Soils are an important COS sink. However they can also act as sources of COS to the atmosphere. Here we demonstrate that variability in the soil COS sink and source strength is strongly linked to available soil inorganic nitrogen (N) content across a diverse range of biomes in Europe. We revealed in controlled laboratory experiments that N fertilisation simultaneously decreases the COS sink strength of soils while increasing the COS production rate. Furthermore, we found strong links between variations in the two gross COS fluxes, microbial biomass and nitrate and ammonium contents, providing new insights into the mechanisms involved. Our findings provide evidence for how soil-atmosphere exchange of COS is likely to vary spatially and temporally, a necessary step for constraining the role of soils and land use in the COS mass budget.