Mineralization (soil science)

In soil science, mineralization is the decomposition (i.e., oxidation) of the chemical compounds in organic matter, by which the nutrients in those compounds are released in soluble inorganic forms that may be available to plants.

Mineralization increases the bioavailability of the nutrients that were in the decomposing organic compounds, most notably (because of their quantities) nitrogen, phosphorus, and sulfur.

As carbon dioxide is released during the generation of energy in decomposition, a process called "catabolism", the C:N ratio of the organic matter decreases.

When the C:N ratio is less than circa 25:1, further decomposition causes mineralization by the simultaneous release of inorganic nitrogen as ammonium.

When the decomposition of organic matter is complete, the mineralized nitrogen therefrom adds to that already present in the soil and therefore increases the total mineral nitrogen in the soil.

A conceptual view of C cycling and N cycling during organic matter decomposition. 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. N mineralization leads to a loss of ammonium to the environment (5), but this process is only relevant if the organic matter has a low C:N ratio. Ammonium from the environment can be immobilized if the dead organic matter has a high C:N ratio and thus provides insufficient N (6). The high microbial N demand leads to a retention of N within the organic matter and thus to a decrease of the C:N ratio over the course of decomposition. [ 3 ]