Natural reservoir of phosphorus is

The phosphorus cycle is a sedimentary cycle. Phosphorus is a major constituent of nucleic acids, biological membranes, and the cellular energy transfer system. Many animals need it to make teeth, bones, and shells.

The natural reservoir of phosphorus is rock, which contains phosphorus in the form of phosphate. When rocks are weathered, a minute amount of these phosphates get dissolved in the soil solution. These are absorbed by the roots of the plants.