*nitrification*

n. [ Cf. F. nitrification. see Nitrify. ] 1. (Chem.) (a) The act, process, or result of combining with nitrogen or some of its compounds. (b) The act or process of oxidizing nitrogen or its compounds so as to form nitrous or nitric acid. [ 1913 Webster ]

2. A process of oxidation, in which nitrogenous vegetable and animal matter in the presence of air, moisture, and some basic substances, as lime or alkali carbonate, is converted into nitrates. [ 1913 Webster ]

☞ The process is going on at all times in porous soils and in water contaminated with nitrogenous matter, and is supposed to be due to the presence of a bacteria, such as members of the genus Azotobacter, formerly called nitrification ferments. In former times the process was extensively made use of in the production of saltpeter. [ 1913 Webster +PJC ]