Consistent bacterial communities in agricultural soils despite contrasting drainage practices and land management histories. Agricultural soil bacterial communities with contrasting drainage

Soil microorganisms are responsible for nutrient cycling and are an important consideration for effective agricultural soil management, which is essential for achieving optimum crop production and maintaining soil quality. The overall goal of the present research was to better understand microbial communities in agricultural soils as they relate to soil management practices. For this, we evaluated the impact of two contrasting drainage practices on bacterial community composition. Controlled and uncontrolled tile drainage practices maintain water in the field or fully drain it, respectively. Because soil water content influences nutrient concentration, moisture, and oxygen availability, the effect of these two disparate practices on bacterial community composition was compared in paired fields that had diverse land management histories. Libraries of the 16S rRNA gene were generated from DNA obtained from 168 soil samples collected from eight fields during the 2012 growing season. Paired-end high-throughput sequencing was followed by read assembly and multivariate statistical analyses. Results showed that although soil depth, plant cultivar, and fertilizer application impacted bacterial community composition strongly, soil drainage practice exerted only negligible effects. In addition, the only differences in alpha diversity were associated with samples collected from 60-90 cm, which were significantly less diverse than surface soil samples. Although significant indicator species from the phyla Chloroflexi, Proteobacteria, and Actinobacteria were associated with depth-specific samples, no consistent and strong indicators were associated with plant cultivar, applied fertilizer type, nor drainage practice. These results reinforce the overall resilience of agricultural bacterial communities to field drainage practices, which indicates that other outcome indicators, such as plant biomass yield, can be considered when implementing controlled tile drainage within agricultural fields.