The use of biochar in agricultural soils: Impacts on vineyard productivity and the potential for carbon capture and sequestration

Background Viticulture is increasingly exposed to water deficit, heat and soil degradation, prompting interest in biochar as a soil amendment that may simultaneously improve productivity and sequester carbon. Methods This integrative review used a documented Scopus search (June 2026), targeted searches (September 2026), explicit eligibility criteria and a PRISMA-style flow diagram. All vineyard field trials were tabulated, meta-analyses were reported with effect and sample sizes, and each conclusion was graded by level of evidence. Results Significant yield gains were confined to three Tuscan vineyards amended with the same 500 °C orchard-pruning biochar on acidic to neutral, carbon-poor, non-irrigated soils (+16% to +67% per harvest, persisting ten years after application), and eight site-level comparisons, six in humid-temperate, cool or calcareous-alkaline settings, showed no significant yield response, whereas increases in soil water and topsoil organic carbon were more consistent. The most robust climate outcome is the persistence of the biochar carbon (inert fraction unchanged after 15 years, 65–89% remaining after 100 years), whereas N2O and CH4 reductions are not robust at field scale and remain undetected in vineyards. The previously cited 7.5 Mg CO2-eq ha-1 yr-1, the mean of all soil‑carbon practices in vineyards, rests on very few biochar observations, whereas a single 16.5 t ha-1 (dry) application stores 31–42 Mg CO2-eq ha-1 over 100 years before life-cycle emissions. Without a yield response, the break-even carbon price for biochar costing €200–500 t-1 is €90–243 per t CO2-eq, against a carbon-removal index of €135 (2026), and a single application requires 22–48 years of a vineyard's own prunings. Conclusions Carbon storage in the biochar itself is well supported, agronomic benefits are demonstrated only for a narrow pedoclimatic domain and require independent replication, and greenhouse-gas co-benefits, long-term microbial effects, economic viability and large-scale carbon farming remain plausible but poorly documented or speculative.