Phosphorus Inputs to the Cycle

The phosphorus that reaches the soil can have four different sources:

Atmospheric deposition

Atmospheric deposition consists of the small particles (dust) that are transported by the wind and land on top of the soil. Dust particles contain phosphorus and it can be incorporated in the soil.

Phosphorus minerals

There are many different rocks that contain phosphorus in their structure. Rocks are the biggest reservoir of phosphorus in the Earth crust. This phosphorus can be available for photosynthetic organisms due to weathering of the rocks, and this is the only process that creates "new" phosphorus and makes it available for organisms.

Organism residues

Another important input of phosphorus to the soil is the decomposition of corpses or debris from organisms. Corpses of organisms contain organic phosphorus compounds and when they decompose those compounds are released and available to be used by other organisms.

Fertilizer

Fertilizers are used to increase the concentration of nutrients in the soil. More information in Fertilization theory page.