Landscape study of microbial divesity in Swiss arable soils
Organic amendments such as compost are widely promoted for enriching soil microbial communities and supporting key soil functions, yet their effects across diverse farming systems and pedoclimatic conditions remain poorly understood. Most evidence originates from controlled experiments that cannot account for the variability inherent in real agronomic settings. Here, using data from 56 commercially managed wheat fields under different fertiliser regimes (compost, solid digestate, or manure) across Switzerland, we show that compost application reshapes soil microbial communities under real farming conditions. Compost increased fungal diversity, shifted fungal community composition, and markedly enhanced fungal network complexity, with effects that exceeded those of the overall management system (organic versus conventional). While compost effects were strongest for fungal communities, 13 bacterial and nine fungal taxa also increased in abundance following frequent compost application. Additionally, we identified a distinct microbial cluster enriched with compost-responsive taxa, including members of Thermoactinomycetaceae-a family commonly found in compost-suggesting the introduction and persistence of compost-derived microbes in agricultural soils. In contrast, solid digestate from biogas plants had weaker and more variable effects on soil microbial communities. Compost application was further associated with higher soil respiration, mediated primarily by changes in soil physicochemical properties and to a lesser extent by shifts in microbial community traits. Together, the results demonstrate that compost application consistently structures soil microbial communities across landscapes. Our landscape-scale on-farm study emphasises compost as an effective practice for strengthening microbially mediated soil processes and promoting sustainable soil management.
BioProject