What is the Difference Between Nitrogen Cycle and Phosphorus Cycle

The main difference between nitrogen cycle and phosphorus cycle is that nitrogen is recycled in the nitrogen cycle while phosphorus is not recycled in the phosphorus cycle.  

The nitrogen and phosphorus cycles are two biogeochemical cycles important for the cycling of nutrients. They determine the flow of nutrients through organisms and the environment. 

Key Areas Covered

1. What is Nitrogen Cycle
     – Definition, Facts, Importance
2. What is Phosphorus Cycle
     – Definition, Facts, Importance
3. Similarities Between Nitrogen Cycle and Phosphorus Cycle
     – Outline of Common Features
4. Difference Between Nitrogen Cycle and Phosphorus Cycle
     – Comparison of Key Differences

Key Terms 

Nitrogen Cycle, Phosphorus Cycle

What is Nitrogen Cycle

The nitrogen cycle is the process where atmospheric nitrogen successively passes from air to the soil, organisms, and the atmosphere. The atmosphere is the primary nitrogen source, containing 78% nitrogen gas. But atmospheric nitrogen has limited availability for living organisms. Therefore, multiple chemical and biochemical processes convert nitrogen into compounds circulating in atmospheric, terrestrial, and marine ecosystems.

Figure 1: Nitrogen Cycle

The nitrogen cycle steps include nitrogen fixation, nitrification, denitrification, decay, and putrefaction. The nitrogen-fixing bacteria in the soil convert this nitrogen into ammonia, nitrite, and nitrates. Lightening is another process of nitrogen fixation. Plants absorb these nitrogen compounds to make proteins. Herbivores and carnivores consequently consume these proteins. Proteins are essential in making structures and as energy sources. Also, nitrifying bacteria’s breakdown of dead organisms releases nitrogen compounds back into the soil. These nitrogen compounds in the soil are released into the atmosphere by denitrifying bacteria.

However, human activities, including fossil fuel combustion, release nitrogen in wastewater and artificial nitrogen fertilizers dramatically later in the nitrogen cycle.

What is Phosphorus Cycle

The phosphorus cycle is a biogeochemical cycle that moves the phosphorus lithosphere, hydrosphere, and biosphere. However, the atmosphere is not essential in the phosphorus cycle because phosphorus compounds are mainly solid. Moreover, the phosphorus cycle is a prolonged process. The four steps of the phosphorus cycle include weathering, absorption by plants, absorption by animals, and the return to the environment through decomposition. Various weather conditions cause phosphorus to wash from rocks away into the soil. Organic matter in the ground absorbs phosphorus. Phosphorus also dissolves in water, and plants absorb phosphorus. But the amount of dissolved phosphorus in soil is less. Therefore, farmers must apply fertilizers as phosphorus is essential for plant growth. In aquatic ecosystems, undissolved phosphorus inhibits the growth of aquatic plants.

Figure 2: Phosphorus Cycle

Moreover, animals absorb phosphorus through the consumption of plants. When the plants and animals die, microorganisms decompose organic matter converting organic phosphorus into inorganic forms. This inorganic phosphorus again deposits on rocks and soil. Human activities, including the overuse of phosphorus fertilizers, impact the environment. 

Similarities Between Nitrogen Cycle and Phosphorus Cycle

• Nitrogen and phosphorus cycle are two biogeochemical cycles important for the cycling of nutrients through the environment and organisms.
• They determine the pathway of nutrients.
• Animals get both nitrogen and phosphorus through the food they eat.

Difference Between Nitrogen Cycle and Phosphorus Cycle

Definition

The nitrogen cycle refers to the series of steps by which nitrogen and its compounds are interconverted in the environment and living organisms, including nitrogen fixation and decomposition. In contrast, the phosphorus cycle refers to the biogeochemical cycle, moving phosphorus through the lithosphere, hydrosphere, and biosphere.

Recycling

Nitrogen is recycled in the nitrogen cycle, while phosphorus is not recycled in the phosphorus cycle.  

Occurrence

Nitrogen mainly occurs in the atmosphere, while phosphorus occurs in natural reservoirs.    

In the Ocean

Nitrogen is not lost in the ocean, while phosphorus is lost in the ocean.  

Conclusion

In brief, the nitrogen and phosphorus cycle are two biogeochemical cycles that occur on the Earth. They determine the flow of nutrients through organisms and the environment. The nitrogen cycle is the process by which nitrogen and nitrogenous compounds are cycled in living organisms and the environment. Nitrogen mainly occurs in the atmosphere. Organisms get nitrogen primarily through the food they eat. It is recycled in the nitrogen cycle. In comparison, phosphorus occurs in natural reservoirs and is lost in the ocean. However, it is not recycled in the phosphorus cycle. Therefore, the main difference between the nitrogen and phosphorus cycle is the recycling of nutrients through each cycle.  

References:

1. “Nitrogen cycle explained – definition, stages and importance.” BYJUS. 
2. “Phosphorus cycle – steps and importance of phosphorus cycle.” BYJUS. 

Image Courtesy:

1. “Nitrogen Cycle 2” By Johann Dréo – Own work (CC-BY SA 3.0) via Commons Wikimedia
2. “Phosphorus Cycle copy” By Welcome1To1The1Jungle at English Wikipedia – Own Work (CC-BY 3.0) via Commons Wikimedia