Abstract
The use of livestock manure as agricultural soil amendments is a signifcant source of ammonia emissions and nitrate leaching. Anaerobic digestion of manure can yield to solid and liquid by-products usable as fertilizers that can limit these negative impacts. They could be further supplemented with plant growth-promoting microorganisms (PGPM) to improve plant growth and yield. This study investigated the impact of PGPMs and anaerobic digestates on strawberry quality and rhizospheric microbial community. Strawberry plants were grown in soils treated with PGPMs (pure culture of Azospirillum brasilense or a commercial product with efective microorganisms) along with either liquid or solid digestate. Efects of digestates and PGPMs were evaluated by measuring plant yield and nutraceutical values, while the rhizospheric microbial community was assessed through an eDNA metabarcoding approach. Results suggest using PGPMs combined with digestates enhances plant yield, with increases of up to 40-60% in fruit yield and 9-18% in nutraceutical value, compared to the controls. The rhizospheric microbial community was infuenced only by digestates. Nevertheless, these alterations have not led to signifcant changes in the community, thus ensuring its long-term stability. Moreover, PGPMs were not detected into the rhizospheric community. Our data pointed out that both PGPMs and digestates can represent a sustainable approach to increase strawberry plant yield. However, PGPMs require repeated inoculations in long-term projects to achieve and maintain desired outcomes. These fndings emphasize the complexity of rhizospheric microbial interactions and underscore the importance of continued research to optimize agricultural practices while maintaining ecosystem stability.