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

The rhizosphere is a dynamic interface at which plant carbon allocation, soil chemistry, microbial interactions and environmental conditions jointly influence crop nutrition, disease resistance and stress responses. Although sequencing and synthetic-community experiments have identified numerous plausible microbial mechanisms, improved microbial function does not necessarily translate into reliable field-scale yield benefits. This critical narrative review evaluates research published from 2011 to 10 August 2026, while retaining foundational earlier evidence where needed, to distinguish the ecological assembly of crop-associated microbiomes from the mechanisms and agronomic outcomes attributed to them. Literature identified through accessible scholarly indexes and citation tracing was interpreted according to study design, causal leverage, outcome measurement and environmental transferability. The synthesis examines root exudation and spatial niche formation; host genotype and microbial recruitment; nitrogen, phosphorus and iron acquisition; disease-suppressive communities and immune signalling; drought-associated restructuring; and microbial inoculant performance. Strong experimental evidence shows that plants select subsets of soil microorganisms, metabolites can alter colonisation and cross-kingdom interactions influence host phenotypes. Yet community shifts alone do not establish beneficial function. Nutrient and disease-suppression mechanisms are demonstrable in controlled systems, whereas field responses depend strongly on soil nutrient status, resident biota, cropping history, developmental stage and seasonal stress. In particular, successful inoculant establishment is not equivalent to agronomic efficacy, and beneficial effects on early biomass cannot automatically be interpreted as gains in harvested yield or resource-use efficiency. The principal unresolved challenge is therefore predictive translation rather than proof that microbiomes influence plants. Progress requires spatially and temporally resolved experiments, absolute microbial measurements, mechanism-specific perturbations, sufficiently powered multi-site field trials and pre-defined crop-level outcomes. Microbiome-informed agriculture is most defensible as a context-dependent complement to soil, crop and disease management, not as a universal substitute for them.