All You Need To Know About Nitrogen Cycle!

All you need to know about Nitrogen Cycle!
Nitrogen, scientifically known as N, is one of the most abundant and essential elements of our ecosystem and atmosphere. Why? Because it is the primary building block of DNA for every living thing, even plants and animals. Nitrogen is everywhere; in the soil, in the water, and in the air.

Though nitrogen is essential, just like every other thing, its excess is also wrong. Plants will definitely rot if they are not getting enough nitrogen, but even too much of it can hurt them and pollute the air. That is why we need to understand the nitrogen cycle (how nitrogen moves in an endless cycle) to protect our plants and atmosphere from damage and toxicity.

Are you confused? Don't be. In this post, we are going to share every teeny tiny detail about the Nitrogen Cycle, from its definition to stages to everything. Keep Reading; it will get interesting!

Definition of Nitrogen Cycle

Before diving into the complex and essential details, let's go through the primary and scientific definition of the Nitrogen Cycle:

“Nitrogen Cycle is a biogeochemical process which transforms the inert nitrogen present in the atmosphere to a more usable form for living organisms.”

But, What Exactly Is Nitrogen Cycle?

Yes, we know what nitrogen is and the basic definition of the nitrogen cycle too. But the question is, what exactly Nitrogen Cycle is? Don't worry, we will explain you.

The nitrogen cycle is a repeated cycle of different processes and stages of how nitrogen moves from living and non-living things, and in what forms. These living and non-living things include soil, atmosphere, water, bacteria, plants, and animals.

Moreover, there are two forms of nitrogen: Inorganic and organic nitrogen. Organic nitrogen is found in living things and organisms that they consume through food. While on the other hand, the inorganic one is found in the atmosphere for plants.

Here are a few forms of how nitrogen exists for better understanding:

  • Atmospheric Nitrogen: Nitrogen gas (N2)
  • Soil: Nitrogen Oxide (NO) and Nitrogen Dioxide (NO2)
  • Fertilizer: Ammonia (NH3) and Ammonium Nitrate (NH4NO3)

As we have briefly mentioned above, Nitrogen undergoes different types of processes to maintain a balance to protect our atmosphere and ecosystem, and that is what we call the Nitrogen Cycle. There are a total of 5 stages of the nitrogen cycle; Nitrogen Fixation, Nitrification, Denitrification, Assimilation, and Ammonification.

Let's go through these processes in detail now!

Stages of Nitrogen Cycle

As promised, we are explaining the whole process and stages of the nitrogen cycle below. Read on!

Stages of Nitrogen Cycle

Nitrogen Fixation

Nitrogen Fixation is the first stage and step of the Nitrogen cycle where the atmospheric nitrogen (N2) is converted into the usable form, known as, ammonia (NH3). In simpler words, the nitrogen starts moving from the atmosphere to the soil. This process mainly happens through precipitation.

After this process, the nitrogen goes through a lot of changes which results in the separation of two nitrogen atoms. After separation, one of those two nitrogen atoms combines with hydrogen and forms another ammonia, known as NH4+.

Furthermore, the whole process of nitrogen fixation is carried out by Diazotrophs, symbiotic nitrogen-fixing bacteria. Apart from this, other nitrogen-fixing bacteria like Azotobacter and Rhizobium also help in the Nitrogen Fixation process. How? Because they contain a nitrogenase enzyme that can help in combining hydrogen and nitrogen to form ammonia.

You can perform the nitrogen fixation process and form ammonia with the help of atmospheric fixation; with the help of high temperature, lightning, and high-pressure condition. Moreover, you can also manufacture ammonia using man-made resources and industrial fixation and processes.

Don't know what Atmospheric fixation and Industrial fixation are? Yes, we had an idea. These are two of the types of the Nitrogen fixation process. To better understand, let's go through these types in detail!

Types of Nitrogen Fixation

There are a total of 3 types of Nitrogen Fixation:

Atmospheric Fixation:

Atmospheric fixation is a natural occurrence and type of nitrogen fixation. Here, the nitrogen breaks down into nitrogen oxides with the help of lightning energy. The plants then use these nitrogen oxides.

