How does phosphorus cycle begin?

The water, carbon, nitrogen, and sulfur cycles all include at least one phase in which the element is in its gaseous state; very little phosphorus circulates in the atmosphere because at Earth's normal temperatures and pressures, phosphorus and its various compounds are not gases. The largest reservoir of phosphorus is found in sedimentary rock. The phosphorus cycle differs from the other major biogeochemical cycles in that it does not include a gas phase, though small amounts of phosphoric acid (H3PO4) may find their way into the atmosphere and contribute—in some cases—to acid rain.

The phosphorus cycle starts in these rocks; when it rains, phosphates are carried out of the rocks (via weathering) and end up in soils and water; plants absorb the phosphate ions from the soil; phosphates then go from plants to animals through the process of herbivores eating plants and carnivores eating plants or herbivores; in the end, the phosphates absorbed by animal tissue through consumption return to the soil through excretion of urine and feces, as well as from the final decomposition of plants and animals.

The phosphorus cycle begins with the weathering of rocks containing phosphate minerals, which releases phosphorus into the soil.