European Journal of Sustainable Agroecosystems

Background: Conservation agriculture (CA), built on the principles of minimum mechanical soil disturbance, permanent soil organic cover, and diversified crop rotations, is widely promoted as a nature-based strategy to enhance soil organic carbon (SOC) stocks and mitigate agricultural greenhouse gas emissions. However, evidence on the magnitude, depth distribution, and permanence of SOC gains under long-term CA remains fragmented and, in places, contradictory.
Objective This review synthesizes peer-reviewed and institutional literature published between 2015 and 2025 to critically evaluate carbon sequestration dynamics under long-term CA, identify sources of disagreement among studies, and map research gaps.
Method A structured search of Scopus, Web of Science, PubMed, Google Scholar, and reports from the Food and Agriculture Organization (FAO) and the Intergovernmental Panel on Climate Change (IPCC) yielded 1,842 initial records, of which 84 studies met the inclusion criteria following a PRISMA-style screening process.
Result Long-term no-till and residue retention consistently raise SOC concentration in the upper 0-15 cm layer, with reported gains ranging from approximately 4% to over 20% relative to conventionally tilled soils, but effects diminish or disappear when sampling extends beyond 30 cm. Cover cropping increases SOC by roughly 7-15% at shallow depths, with global sequestration potential estimated near 0.12-0.4 Gt C per year. Combining no-till with cover crops, diversified rotations, and integrated crop-livestock systems produces the most consistent gains across agro-ecological zones, while SOC accrual typically follows a saturating curve rather than a linear trajectory. The soil carbon saturation concept, though contested, helps explain why gains plateau after 10-20 years in many systems.
Persistent gaps include shallow and inconsistent sampling depths, short experimental durations, divergent SOC accounting methods (fixed-depth versus equivalent-soil-mass), limited data from smallholder tropical systems, and weak integration of non-COâ‚‚ greenhouse gas trade-offs.
Conclusion CA can deliver meaningful, though context-dependent and time-limited, soil carbon gains. Realizing its climate mitigation potential requires standardized deep-profile monitoring, longer networked trials, and digitally enabled measurement, reporting, and verification (MRV) systems tailored to diverse farming contexts.