Enhanced Rock Weatherings Effects on Soil and Plant Chemistry in Acidic Biodiverse Grassland

Enhanced rock weathering (ERW) is the process of spreading basalt rock on agricultural soils to absorb carbon dioxide (CO₂). If rolled out globally models predict it could sequester gigatonnes of atmospheric CO₂ by the end of the century (Beerling et al., 2020). Extensive research is being carried out on identifying potential co-benefits of ERW and validating carbon dioxide sequestration within tilled arable soils; the annual nature of crops grown in these soils and their associated fertiliser use causes plants to have limited total root surface areas and disturbed mycorrhizal networks. ERW’s potential in grasslands, where perennial plants dominate with stable root biomass and mycorrhizal partners, is yet to be tested thoroughly. It does offer potential, as previous studies have shown that mycorrhizal fungal association to plant roots enhances mineral weathering (Quirk et al., 2012). To characterise whether grasslands carry any potential as an ERW system 50 tonnes per hectare of basalt was applied in March 2022 to 5 plots, with 5 adjacent plots being left un-treated within a traditional mildly acidic hay meadow in the Peak District. Over the course of the growing season soil pH, cations, phosphorus, and plant available silicon was assessed at regular intervals for treated and untreated samples. Furthermore, plant yield, nutrition data, and biodiversity were also analysed. Results indicate that rock weathering did occur, with significant increases in soil magnesium, silicon, and pH noted over the course of the experiment. There were no significant changes to plant yield, biodiversity, or nutrition in most cases; however, in basalt treated samples there were significant increases in the plant concentrations of silicon, magnesium, strontium, and sodium. Results indicate that ERW could benefit acidic grasslands through its pH and soil nutrient effects, while also potentially resulting in the absorption of CO₂.