Nitrification is the process in which ammonia is converted into nitrite and then to nitrate by nitrifying bacteria. It is an aerobic process and performed by chemoautotrophic bacteria.
Nitrosomonas and Nitrococcus oxidise ammonia to nitrite.
[tex]2NH_3 + 3O_2 → 2NO_2^– + 2H^+ + 2H_2O[/tex]
Nitrite is further oxidised to nitrate by Nitrobacter.
[tex]2NO_2^– + O_2 → 2NO_3^–[/tex]
Nitrate is absorbed by plants and utilised.
