Soil restoration via enhanced weathering: insights from a mesocosm experiment

Soil degradation severely limits agricultural productivity, particularly in regions where farming is the primary source of livelihood. Enhanced weathering offers a promising and underexplored approach to restoring these degraded soils while improving their capacity to support plant growth. To evaluate this potential, we conducted a one-year mesocosm experiment in 2025 where we assessed the capacity of a newly engineered soil to support plant growth under controlled conditions. This newly engineered soil consisted of basalt combined with biochar and compost and was applied as a top layer onto a sandy soil mimicking degraded, nutrient-depleted soil. Alfalfa (Medicago sativa) successfully grew on this newly formed soil in contrast with the mesocosms where no new topsoil was added. Furthermore, the experiment investigated how key parameters, like silicate grain size (fine = 0.01-0.09mm, coarse = 1/3mm), mixing regime (mixed vs. layered) and application rate influenced plant performance. Plant performance was quantified through biomass harvests and analysis of macro- and micronutrient uptake, alongside heavy metal concentrations in plant tissue to ensure crop safety.