Plant–Microbiome Interactions in Agriculture: From Rhizosphere Biology to Crop Health and Productivity

The rhizosphere is a dynamic interface at which plant roots, soil chemistry and microorganisms jointly influence nutrient acquisition, development and responses to environmental stress. Increasingly sophisticated sequencing, metabolomic and experimental approaches have revealed plausible routes through which microorganisms alter plant performance, yet demonstrations of microbial function under controlled conditions do not reliably predict consistent crop benefits in farmers’ fields. This critical narrative review evaluates evidence on rhizosphere assembly, nitrogen and phosphorus nutrition, iron mobilisation, microbial regulation of growth and disease, and resilience to water and other abiotic stresses. It integrates crop field investigations with mechanistic experiments, synthetic-community studies and quantitative evidence syntheses, giving particular attention to experimental controls, outcome definitions, causal inference and environmental heterogeneity. Microbial contributions to nutrient exchange and host defence are well established in particular associations, whereas broader claims about generic growth-promoting taxa and commercially transferable inoculants remain conditional. Drought-related shifts in microbial composition are repeatedly observed, but only selected studies establish that recruited organisms or their metabolites causally improve plant performance. Field trials and meta-analyses suggest potential agronomic benefits while revealing pronounced variability between soil types, host genotypes, management regimes and climatic conditions. This disparity is amplified by compositional sequencing data, imperfect colonisation measurements, short trial durations and the routine extrapolation of pot experiments to complex soils. A more reliable framework for crop microbiome management must connect mechanism to context-specific prediction and explicitly measure nutrient budgets, yield stability, ecological persistence and economic value. Future progress depends on multi-season field experimentation, factorial comparisons with conventional inputs, strain-resolved tracking, integrated absolute-abundance and functional measurements, and transparent reporting of negative outcomes. Rhizosphere management is therefore best understood as a potentially valuable complement to, rather than a universally proven substitute for, plant breeding, soil stewardship and judicious nutrient management.