The phosphorus cycle, unlike sulfur, carbon and water cycles, does not contain a gaseous phase. Passing through liquid and solid phases, the phosphorous cycle begins essentially from the soil and ends in the soil.
During the weathering of rocks by rainwater, flood, and other forms of runoff, part of the constituent phosphates of rocks are washed down into soils, rivers, streams and oceans.
Thus, the phosphates present in the plants through irrigation or through natural absorption of soil water, become part of the constituents of growing plants in the ecosystem. Plants, however, do not remain unused; they are consumed by herbivorous animals, as fodder and by man as herbs and vegetables. As a result, phosphorous, in the form of the phosphates originating in the weathering of rocks, enters into the bodily systems of herbivorous plants and animals, and unites in the process of transformation or metabolism to form other chemical compounds of phosphorous. The process does not end there, as both man and animal pass out waste matter in the form of urine and excreta (Joiner, 75). Man and animals pass these out into or onto soil, or into lavatories (from lavatories, these wastes ultimately arrive in the soil). Alongside these process is the decomposition of dead plant or of animal and human bodies, which releases already absorbed or digested phosphates ( Mariah, 95). Thus, converted phosphates enter the soil, and close the cycle there.
The above description is basically the process of the phosphorous cycle. ...