The main reservoir or storage location for phosphorus in the phosphorus cycle is the Earth's crust. Phosphorus minerals, such as apatite, make up a significant portion of the Earth's crust and serve as the primary source for phosphorus. Over time, weathering processes release phosphorus from these minerals, which then becomes available for uptake by plants and other organisms. Phosphorus can cycle between the Earth's crust, soil, water bodies, and living organisms, but the largest amount of phosphorus remains stored in the Earth's crust.
