The nitrogen cycle is a repeating cycle of processes during which nitrogen moves through both living and non-living things: the atmosphere, soil, water, plants, animals and bacteria. In order to move through the different parts of the cycle, nitrogen must change forms. The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmosphere, terrestrial, and marine ecosystems. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification.
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