What is Nutrient Cycling? And Why is it Important? 

Nutrient cycling is Earth’s way of moving natural and chemical substances through the environment. You can refer to the nutrient cycle as an energy flow. It helps the soil, plants, and other living organisms get the required nutrients. 

In this article, you will learn about the meaning of the nutrient cycle and its importance to the environment. We will also discuss different nutrient cycles like the nitrogen, oxygen, and water cycle.

Table of contents:

What Is The Nutrient Cycle? 

The ecosystem and living organisms' cells have six primary elements: oxygen, hydrogen, carbon, nitrogen, phosphorus, and sulfur. The nutrient cycle, or the biogeochemical cycle, is the movement of these nutrients from the environment into plants, animals, and humans and recycling it again.

The primary elements mentioned earlier move through the earth’s ecosystem—atmosphere, water bodies, soil, and living organisms. It recycles and reuses these elements to maintain order. These nutrients fuel life, recycling themselves in a closed loop. 

Nutrient cycles occur through living and nonliving organisms using chemical, biological, and geological processes. However, soil microbes are an essential element that helps foster nutrient cycles. Soil and its microbes help break down organic matter and release nutrients into a processing cycle, changing forms until they return to their original state.

Importance of Nutrient Cycling

The nutrient cycle is vital because it involves the movement and transformation of most nutrients necessary for growing plants and maintaining the food web. The nutrient cycle plays a significant role in maintaining soil fertility. 

Plants absorb organic nitrogen, carbon, and other nutrients into their cells and tissues. They return these nutrients to the soil when the leaf litter, branches, and other organic matter they shed decompose. Nutrient cycling is the peak of nutrient management and is great for organic farming. 

Carbon cycling helps maintain life on Earth. Significant imbalances in the carbon cycling process will make Earth uninhabitable. There has to be a constant movement and exchange of CO2 because excess carbon in an area puts the environment at dangerous risks of climate change and global warming. The planet becomes too hot and damages its living organisms. 

The nitrogen cycle is crucial because the primary producers, plants and photosynthetic bacteria, need nitrogen molecules to convert sunlight into energy. Chlorophyll requires a lot of nitrogen to process photosynthesis. Less nitrogen means less chlorophyll, which reduces energy and nutrients necessary for growth.

Without the oxygen cycle, many life forms, including humans, wouldn’t survive on Earth. It is responsible for the evolution of living beings. Decreased oxygen content in nutrient cycling leads to health problems¹.

Types of the Nutrient Cycles

Nutrient cycling involves chemical elements like:   

• Carbon cycle 
• Oxygen cycle
• Nitrogen cycle
• Phosphorus cycle  
• Water cycle 

Let’s discuss the processes of these cycles.  

Carbon Cycle

Carbon is one of the most critical elements in the physical environment. It is essential to all life forms because they cannot survive without converting carbon dioxide in the atmosphere to carbon-based organic molecules of living organisms.

The carbon cycle recycles carbon at varying rates in different areas of the environment. It involves long-term carbon cycling through geologic processes and rapid carbon exchange among organisms in the earth’s atmosphere, surface, and crust. 

This nutrient cycling occurs everywhere because carbon is stored in inorganic mineral nutrients in crustal rocks, the oceans, and the atmosphere. Carbon dioxide cycles faster between the atmosphere and organisms. Using photosynthesis, plants and marine organisms convert carbon dioxide into organic carbon.

This conversion helps them produce other organic molecules like starch, lipids, and proteins, which are necessary for the survival of animals and other living organisms that feed on them. Then, they break down the organic molecules in aerobic cellular respiration, which consumes oxygen and releases energy, water, and carbon dioxide. 

The carbon dioxide released from the process returns to the atmosphere, where the cycle repeats itself. Carbon also recycles itself by decomposing living organisms and other organic matter.  

The decomposition process involves bacteria and fungi breaking down complex organic compounds. The bacteria and fungi then release carbon dioxide back into the atmosphere. Photosynthesis and cellular respiration go hand in hand in cycling carbon. Besides burning fossil fuels, these are the only ways to process CO2 and return it to the atmosphere. So, a significant change in any of these processes influences the amount of carbon in the air.

Oxygen Cycle

The oxygen cycle is also part of the nutrient cycle. It is the movement of oxygen’s various forms through organic materials. Although it is dependent on the carbon cycle, it can function independently. 

