Abstract
Biological nitrogen fixation is one of the most important nutrient processes in the ecosystem. Many studies have estimated the variations in soil diazotrophic communities across the globe. To understand the dynamics of nitrogen fixing bacterial communities and their response to the environmental changes, it is important to study the temporal variability of these communities. Using DNA fingerprinting method, denaturing gradient gel electrophoresis and real time polymerase chain reaction of the nifH gene, we have found that the agricultural land harbored unique nitrogen fixing communities that revealed different temporal patterns and abundance. Variation in soil moisture, organic carbon content, ammonium and nitrate concentrations may be the main factors which influenced the diazotrophic community composition and nifH gene abundance. Azospirillum species were more dominant in the agricultural soil. Unique environmental factors and agricultural practices were responsible for the temporal shifts in bacterial community structures and nifH transcripts level. Our study expands understanding of the influence of environmental factors on diazotrophic population that contributes to the nitrogen pool.