Diversity and activity of free-living diazotrophic and total bacterial communities in organic and conventionally managed soil

Agricultural soils are heterogeneous environments in which conditions affecting microbial growth and diversity fluctuate widely in space and time. In this study, the molecular ecology of the total bacterial and free-living nitrogen fixing communities in soils from the Nafferton factorial systems comparison (NFSC) study in North East England were examined. The field experiment is factorial in design with organic versus conventional crop rotation, crop protection and fertility management factors. Soils were sampled on three dates (March, June and September) in 2007. Total RNA was extracted from all soil samples and reverse transcribed. DGGE and qPCR were used to analyse nifH and 16S rRNA genes in order to study free-living diazotrophs and the total bacterial community respectively. Crop rotation was shown to have a significant effect on total bacterial diversity (and that of free-living N fixers) (P=