1. The natural reservoir of phosphorus is rock in the form of phosphates.

2. Minute quantities of phosphates get dissolved in the soil solution during weathering of rocks.

3. Phosphates enter the plants through their roots and then the food chain.

4. The organic wastes and dead organisms are decomposed by phosphate-solubilising bacteria, which release phosphorus back in the soil.

5. The atmospheric input of phosphorus through rainfall or gaseous exchange of phosphorus between organisms and environment, is negligible.

Phosphorus Cycle