Agricultural systems are being asked to raise output while cutting fertiliser losses, restoring degraded soils and contributing to climate mitigation. Two material-based technologies have attracted sustained attention in response: biochar, the carbon-rich solid produced by pyrolysing biomass under limited oxygen, and nano-enabled inputs such as nanofertilisers, nanopesticides and nanoscale sensing platforms. Increasingly the two converge in nano-biochar and biochar-supported nanocomposites, which pair biochar’s porous, carbon-stable matrix with the reactivity and delivery precision of nanomaterials. This narrative review synthesises literature published between 2023 and 2026, together with a small number of earlier foundational papers, retrieved from Scopus, Web of Science, PubMed and Google Scholar. It describes the dominant production routes and modes of action, then assesses the evidence base. Global meta-analyses report average crop yield gains in the range of roughly 10–42 per cent for biochar, with the strongest responses in acidic, sandy, low-fertility and salt-affected soils and negligible responses in fertile temperate systems. Recent independent assessments place the sustainable climate mitigation potential of biochar systems at several petagrams of carbon dioxide equivalent per year. Nano-enabled inputs show comparable promise for nutrient use efficiency, but the evidence remains dominated by pot and greenhouse studies. Persistent barriers include feedstock competition, cost, weak regulatory definitions, ecotoxicological uncertainty and a shortage of multi-season field validation. The paper argues for standardised reporting, targeted deployment in constrained soils, and integrated physiological and soil-science experimental designs.