Next-generation Microbial Technologies for Sustainable Agriculture: A Critical Review of Advances in Plant–microbe Interactions, Biofertilisers and Microbiome Engineering
Microbial technologies are increasingly promoted as a route to lower the environmental burden of crop production while sustaining yields, yet the distance between mechanistic promise and reliable field performance remains substantial. This critical narrative review examines the current state of three interlinked domains: the ecology of plant–microbe interactions, the development of biofertilisers and microbial inoculants, and the emerging practice of microbiome engineering. The literature was identified and verified through Crossref Metadata Search and the international Digital Object Identifier resolution system, complemented by citation tracing of recent reviews, with an emphasis on peer-reviewed evidence published between 2011 and 2026. The synthesis shows that the conceptual foundations of the field, including community assembly, host filtering and the holobiont perspective, are comparatively secure, whereas the translation of these principles into dependable agronomic tools is not. Mechanisms of plant growth promotion such as phytohormone modulation, nutrient mobilisation and induced systemic resistance are well characterised under controlled conditions, but their expression in the field is strongly modulated by soil context, host genotype, resident community resistance and formulation quality. The evidence for engineered associative nitrogen fixation in cereals, host-mediated microbiome selection and synthetic community design is mechanistically compelling yet largely confined to proof-of-concept studies. Recurrent weaknesses include short experimental horizons, geographical concentration of trials, inconsistent reporting and a scarcity of independent replication, which together sustain an efficacy–reproducibility gap. The most defensible near-term gains lie in resident-aware inoculant design, standardised multi-site trialling and the integration of microbiome phenotypes into crop breeding, while the ecological and biosafety implications of deliberate microbiome manipulation require structured assessment. Confidence in current conclusions is calibrated accordingly, and priorities are proposed to move the field from descriptive potential towards demonstrated agronomic value.