Cycling Phosphorus

Phosphorus (P) is another one of the essential elements that cycle through the ecosystem. It is an element that is found in the ground and then taken up by plants and animals. Phosphorus starts its existence as phosphate ions (PO4) in the rocks of the world. When it rains, the phosphates and other minerals are removed from the rocks and distributed in soils and the water all over the planet.

Plants Need It

Plants on land take in the inorganic (compounds without carbon) phosphorus compounds from the soil. The phosphorus atoms are then incorporated into many organic compounds that are used in cells. Animals can get their phosphorus by eating plants or drinking water. Algae and water plants are able to absorb the ions from the water. Unlike carbon and nitrogen, the phosphorus cycle is not a true cycle. There is a great deal of phosphorus lost.

Losing The Element

Phosphorus has a tendency to wind up at the bottom of the ocean. Once at the bottom, the phosphate ions are lost to the world. Sometimes the phosphates are found in runoff water and go to the bottom and sometimes human poop contains phosphate and those phosphates are returned to the ocean. The problem is that all usable phosphorus sources are on the surface The atoms are useless once they reach the bottom of the ocean. Slowly but surely the surface of the Earth is running out of easy places to find phosphorus.

Elemental Concern

Why is there a sudden concern? Phosphorus only gets into the soil by the weathering process on rocks. When plants die in the natural world, the phosphates return to the soil. In farming, the crops are taken away and then over many years the soil runs out of phosphorus compounds. We have created a situation where we must artificially replenish the nutrients in the land. Phosphorus is heavily used in the farming industry and fertilizers filled with phosphates are used all over the world to help plants grow.

Next page on the biogeochemical cycles.
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