Edaphic properties override the influence of crops on the composition of the soil bacterial community in a semiarid agroecosystem

Annual cropping systems are dynamic environments where soil bacterial communities are responsive to various management practices such as crop rotations, and to seasonal fluctuations of edaphic properties. However, in semiarid regions the impact of crops on the soil bacterial community appears to be modulated or affected by edaphic properties such as soil moisture availability. Therefore the objective of this study was to determine the relative influence of crops (wheat, lentil, field pea, canola, and a fallow treatment), soil chemistry, and edaphic properties on the diversity and composition of soil bacterial communities in a semiarid agroecosystem. We used a temporal sampling strategy and high throughput sequencing approach to monitor changes in the soil bacterial community in relation to crop host identity and phenology and soil properties. Structuring of the bacterial community across the 20 experimental plots was driven primarily by soil pH which varied strongly (min: 5.25, max: 6.97) across the site. Weak temporal shifts in the bacterial community were observed across the growing season and were related to seasonal variation in soil moisture (min: 8.3%, max: 20.3%), soil temperature (min. daily mean: 3.3 °C, max. daily mean: 21.1 °C), and fluctuation in available phosphate in the soil (min: 0.003 μg cm−2 day−1, max: 0.290 μg cm−2 day−1). These temporal and spatial shifts were not influenced by crop host identity as similar bacterial communities were observed among the crops and fallow treatment. Variance partitioning revealed that soil pH and soil moisture accounted for a high proportion of the variation of the soil bacterial community, while crops had no significant impact in the study. Edaphic factors appeared to override or level the effect of crops on the soil bacterial community. These results highlight the importance of accounting for edaphic properties for managing soil bacterial communities in agroecosystems.