Soil microbiomes play an integral role in agricultural production systems. Understanding of the complex microbial community structure and responses to conventional compared to organic cropping systems is crucial for sustainable production and ecosystems health. This study investigated soil microbial community structure responses based on a four year long field experiment. Bacterial communities characterizing conventional and organic cropping systems were evaluated using Illumina MiSeq high-throughput sequencing targeting the V4-V5 variable region of the 16S rRNA gene. Soil bacterial community structure showed a cropping system dependant distribution, with nitrogen cycling taxa (Bacillus, Niastella, Kribbella, and Beijerinckia) dominant in conventional cropping systems, while carbon cycling taxa (Dokdonella, Caulobacter, Mathylibium, Pedobacter, Cellulomonas and Chthoniobacter and Sorangium) were abundant in organic cropping systems. Functional prediction of the bacterial biomes showed conventional cropping systems to harbour a community adapted to carbon-limited environments, with organic cropping systems dominated by those involved in the degradation of complex organic compounds. These findings suggest the existence of niche specific communities and functional specialization between cropping systems with potential use in soil management through selective promotion of organisms beneficial to soil health.