Soil bacterial diversity related to soil compaction and aggregates sizes in potato cropping systems

Abstract Soil microorganisms play a key role in soil physical structure. Soil microbial community structure and functions are in turn affected by soil aggregation or degradation. The objectives of this study were to determine the impact of (1) soil aggregate-size distribution and (2) soil compaction on bacterial community richness and structure under three intensive potato (Solanum tuberosum) cropping systems. In June and July 2014, soil samples were collected at a depth of 0-20 cm from 16 sites in Quebec, Canada. The samples were analyzed for aggregate-size distribution, particle-size distribution, total carbon, total nitrogen, total sulfur, oxalate-extractable potassium and phosphorus, gravimetric moisture content, pH and degree of compactness (DC). Soil bacterial community diversity was assessed by using the high-throughput sequencing Illumina MiSeq platform to target the V6-V8 region of bacterial 16S rRNA gene. Bacterial alpha diversity and community structure were found to be affected by cropping systems. Faith's phylogenetic diversity index and bacterial richness increased with increasing proportions of the 1–0.5 mm and 2–1 mm aggregate-size fractions and micro-aggregates in soils. Redundancy analysis revealed a strong correlation between soil bacterial community structure and soil aggregate-size distribution. Eight of the 27 dominant bacterial classes had a significant relationship with aggregate size fractions >2 mm, 1- 0.5 mm and