The conceptual model presented in Figure 17.1 illustrates that carbon sequestration potential is related to soil texture and the intensity of tillage. The greatest potential for carbon sequestration is with fine-textured soils that have been carbon degraded due to intensive tillage. Many such soils exist in developed countries, where large tillage equipment is the norm. In tropical environments of the developing world, soils that are in a paddy rice-upland crop rotation are the most carbon degraded due to puddling of soils to reduce water infiltration, which destroys all but the most stable aggregates. Decomposition of released OC is then rapid in the following aerobic phase of the crop rotation. The lowest potential for carbon sequestration is with light textured soils, even though they may have very low OC levels.
Erosion of topsoil where low OC subsoils become surface soils also creates a situation where carbon sequestration potential is high. Since carbon in eroded soils may well be conserved, the combination of erosion and building up of OC in former subsoils may well lead to greater overall carbon storage than originally existed before erosion occurred (Dux-bury, 1995). This is not to say that erosion should be promoted, of course, since it has a range of negative side effects.
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