Carbon sequestration and stabilization in soils: Implications for soil productivity and climate change

This review describes various currently proposed mechanisms of carbon (C) sequestration and stabilization in soils and how an understanding of the mechanisms provides the key to the control and regulation of soil organic C (SOC) levels. This has important implications on soil productivity and the potential of using soils to enhance soil C storage and reduce greenhouse gases (GHGs) in the atmosphere for mitigating predicted climate changes. Globally, most agricultural and degraded soils can provide significant potential sinks for atmospheric CO2. However, soil C accumulation does not continue to increase with time with increasing C inputs but reaches an upper limit or "C saturation level," which governs the ultimate limit of soil C sink. The control of this limit relies on understanding soil C stabilization mechanisms. Physical mechanisms such as protection of SOC by soil minerals are better known while chemical and biological mechanisms are less well known, requiring more experimental data for verification and validation. No study has yet compared the relative significance of each of the proposed major mechanisms in a given soil type and climate. Continued research on this and related aspects are needed if soils are to be relied upon for food and fibre production and for the mitigation of climate change.