NITROGEN CYCLE

(Ecology) The circulation of Nitrogen in nature, consisting of a cycle of chemical reactions in which atmospheric nitrogen is compounded, dissolved in rain, and deposited in the soil, where it is assimilated and metabolized by bacteria and plants, eventually returning to the atmosphere by bacterial decomposition of organic matter. Also, a model illustrating conversion of nitrogen from one form to another through a combination of biological, geological, and chemical processes. The process is continuous, with atmospheric nitrogen, N2, being converted to forms usable by biota and then ultimately returning to the atmosphere as N2.