The majority of Earth's atmosphere contain 78% is nitrogen, The Nitrogen cycle is the geochemical cycle in which nitrogen is converted into multiple chemical forms. Nitrogen cycle occurs in terrestrial and marine ecosystem. Nitrogen can be converted through both biological and physical process. The processes that are involved in nitrogen cycle are fixation, ammonification, nitrification, and denitrification.
There is limited amount of nitrogen that is useful but increase of fossil fuel combustion, use of artificial nitrogen fertilizer have dramatically increased the amount of nitrogen in nitrogen cycle.