Biogeochemical Cycle:
The movement of nutrient elements through the various components of an ecosystem is called nutrient cycling or biogeochemical cycle.
Nutrient cycles are of two types
(a) Gaseous
(b) Sedimentary
The reservoir for gaseous type of nutrient cycle e.g., nitrogen and carbon cycle is atmosphere. Earth's crust is the reservoir of sedimentary cycle (e.g., sulphur and phosphorus cycle).
The function of the reservoir is to meet with the deficit, occuring due to imbalance in the rate of influx and efflux. Environmental factors, e.g., soil, moisture, $\mathrm{pH}$, temperature, etc., regulate the rate of release of nutrients into the atmosphere.
Phosphorus Cycle
Phosphorus cycle is an example of sedimentary nutrient cycle, it moves from land and get sedimented at the bottom of the seas, then back to land again.
The natural reservoir of phosphorus is earth's crust. Rock contains phosphorus in the form of phosphates. Phosphates enter streams, rivers and then to oceans due to weathering and soil erosion.
Sea floor is uplifted with great movements of the crustal plates and phosphates become exposed on the drained land surfaces. Here, weathering over long periods of time releases phosphates.
Minute amount of these phosphates dissolve in soil and are absorbed by the roots of the plant, phosphate is obtained by herbivores and other animals from plants when they consume plants as their food.
The waste products and the dead organisms are decomposed by phosphate-solubilising bacteria that release phosphorus.