Explanation

Ammonia produced by the degradation of manures and organic matter may not be available to plants because it is readily leached from soil. It is converted to nitrate with the help of certain microorganisms, i.e., called nitrification (the used bacteria, nitrifying bacteria). $2NH_{3} + 3O_{2} \rightarrow 2NO_{2}^{-} + 2H^{+} + 2H_{2}O$ $2NO_{2}^{-} + O_{2} \rightarrow 2NO_{2}^{-}$ Ammonia is first oxidized to nitrite by the bacteria Nitrosomonas and/or Nitrosococcus. The nitrite is further oxidized to nitrate with the help of bacterium Nitrobacter.