Basaltic rock powder addition increases soil macrofauna but shows limited impact on microbial communities: insights from a temperate field trial

Summary

Enhanced rock weathering (ERW) is gaining attention as a scalable carbon dioxide removal strategy involving the application of finely ground silicate rock to agricultural soils. While its potential to sequester between 0.2 and 4 Gt CO2 yr−1 could contribute significantly to global climate goals, concerns remain about its long-term impacts on soil health and biodiversity. In this study, we evaluated the effects of a single 20 t ha−1 basaltic rock powder application on four major soil biota groups—earthworms, arthropods, bacteria, and fungi— within a vineyard field trial in Western Switzerland. Soils were sampled one month and one year after application to assess short- and medium-term impacts. We found that ERW rapidly increased earthworm abundance (+71%) and soil arthropod diversity (Shannon index: +36%) one month post application but had no detectable effect on microbial communities. After one year, earthworm abundance no longer differed from the control, whereas arthropod diversity remained significantly higher in rock powder-treated plots (+27%). Broader field trials across diverse soils and climates using various rock feedstocks and repeated applications are now needed to ensure ERW's safety.