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]