Recent research has shown that agricultural management affects microbial biomass and community composition. We investigated the functional implications of such effects in terms of barley biomass production and nutrient acquisition, and whether changes in barley nutrient status affected aphid fecundity. Soils were collected from conventional, ley and organic arable fields and used as inocula in a glasshouse experiment. We determined microbial biomass and community composition using PLFA. We investigated barley growth and nutrient responses to the different soil inoculums, and the impact of excluding arbuscular mycorrhizal fungi (AMF). Aphids were applied to plants within clip cages and numbers of offspring counted. Microbial biomass and community composition were unaffected by agricultural management. The microbial communities altered root and shoot biomass and nutrient allocation, but had no effect on grain yield. Exclusion of AMF significantly increased shoot biomass but reduced grain yield. Aphid fecundity was not significantly affected by the microbial community or shoot nitrogen. We conclude that agricultural intensification does not necessarily have negative consequences for above- and below-ground interactions, and microbial communities from conventionally managed soils may offer equal benefit to crop productivity and nutrition as those from organically managed soils.