Plant Microbiomes and Soil Health in Sustainable Agriculture: Mechanisms, Bioinoculants, and Future Directions

Soil and plant-associated microbial communities represent one of the most functionally complex and ecologically significant biological networks on Earth. Over the past two decades, rapid advances in sequencing technologies and meta-omics approaches have dramatically expanded our understanding of how plants recruit, shape, and interact with their associated microbiomes across the rhizosphere, phyllosphere, and endosphere. This review synthesises current mechanistic understanding of plant–microbiome interactions, evaluates the status and limitations of bioinoculant technologies, and charts priority directions for future research and applied practice. The literature reviewed in this article was identified through systematic searches of the academic databases Web of Science, Scopus, PubMed, and Google Scholar. Searches were not restricted by geographic region or crop system. The primary date range for recent literatures, with the inclusion of foundational older studies where they established conceptual frameworks of continued relevance. The microbiomes mediate critical agronomic functions including nutrient acquisition, phytohormone production, pathogen suppression, and induced systemic resistance, all of which are foundational to sustainable agricultural systems. Simultaneously, soil health—increasingly operationalised through biological indicators such as microbial biomass, diversity, and enzymatic activity—has emerged as a central concern in global food security discourse. Bioinoculants, including plant growth-promoting rhizobacteria (PGPR) and mycorrhizal fungi, offer promising biotechnological avenues for reducing synthetic input dependence whilst enhancing crop productivity. However, the translation of laboratory findings into field-scale applications remains impeded by ecological contingencies, regulatory barriers, and knowledge gaps in microbiome engineering. The study argues that an integrative systems-level approach—combining microbial ecology, molecular biology, agronomy, and digital technologies—is essential to realise the full agricultural potential of plant microbiomes.