Nitrogen Cycle

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Ammonification is the production of ammonia from organic ammonium-containing compounds. These compounds include; urea (from amino acid breakdown), proteins, nucleic acids and vitamins (food in faeces and dead organisms). Saprobiotic organisms, mainly fungi and bacteria (the decomposers in the diagram), feed on these materials, releasing ammonia which then forms, ammonium ions in the soil. 


Some bacteria obtain their energy through chemical reactions involving inorganic ions. One such reaction is the conversion of ammonium ions to nitrate ions. This is an oxidation reaction and so releases energy. It is carried out by free-living soil microorganisms called nitrifying bacteria. This conversion occurs in two stages:

  • Oxidation of ammonium ions into nitrite ions (NO2−)


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