Paenibacillus–Pseudomonas Consortium Improves Barley Performance with Minimal Impact on Native Rhizobacterial Community

The intensive use of mineral nitrogen fertilizers in cereal production contributes to environmental degradation, highlighting the need for more sustainable crop management strategies. Plant growth-promoting bacteria (PGPB) offer a promising alternative; however, their effects on native rhizosphere communities remain underexplored, particularly in barley. This study evaluates the impact of a bacterial consortium composed of <i>Paenibacillus</i> sp. Z15 and <i>Pseudomonas</i> sp. KR227 on barley growth, yield, and rhizosphere bacteria under field conditions in temperate climate (2025). Plant biometric traits, photosynthetic pigment content, and soil properties were measured, and rhizobacterial communities were analyzed using 16S rRNA gene (V3-V4) sequencing. The PGPB consortium significantly increased early root biomass (120%), shoot height (7.8%), and grain yield (15.5%), while no significant effects were observed on soil chemistry or photosynthetic pigments. Sequencing revealed no major changes in alpha or beta diversity; however, transient shifts in the relative abundance of specific taxa were detected relatively shortly after inoculation and mostly disappeared by harvest. These findings indicate that the <i>Paenibacillus-Pseudomonas</i> consortium can enhance barley performance without disrupting native rhizobacterial communities. Overall, the results support the potential of PGPB as a sustainable agronomic tool and provide new insights into PGPB-microbiome interactions in barley under field conditions.