Nitrification is the microbial process whereby ammonia is oxidized to nitrite and nitrate.
In general, this processs is detrimental to agriculture where large amounts of ammonia or urea-based fertilizers are applied to croplands. The nitrates that are formed are readily leached from the soil, leading to eutrophication of surface waters and contamination of ground waters, which often serve as a source of water for human consumption. Furthermore, nitrate and nitrite are substrates for denitrification, which results in their loss from the soil in gaseous form. The enzyme that initiates nitrification ammonia monooxygenase. Despite the importance of this enzyme, our knowledge of ammonia monooxygenase at the molecular level is meager.