Mineralization is the process of converting elements from an organic form to an inorganic form by microbial decomposition. After the addition of organic materials to soil, the rate of release of carbon dioxide reaches a peak in a few days and then tapers off with time. The peak is associated with an explosive growth in the microbial population, which consumes plant nutrient ions that are needed for building new cells. The decline in carbon dioxide production occurs because the microbes have consumed most of the readily decomposable high energy organic materials. The rate of carbon dioxide production and microbial population is dramatically reduced simultaneously.
As the microbial activity declines, the dead cells are destroyed, releasing nutrients in plant available inorganic form. Nitrogen is released as ammonium (NH4+). Sulfur is released in a reduced form as sulfide (S2+). Most other nutrients are released in the ionic form (e.g. H2PO4-). The mineralization of large quantities of nitrate and sulfate signal the completion of the major microbial degradation process