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Carbon, as it relates to the organic matter of soils, is a major component of soil and catchment health. Several factors affect the variation that exists in soil organic matter and soil carbon; the most significant has, in contemporary times, been the influence of humans and agricultural systems.
The pool of organic carbon exists in dynamic equilibrium between gains and losses; soil may therefore serve as either a sink or source of carbon through carbon sequestration or greenhouse gas emissions, respectively, depending on exogenous factors.
Particulate organic matter (POM): is the organic matter that retains evidence of its original cellular structure, [18] and is discussed further in the next section. Humus: is usually the largest proportion of organic matter in soil, contributing 45 to 75%. Typically it adheres to soil minerals, and plays an important role structuring soil.
Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come from the feces and remains of organisms such as plants and animals . [ 1 ]
Dissolved organic matter (DOM) is one of the most active and mobile carbon pools and has an important role in global carbon cycling. [41] In addition, dissolved organic carbon (DOC) affects the soil negative electrical charges denitrification process, acid-base reactions in the soil solution, retention and translocation of nutrients ( cations ...
The soil microbial population releases exoenzymes (1), which depolymerize the dead organic matter (2). The microbial decomposers assimilate the monomers (3) and either mineralize these into inorganic compounds like carbon dioxide or ammonium (4) or use the monomers for their biosynthetic needs.
Organic carbon held in soil is eventually returned to the atmosphere through the process of respiration carried out by heterotrophic organisms, but a substantial part is retained in the soil in the form of soil organic matter; tillage usually increases the rate of soil respiration, leading to the depletion of soil organic matter. [24]
Soil aggregation can physically protect organic carbon from decay by soil microbes. [19] More aggregate formation can result in more soil carbon storage. There is much evidence that arbuscular mycorrhizal fungi increase soil aggregate formation, and that aggregate formation may be mediated by the arbuscular mycorrhizal protein glomalin . [ 20 ]