<P> The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere . Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus - based compounds are usually solids at the typical ranges of temperature and pressure found on Earth . The production of phosphine gas occurs in only specialized, local conditions . </P> <P> On the land, phosphorus gradually becomes less available to plants over thousands of years, because it is slowly lost in runoff . Low concentration of phosphorus in soils reduces plant growth, and slows soil microbial growth - as shown in studies of soil microbial biomass . Soil microorganisms act as both sinks and sources of available phosphorus in the biogeochemical cycle . Locally, transformations of phosphorus are chemical, biological and microbiological: the major long - term transfers in the global cycle, however, are driven by tectonic movements in geologic time . </P>

What is the purpose of the phosphorus cycle