Understanding the roles of microbial communities in governing nutrient transformations is required for developing accurate predictions of manure nutrient availability across soils and ecoregions.  Despite this importance, little research has been conducted to link process level nutrient transformations, such as nitrification, to changes in microbial community dynamics. We evaluated the effects of manuring and beta-ammonia oxidizer community dynamics on nitrification potentials across eight soils from a wide range of ecoregions. Each soil was used in a 30-d incubation containing a dairy slurry (300 kg N ha^-1) amended soil and a soil control. Sub samples were removed at 5 time intervals for analyses of nitrification potentials and community structure of beta-ammonia oxidizers via denaturing gradient gel electrophoresis (DGGE).  Soil series had a significant influence on nitrification potential and microbial community structure.  DGGE migration patterns relative to cluster controls indicated that some cluster groups of beta-ammonia oxidizers varied among soil series.  Manure addition affected the rate of nitrification but not the microbial community structure.  Nitrification rates appeared to be controlled by the community composition at the start of the incubation.  Dairy slurry may have increased nitrification by providing substrate to static cells of beta-ammonia oxidizers.  Further research via real-time PCR is planned to measure community evenness in order to gain additional insight into these relationships.