-nutrients (Ca²⁺, Mg²⁺, Si) with the aid of T&C-BG, while incorporating mineral dissolution dynamics of SMEW. Additionally, T&C-SMEW accounts for key mechanisms such as a) biological weathering related to the release of H⁺ following realistic plant cation uptakes under varying environmental conditions, and b) strong acid weathering due to N fertiliser applications on crop field. Validated against both mesocosm and field experiments, T&C-SMEW can capture soil mineral exchanges and ecosystem carbon dynamics, demonstrating its reliability for representing ERW application in practical scenarios. By utilising T&C-SMEW, the direct CDR potential (e.g., mineral weathering) of ERW, its co-benefits (e.g., enhanced plant productivity), and associated environmental risks (e.g., phosphorus leaching) can be comprehensively assessed.