Carbon is an important component of the soil and is essential for the maintenance of soil quality. As a constituent part of humus, C serves as a binding agent that holds soil particles into aggregates, and thereby enhances the soil physical properties, particularly porosity, aeration, infiltration, and drainage. Further, polysaccharides secreted by soil microflora can have the same effect, but not to the extent as C. Carbon also serves as a major sink/source of essential plant nutrients. Chemically, it is very important for enhancing soil fertility through improvement in CEC and nutrient retention, and as a source of energy for microorganisms.
Soil C dynamics are influenced by environmental factors such as temperature and rainfall along with anthropogenic factors that include the need for clearing forests and grasslands for farming, farming systems in place, and harvesting forests for timber and wood fuel. In Zambia, the chitemene and fundikila systems of land clearing and preparation, and the felling of forest trees for charcoal and wood fuel, result in a serious loss of soil organic and inorganic C.
Soil C sequestration practices have been recommended to ameliorate these conditions. They include the use of cover crops, green manure, crop rotation, integrated nutrient management systems, reforestation, and conservation tillage to reduce soil disturbances and hence soil erodibility.
Soil organic C sequestration is a highly recommended approach to sequester organic C. Increasing SOM content under current farming systems in Zambia maybe an easier approach to sequester SOC. In the northern part of the country, the chitemene and fundikila systems could be made more productive by increasing biomass accumulation in the miombo woodlands and reducing the burning of vegetation. The introduction of suitable multipurpose trees, herbaceous woody legumes that contain high lignin, polyphenols, and condensed tannins like Calliandra calothyrsus and Gliricidia sepium, would be one way to sequester C, as these materials are C sinks and release C slowly over long periods of time (Malama, 1998). Encouraging water harvesting may help to sequester soil C in the drier areas of Region 1, where the soils are prone to erosion and water is a limiting factor to crop production. In all three agroecological regions, enhancing biomass production and accumulation, and reducing deforestation when clearing land for agricultural production, and lumber and wood fuel harvesting will enhance SOC sequestration for the betterment of soil quality, agricultural sustainability, food security, and a reduction in global warming.
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