Organic Matter Dynamics in Soil

Abstract

Soil Organic Matter (SOM) is a viscoelastic, multi-phase substance found in soils. It is heterogeneous in structure and biochemical composition and influences nearly all soil processes such as soil aggregation, water infiltration, soil reaction (pH), ion-exchange reactions, microbiological properties, nutrient cycling, and pollutant behavior. SOM is thus a key determinant of soil health and quality. Increased SOM levels enhance plant productivity and soil health, whereas its depletion leads to soil degradation and can eventually result in desertification. The decline of SOM is largely driven by agricultural management practices that accelerate the decomposition of stable SOM pools. Sustainable management practices can help maintain or increase SOM, though changes occur gradually over years to decades, depending on soil properties, climate, and crop residue management. Assessing SOM dynamics at larger spatial scales often relies on measuring Total Organic Carbon (TOC) pools over time, but this approach has limitations, as it does not fully capture decomposition pathways, protection mechanisms, or turnover rates.