What is a biogeochemical cycle?
A biogeochemical cycle is a cycle of a matter (such as nitrogen or phosphorus) in the environment.
A biogeochemical cycle include compartments (in water, in lithosphere, in atmosphere), forms (gas, adsorbed, soluble, etc.) and life span of materials (e.g. nitrogen or phosphorus).
You can see details of nitrogen cycle:
A detailed answer on biogeochemical cycle can be found at: