Phosphorus Cycle

The phosphorus cycle is a natural phenomenon by which phosphorus cycles through the three components of the biosphere which are the hydrosphere, lithosphere, and atmosphere. The phosphorus cycle is a very gradual process. The phosphorus cycle steps include weathering, release of phosphates into soil and water, plant uptake, consumption by animals, and return to the soil through decomposition and waste.

Phosphorous is found in small quantities in soil and enhances the growth of the plant. In this article, we will discuss the phosphorus cycle process and steps with the help of a diagram.

What is Phosphorous Cycle?

Phosphorus Cycle Definition: The phosphorus cycle refers to the movement and recycling of phosphorus through the biosphere components.

Phosphorous moves in a cyclic manner in rocks, water, soil, sediments, organisms, and various sediments. This biogeochemical cycle is termed phosphorus cycle. The phosphorus cycle consists of several steps. It is mainly dependent on the type of rock but other environmental factors such as air and water also have a role to play in it. Phosphorous helps in the development of cells and further stores energy in the form of ATP i.e. Adenosine Triphosphate. If there is a lack of phosphorous in the soil it results in poor yield of the crops.

Phosphorus Cycle Diagram

The phosphorus cycle is easily understood with the help of a labelled diagram.

Steps of Phosphorous Cycle

The phosphorous cycle involves the following steps:

Weathering

• As weathering of rocks takes place by the action of rain or by acid-producing bacteria, it releases the phosphorous present in the rocks in the soil.
• This phosphorous is also carried down the mountains and slopes with the help of water.
• Phosphorous from these streams and rivers also reach oceans and gets deposited at the base of the oceans.
• Natural landforms such as volcanoes also result in the release of phosphorous from the inside of the Earth to the soil.
• The phosphorous in this step is in inorganic form.

Absorption by Plants and Animals

• The inorganic phosphorous that is present in the soil is consumed by the plants.
• Though the amount of phosphorus is not enough this is why phosphate fertilisers are added to the soil.
• These plants are then eaten by herbivores which are further eaten by carnivores and omnivores which leads to the passing of phosphorous to various animals.
• Aquatic plants get the required phosphorous from the bottom of the oceans where it is deposited in the form of sediments in the soil.
• Various symbiotic organisms also help in the release of oxygen from the soil to the plants.
• In the body of plants and animals, this inorganic phosphorous is then converted to organic phosphorous which makes up their DNA and helps them to perform various processes in the body.
• The phosphorous in animals is used for the formation of biomolecules and bones.

Return of Phosphorus Back to Ecosystem by Decomposition

When the plants and animals die, the organic phosphorous is again converted to inorganic phosphorous by the action of certain bacteria in the soil so that it is made available again for the use of plants and animals.

Importance of Phosphorus Cycle

The phosphorous cycle has a very significant role to sustain life on this Earth.

• The phosphorus cycle is responsible for the existence of life on this Earth. It ensures that the phosphorus concentration is maintained on the Earth and there is an equilibrium between the consumption of phosphorus from the environment and the release of phosphorus in the environment.
• The phosphorus cycle is responsible for the cycling of phosphorus from the environment to various organisms and back to the environment which ensures that organisms can carry out their basic life processes.
• There are certain elements in nature that exist as a compound formed with phosphorus. Thus phosphorus cycle also ensures that these elements also move from one state to another in the environment.
• In the absence of the phosphorus cycle, plants will not be able to make ATP which is their basic unit of energy, and thus no energy can be made by plants that could be further transferred to the other organisms. Thus life is impossible without phosphorus.
• Scientists can also study the characteristics of microorganisms that interact with phosphorus if they are well-versed in the process of the phosphorus cycle.

Availability of Phosphorous to Plants

A good amount of phosphorous present in the soil is not available for use by the plants. The availability of useful phosphorous to the plants depends upon various factors which are:

• Bacteria: The bacteria present in the soil are directly responsible to make the phosphorous available to plants. If the soil contains such bacteria then it will be rich in potassium that can be used by the plants.
• Adsorption of Phosphorous: Generally, the phosphorous present in the soil is adsorbed by the soil particles and is not available to plants for use. The release of this phosphorous takes place through the process of desorption.
• pH of the soil: Phosphorous can be used by plants if it is present in free form. If the pH of soil falls below 4 or becomes more than 8 then the free phosphorous starts to combine with other minerals to form compounds that make the phosphorous unavailable for use by plants.

In order to make the phosphorous available to plants, fertilizers are the most commonly used product. Fertilizers that are rich in phosphates are used to replenish the phosphorous content of the soil. It must be ensured that the pH of the soil is within the permitted limits to prevent phosphorous loss. Lime is generally used to reduce the acidity of the soil.

The phosphate from the soil and fields is carried by the rainwater to rivers and oceans which leads to excessive plant growth in these water bodies. This excessive plant growth leads to the eutrophication of water bodies.

Human Effects on Phosphorus Cycle

Various human activities such as the use of fertilizer in agriculture, eutrophication of water bodies, etc. lead to a change in the phosphorus cycle and the rate at which phosphorus cycles from one form to another. For example, the use of phosphorus fertilizers enriches the fertility of the soil but due to irrigation and heavy rains, this phosphorus from the fields reaches the water bodies such as rivers, streams, and canals which leads to excessive algae bloom in them leading to high rate of eutrophication and shortage of oxygen in the water which becomes harmful for the aquatic life.

Sometimes the phosphorus in human and animal wastes is not treated properly and discharged into water bodies which again raises the level of phosphorus in them. The improper water treatment by the municipality also leads to excess phosphorus remaining in the water which enters our bodies when we drink water and is harmful to us. Thus we need to be very careful while using phosphorus in an artificial way so that the ecological balance is maintained.

Conclusion: Phosphorus Cycle – Definition, Steps, Importance and Impact

In conclusion, the phosphorus cycle, a gradual process spanning the hydrosphere, lithosphere, and atmosphere, involves key steps such as weathering, plant uptake, and decomposition. This cycle sustains life by maintaining phosphorus concentrations, essential for energy production and DNA synthesis. Human activities like fertilizer use and improper waste management impact this cycle, highlighting the need for responsible stewardship to preserve ecological balance and prevent harmful effects on ecosystems and human health.

FAQs on Phosphorous Cycle – Definition, Steps, Importance and Impact

State any Two uses of Phosphorous.

Phosphorous is used in the manufacture of fertilizers and it is also used to make matchsticks.

How is Excess Phosphorus Harmful to Aquatic Life?

Excess phosphorus in water bodies leads to algal blooms which reduce the oxygen content in the water, thereby causing the death of aquatic organisms.

Why is Phosphorous Important for Humans?

Phosphorous is important for humans as it helps in the formation of teeth and bones. It also helps in DNA formation in humans.

What acts as a Natural Storehouse of Phosphorus?

Rocks act as a natural storehouse of phosphorus as the phosphorus cycle starts with the release of phosphorus from rocks to the soil and finally reaches back to the rocks by the process of lithification.