Phosphorus Cycle Steps

Sunday, September 6, 2020

Phosphorus Cycle

Along with the water cycle, the carbon cycle, and the nitrogen cycle, the phosphorus is another biogeochemical cycle that is essential for life on earth.

A biogeochemical cycle is a pathway by which a chemical substance moves through biotic and abiotic compartments of Earth.

Although phosphorus is not found in the atmosphere, it still plays a very important role in plants and animals on Earth.  

Phosphorus is essential for plant and animal growth, as well as the health of microbes inhabiting the soil.

Phosphorus cycle

Phosphorus is very important for the production of DNA by forming the backbone of DNA and RNA and makes up the cell membrane.

The phosphorus cycle is a slow process and involves four key steps.

Step 1. Weathering

Phosphorus is found in rocks. Weathering along with rain breaks down the phosphorus in rocks and it travels to the soil and into water sources.


Step 2.  Absorption by Plants and Animals

Once in the soil, plants, fungi, and microorganisms are able to absorb phosphorus and grow. Some of it also makes its way to the ocean and freshwater and animals are able to drink this water and plants absorb the water along with the phosphorus.

Animals then eat the plants and the phosphorus moves into the animals. 

absorption by plants

Step 3. Return to the Environment via Decomposition

Animals excrete waste and decomposers are able to use the phosphorus in the waste material. Furthermore, when the plants and animals die the bacteria may convert the organic phosphorus into inorganic phosphorus in a process called mineralization.

Step 4. Sediments to rocks

Some of the phosphorus gets buried in settlements which over time becomes rocks and the cycle continues. Some of the phosphorus in the soil gets washed to the ocean where a similar process takes place.

Plants and animals in the ocean absorb the phosphorus, die and decompose, and some of the phosphorus ends up as sediments in rock.

Humans have had a significant impact on the phosphorus cycle. Fertilizers containing phosphorus add to the phosphorus levels in the soil. This helps plant growth however, when levels of phosphorus are too high, the overabundance of plant nutrients serves to drive the excessive growth of algae. When these algae die or form algae blooms, they can be toxic to the plants and animals in the ecosystem.

Related Links

Carbon Cycle

Rock Cycle

Reasons for the Seasons


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