Different farming systems could respond to biological and climate stress in different ways because of underlying differences in biological diversity associated with farming systems that affect plant-plant and plant-microbe interactions. To assess impact on winter wheat production from farming systems, climate conditions, and biological stress from wheat streak mosaic virus (WSMV) and Bromus tectorum, we conducted an experiment at the Fort Ellis research farm (Bozeman MT, USA) recording yield, weed richness and abundance, and soil microbial communities. We analyzed differences in response to farming system (no-till with chemical input (CC), organic utilizing tillage for weed control and crop termination (OT), and organic utilizing sheep grazing (OG)). Within farming system, we manipulated climate that included an ambient climate, a hotter climate using open-top chambers (OTCs), or hotter and drier climate using OTCs and rain-out shelters (ROS) that block 50% of precipitation. Half the plots received WSMV. Soil was sampled monthly from subplots to determine bacterial diversity using Illumina sequencing of the V3-V4 regions of the 16S rRNA gene, as well as nutrient components.
Preliminary analysis of bacterial diversity indicates that day and farming system were the most significant factors. Climate stress increased diversity (OTUs) early in the growing season but reduced it by June in CC and OG. WSMV slightly increased diversity in CC and OT. Overall diversity was highest in June. CC was correlated with Flavobacterium and Arthrobacter, both nitrogen fixers, and negatively correlated with Skermanella, a non-nitrogen fixer. OG was correlated with Skermanella and Nocardioides, previously found in wheat fields and shown to degrade mycotoxins, and negatively correlated with Gemmatimonas. OT was correlated with Gemmatimonas, Arthrobacter, Gaiella, Blastocatella, and Byrobacter. WSMV was negatively correlated with unclassified Actinobacteria, and climate stress was positively correlated with Cellulomonas, a fiber digester that has previously shown to grow best at 40°C and pH 10. Marmoricola was positively associated with wheat yield and wheat biomass, and has previously been isolated from wheat heads. Sphingomonas was correlated with yield, and has been previously associated with wheat rhizospheres. Skermanella was negatively correlated with yield. Wheat protein was positively correlated with Haliangium and negatively with Nocardioides. Weed density and diversity negatively affected wheat production, and only a few weeds had bacterial associations, suggesting that they were not significant drivers of diversity.