Dryland cropping system, weed communities, and disease status modulate the effect of climate conditions on wheat soil bacterial communities.

Little knowledge exists on whether soil bacteria are impacted by cropping systems and disease status in current and predicted climate scenarios. We assessed the impact of soil moisture and temperature, weed communities, and disease status on soil bacterial communities across three cropping systems: conventional no-till (CNT) utilizing synthetic pesticides and herbicides, 2) USDA-certified tilled organic (OT), and 3) USDA-certified organic with sheep grazing (OG). Sampling date within the growing season, and associated soil temperature and moisture, exerted the greatest effect on bacterial communities, followed by cropping system, Wheat streak mosaic virus (WSMV) infection status, and weed community. Soil temperature was negatively associated with bacterial richness and evenness, while soil moisture was positively associated with bacterial richness and evenness. Both soil temperature and moisture altered soil bacterial community similarity. Inoculation with WSMV altered community similarity, and there was a date x virus interaction on bacterial richness in CNT and OT systems, as well as an interaction between WSMV x climate. In May and July, cropping system altered the effect of climate change on the bacterial community composition in hotter, and hotter and drier conditions not treated with WSMV, as compared to ambient conditions. In areas treated with WSMV, there were interactions between cropping system, sampling date, and climate conditions, indicating the effect of multiple stressors on bacterial communities in soil. Overall, this study indicates that predicted climate modifications as well as biological stressors play a fundamental role in the impact of cropping systems on soil bacterial communities.