The main reservoir of phosphorus on Earth is found in sedimentary rocks, particularly in the form of phosphate minerals. These rocks are formed over geological time through the accumulation of organic matter and chemical processes that concentrate phosphorus. When weathering occurs, phosphorus gets released into soil, water bodies, and eventually can be taken up by plants. However, the majority of phosphorus is locked away in these sedimentary deposits, making them a crucial aspect of the phosphorus cycle.
In addition to sedimentary rocks, phosphorus is also present in smaller amounts in soil and living organisms. Unlike nitrogen, which has a significant gaseous component in the atmosphere, phosphorus does not have a prominent atmospheric form, relying heavily on terrestrial and aquatic ecosystems for its circulation.