Soil Organic Matter Dynamics and Soil Health: A Critical Synthesis of Formation, Persistence, Function and Management

Soil organic matter (SOM) is central to soil functioning, yet its significance cannot be inferred reliably from bulk carbon concentration alone. The processes that generate, transform, redistribute and protect organic compounds operate across interacting biological, mineralogical, hydrological and management gradients. This critical narrative review evaluates how contemporary understanding of particulate organic matter, mineral-associated organic matter and microbial transformation changes interpretations of soil health and agricultural carbon management. Peer-reviewed experimental studies, long-term field investigations, meta-analyses and conceptual papers were selected through topic-specific scholarly searching and citation tracing, with particular attention to contrasting results and measurement limitations. Evidence supports substantial roles for organic matter in aggregation, nutrient cycling, biological habitat and, in particular settings, hydrological regulation. The magnitude and direction of these functions nevertheless depend on soil texture, mineralogy, climate, depth and the composition and spatial distribution of carbon pools. Microbial-derived material contributes importantly to mineral-associated organic matter, but mineral association is neither a guarantee of permanence nor a direct measure of biological usefulness. Meta-analyses indicate that cover crops and organic amendments can increase soil carbon, while benefits differ among fractions, soil layers and management histories. The assumption that no-tillage necessarily sequesters carbon is weakened when whole-profile stocks and equivalent soil mass are considered. Likewise, observed carbon–yield and carbon–water relationships should not be interpreted as invariant causal responses. The review argues for a function-oriented framework that assesses organic carbon stocks alongside accessibility, turnover, aggregation, nutrient supply and context-specific biological indicators. Its priorities include long-term depth-resolved experiments, transparent fractionation, source tracing, whole-system greenhouse-gas accounting and locally calibrated soil-health benchmarks. SOM management is most defensible when it seeks multiple measurable soil functions rather than treating a single carbon indicator as a universal proxy for resilience or climate benefit.