Nitrate Nitrification

Nitrification is an aerobic microbial process by which specialized bacteria oxidize ammonium to nitrite and then to nitrate. Nitrification is a very important part of the nitrogen cycle, because for most plants nitrate is... 

In addition to the oxidising of ammonia to nitrites and nitrates (nitrification), there also goes on a reverse process (denitrification) whereby nitrites and nitrates are destroyed by the action of certain organisms, e.g., a nitrate is converted directly into nitrogen, the final result being shown by some such end equation such as this —... 

Nitrification in wetlands is restricted to aerobic zones of soil and water column or under drained soils conditions, where ammonium is oxidized to nitrate. Nitrification reaction supports denitrification by supplying heterotrophs with nitrate as their electron acceptor. In a broader sense, nitrification is defined as the conversion of organic or inorganic compounds from reduced state to a more oxidized state. Three groups of microorganisms are capable of oxidizing ammonium under aerobic conditions ... 

In the process of ammonification, hydroxylamine (NH2OH) is an important intermediate in two directions, denitrification direct to ammonium as well as the oxidation of ammonium to nitrate (nitrification). As long as nitrogen remains in its reduced form (NH4), it remains in the local environment because of its affinity for soil absorption and its rapid uptake by biota. NH4 is in equilibrium with NH3, which can escape to the atmosphere, depending on pH, temperature, soil moisture, soil type and atmospheric NH3 partial pressure. The equilibrium between emission and deposition (gas uptake) is called the compensation point, similar factors control the emission/dry deposition of NO. 

Ammonia is also produced from burning of coal and bacterial decomposition of proteinaceous organic matter. Conversion of ammonia to ammonium salts will occur rapidly both in the atmosphere and in the soil but will result in less acidity of the soil. It is not known to what extent ammonia reduces excess greenhouse gases such as carbon dioxide in the atmosphere to form ammonium carbamate. Microbial assimilation of ammonium compounds consumes alkalinity of the soil as well as converting ammonium ions to nitrate. Nitrification is carried out by many aerobic bacteria. Nitrification is pH sensitive. Denitrification, which is an anaerobic process, is also pH sensitive. 

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