Assessing the biogeochemical impacts of terrestrial enhanced rock weathering on soil fertility

Terrestrial enhanced rock weathering (ERW) is a promising carbon dioxide removal technology that consists in applying ground silicate rock on agricultural soils. ERW efficiency is based on the carbon dioxide sequestration associated with the chemical weathering of silicate minerals. On top of carbon sequestration, this chemical weathering can most notably raise the soil pH and release nutrients, thereby potentially improving soil fertility. Despite these possible cobenefits, potential drawbacks such as heavy metal pollution or soil structure damage have also been raised. Yet to our knowledge, these potential effects of ERW on soil fertility have not been simultaneously investigated. This field trial assessed the impact of ERW on biological, physical, and geochemical dimensions of soil fertility. Overall, basalt addition had a predominantly positive to neutral effect on soil fertility. The majority of soil properties showed no significant change either 1 month or 1 year post basalt application. Nevertheless, our study highlighted a significant increase in earthworm biomass, soil respiration and sodium concentration as early as 1 month post application. These changes, suggestive of rapid initial weathering processes, require further investigation before enhanced rock weathering can be considered a viable and secure carbon dioxide removal technology.