One of the Earth’s largest, most diverse and complex microbiomes is found in the soil (Bardgett and van der Putten 2014; Banerjee and van der Heijden 2023). The soil microbiome may be defined as all microorganisms (archaea, bacteria, fungi, protists, phages and other microbial eukaryotes) contained in the soil (Fierer 2017). A single gram of soil contains as much as 0.5 mg of microbial biomass and over 50 000 species (Banerjee and van der Heijden 2023). This microbial biomass is dominated by fungi and bacteria, and global estimates of the microbial biomass in terrestrial soils indicate that there are 12, 7, 1.6 and 0.5 Gt of carbon (C) contained in fungi, bacteria, protists and archaea, respectively (Bar-On and Milo 2016). Bacteria and fungi typically have 102–104 times greater biomass than the other major components of the soil microbiome (protists, archaea and phages) (Fierer 2017). Humanity relies on the soil microbiome for the secure provision of food and fibre via ecosystem services that include but are not limited to, nutrient cycling, soil organic matter (SOM) development, carbon sequestration and soil structural stability. In addition, the soil microbiome can contribute to unwanted outcomes with negative consequences (e.g. greenhouse gas emissions).