Mineralization in soil science is the

decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...

(i.e.,

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

) of the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

s in organic matter, by which the nutrients in those compounds are released in soluble inorganic forms that may be available to

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...

s. Mineralization is the opposite of immobilization. Mineralization increases the

bioavailability In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. By definition, when a medication is administered intravenously, its bioavailability is 100%. Ho ...

of the nutrients that were in the decomposing organic compounds, most notably, because of their quantities,

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

, and sulfur. Whether the decomposition of an organic compound will result in mineralization or immobilization is dependent on its concentration proportionate to that of the carbon in the organic matter. As a rule of thumb, if the concentration of a specific element exceeds the needs of the decomposer for biosynthesis or storage, then it will mineralize.

Ratio of carbon to nitrogen

Whether

mineralizes or immobilizes depends on the

carbon-to-nitrogen ratio A carbon-to-nitrogen ratio (C/N ratio or C:N ratio) is a ratio of the mass of carbon to the mass of nitrogen in organic residues. It can, amongst other things, be used in analysing sediments and soil including soil organic matter and soil amendm ...

(C:N ratio) of the decomposing organic matter.R.G. McLaren & K. Cameron ''Soil Science: Sustainable production and environmental protection'' (2nd edition), Oxford University Press, 1996, In general, organic matter contacting soil has too little nitrogen to support the biosynthetic needs of the decomposing soil microbial population. If the C:N ratio of the decomposing organic matter is above circa 30:1 then the decomposing microbes may absorb nitrogen in mineral form as, e. g., ammonium or nitrates. This mineral nitrogen is said to be immobilized. This may reduce the concentration of inorganic nitrogen in the soil and thus the nitrogen is not available to plants. As

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

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.

References

{{Reflist Soil science Nitrogen

Ratio of carbon to nitrogen

See also

References