Variation of Bacterial Communities within a Consociation Soil Map Unit.

Soil microorganisms drive biogeochemical cycling. These soil microbial communities differ based on pH, soil moisture, texture, organic carbon, and available nutrients. Furthermore, soil microbial diversity and abundance decrease with depth in a soil profile. The objective was to determine whether soil microbial communities differ across a soil map unit. We hypothesized that soil microbial communities will be similar within a soil map unit. We sampled at 10 randomly located sites in a field mapped as Windthorst consociation that was used as a dairy effluent waste application field. At each site, we dug a pit to parent material and sampled by horizon, and 4 satellite surface samples were also collected. We characterized soils by pH, texture, calcium carbonate equivalence, total nitrogen, and total carbon. Microbial communities were analyzed using massively parallel DNA sequencing, and separated into Operation Taxonomic Units (OTUs) based on 97% sequence similarity. We analyzed results through Qiime using PERMANOVA, Mann-Whitney U, and Spearman’s rank correlations. Results showed relatively homogenous soil properties across the field. There were no differences in microbial communities within each site. When the ten sites were compared against one another, differences in 4 phyla were observed. Four OTUs also varied by site. Microbial communities were also dependent on phosphorus. 3 phyla and 21 OTUs varied with phosphorus concentrations. We suggest soil microbial communities have very little variation over short distances (<5 m), but have greater changes over greater distances. Bacterial communities likely change in response to changes in soil properties such as nutrients.