These biogeochemical cycles depend on one another because the carbon cycle provides the oxygen for the cycle. In contrast, the oxygen cycle returns carbon dioxide to the atmosphere. Plants and animals use oxygen to breathe/respire and return carbon dioxide to the air and water. 

The next step in the process is for plants and algae to use the released carbon to produce carbohydrates through photosynthesis, releasing oxygen as their by-product. And the cycle repeats itself over and over again. Water bodies are responsible for the primary production of oxygen. Scientists state that our oceans’ algae can return 90% of the oxygen used.

Nitrogen Cycle

The nitrogen cycle is crucial to the survival of living beings and organisms. Nitrogen is necessary for healthy plant growth and seed development. About 78% of the gas in the air is nitrogen. Still, atmospheric nitrogen is not helpful to organisms in its gaseous form. It becomes useful when nitrogen-fixing bacteria transform it.

There are various steps in the nitrogen cycle. These steps are: 

• Nitrogen fixation
• Nitrogen assimilation 
• Ammonification
• Nitrification
• Denitrification 

Nitrogen fixation is the process of converting atmospheric nitrogen into ammonia. Ammonia then becomes ammonium, which enters the soil and water reservoirs. The two types of nitrogen-fixing bacteria are non-symbiotic bacteria and symbiotic bacteria. The non-symbiotic bacteria are cyanobacteria, nostoc, and azotobacter. In contrast, the mutualistic bacteria include rhizobium, a bacteria common to leguminous plants.

The bacteria enter the root hairs of host plants, multiply, and influence the formation of root nodules. They enlarge plant cells and bacteria in close association. They convert atmospheric nitrogen to ammonia, which the plant uses for development. 

Nitrates and ammonia from nitrogen fixation assimilate into tissue compounds of algae and higher plants, which animals eat. After assimilation, the animals convert them to the mineral nutrients they need. Ammonification begins by decomposing living organisms and their waste products.

Depending on the soil conditions, the ammonia produced can leave the soil or be changed into other nitrogen compounds. Nitrification is converting ammonia in soil into nitrates by nitrifying bacteria. At the same time, denitrification is the process of denitrifying bacteria and metabolizing bacteria. 

The denitrifying bacteria is more active in water-logged areas. It breaks down nitrates in the soils, converting them to atmospheric nitrogen. The nitrogen cycle is a never-ending process of nitrogen conversion that sustains life and the food chain.

Phosphorus Cycle

Next on nutrient cycling is phosphorus, a significant component of nucleic acid and phospholipids. It is part of the components that support our bones and the growth of aquatic organisms. In nature, it exists as a phosphate ion. 

Phosphorus is one of the most limited nutrients in nutrient recycling. Still, it is one of the most essential nutrients involved in energy flow and the passage of genetic information in all cells' DNA. Weathering, mining, and leaching release most of the earth’s phosphorus in rock and sedimentary deposits.

Phosphorus enters freshwater and terrestrial ecosystems’ food chains through predators, parasites, plants, and surface runoff. However, most phosphorus enters oceans, where it circulates or settles. We bring it back to land through fishing and seabird excretion. Just like other nutrient cycles, the decomposition of organic material releases phosphates for recycling.

Water Cycle

Water is another crucial aspect of the nutrient cycle. It is the continuous water movement through the earth and its atmosphere, using the sun's energy to move water from the earth’s surface to the atmosphere and vice versa. 

Many processes are involved in the hydrological cycle, but the crucial ones are evaporation, transpiration, precipitation, condensation, and runoff. Evaporation is the transfer of water from the earth’s surface to the air by converting water in its liquid state into water vapor, a gaseous state.

Evaporation is affected by factors like humidity, temperature, and solar radiation. Sublimation directly converts a solid water state (snow and ice) to vapor. At the same time, transpiration refers to the evaporation of water through pores or stomata in plant leaves. Condensation is the transformation of vapor to a liquid state. 

Condensation occurs when different forms of air mass temperatures mix. It is through condensation that precipitation happens. Once the different air mass temperatures mix, rain falls, leading to surface runoff.

Conclusion  

Humans and other organisms benefit significantly from the nutrient cycle. Although living organisms store substantial amounts of nutrients, nature helps us recycle these nutrients so we don’t empty the reservoir or cause imbalances. The nutrient cycle is the backbone of the earth and its ecosystem.