Denitrification is a key process responsible for the majority of soil nitrous oxide emissions but the environmental and management influence on the underlying denitrifier community remains poorly understood. We hypothesised that the abundance and community structure of the total bacterial community and bacterial denitrifiers would be pH sensitive and they would differ in their response to changes in pH and cultivation. We investigated the effect of long-term pH adjusted soils (pH 4.to pH 6.6) under a cultivation gradient (three years of ley grass) on the bacterial and denitrifier functional communities using 16S rDNA, nirK and nirS genes as markers. Denitrifier abundance increased with pH and acidic soil, pH below 4.7, showed a greater loss in nirS abundance per unit drop in pH than soils above this threshold. All community structures responded to changes in soil pH whilst cultivation only influenced the community structure of nirK. These different dynamics in denitrifier communities highlight the of considering both nirK and nirS gene markers for predicting denitrification activity. Identifying thresholds in response to environmental or management changes, as shown here for nirS under acidic pH, is vital to understand functional microbial community dynamics.