Season and management related changes in the diversity of nitrifying and denitrifying bacteria in an Ontario agricultural soil

This research assessed the effects of seasonal variation and tillage practice on the diversity of nitrous oxide producing bacteria in agricultural soil and investigated the dynamics of denitrifiers in a thawing soil in the laboratory. Diversity of the nitrifier and denitrifier communities was assessed by PCR-denaturing gradient gel electrophoresis (DGGE) using primer pairs targeting functional genes. Analysis revealed that seasonal variation had the largest influence on diversity; while tillage practices also influenced the diversity of the microbial communities. Diversity of the communities was the lowest in February, in frozen soils, and rapidly increased in March, after a spring thaw event. The laboratory study indicated that active denitrifiers were related to 'N'2'O' emission during this time, with increased diversity and richness associated with increased ' N'2'O'. Insight into the effects of tillage and seasonal variation on these microbial communities has the potential of improving our understanding of the mechanisms of 'N'2 'O' emissions.