Industrial Nitrogen Fixation:

Unlike the natural atmospheric fixation, Industrial Nitrogen is a man-made alternative. It helps in the nitrogen fixation process with the help of ammonia. This ammonia is produced by combining hydrogen and nitrogen. The result we get is often in the form of urea, a fertilizer for plants.

Biological Nitrogen Fixation:

You know that plants and animals can't use nitrogen directly from the air, right? Because that is unusable. Nitrogen needs the blue-green algae and Rhizobium bacteria to become usable. This is what biological nitrogen fixation does, fixing the unusable nitrogen through the microbes and making it usable for plants and animals.


In the nitrification process, we convert the ammonia into nitrates with the help of bacteria present in the soil. The nitrification process is essential because ammonia is naturally toxic to plants. Therefore, it is important to convert it first.

In this process, the ammonia is oxidized with the help of Nitrosomonas bacterium, the form of bacteria. After oxidizing the ammonia, small nitrites are formed, which are further converted into nitrates. This is done with the help of a Nitrobacter.

Here is the scientific form of this process and reaction:

2NH4+ + 3O2 → 2NO2– + 4H+ + 2H2O
2NO2– + O2 → 2NO3–


Assimilation is the third stage of the nitrogen cycle. At this stage, the nitrogen is converted into a consumable form. This process is carried out by incorporating the NO3 and ammonia from the nitrogen fixation and nitrification process. The plants start consuming the nitrogen compounds such as ammonia, nitrate ions, nitrite ions, and ammonium ions with the help of their roots. All these nitrogen compounds play an essential role in building plant proteins. After this process, the nitrogen cycle enters the food chain when consumers start eating those plants.


After assimilation, we get organic nitrogen in multiple forms; proteins, nucleic acids, and amino acids. Ammonification is the process of conversion of that organic nitrogen into ammonia. When the nitrogen turns back into ammonia, it is again available for nitrification or assimilation.
In another scenario, when the plants and animals die, all the nitrogen present in them goes back to the soil. Then, that nitrogen is converted into ammonium with the help of decomposers like bacteria and fungi. The ammonia produced can further be used for various biological processes.


Denitrification is the final stage of the nitrogen cycle, and this process is only performed during the absence of oxygen. The ideal place for this process is deep in the soil or near water. In denitrification, the nitrogen compounds are sent back to the atmosphere by converting the nitrate (NO3-) into simple Nitrogen gas (N). Also, this process is done with the help of denitrifying bacteria; Pseudomonas and Clostridium.

Nitrogen Cycle and Marine Ecosystem

We know how the nitrogen cycle works in terrestrial ecosystems, however, have you ever wondered how it works in the marine ecosystem? Don't worry; the nitrogen cycle process is almost the same for both ecosystems; there is just one minor difference. The terrestrial ecosystems use the normal bacteria, but marine ecosystems use marine bacteria found in the ocean.

The marine nitrogen cycle also occurs with the help of several biogeochemical transformations. The compounds containing nitrogen drop down into the ocean and take the shape of sedimentary rocks. According to previous studies, these nitrogen sedimentary rocks in the ocean were a great source of nitrogen back in time, but now, scientists think that the nitrogen from these rocks is released back to the plants.

The importance of the Nitrogen Cycle

Now that we know how the nitrogen cycle works, it is time to understand how important the nitrogen cycle is for terrestrial ecosystems. Here are a few points for you:

  1. It allows the plants to synthesize coming out from the nitrogen-containing compounds.
  2. The nitrogen cycle helps in converting the unusable nitrogen gas into usable one for plants and animals with the help of different biochemical processes.
  3. In ammonification, the nitrogen cycle helps to clear up the matter and waste of dead plants and animals by decomposing them. This is an important and beneficial factor for the betterment of our environment and atmosphere.
  4. The nitrogen cycle helps in releasing nitrites and nitrates into the soil. These two compounds enrich the soil with nutrients for better cultivation.
  5. Nitrogen gas is indeed an integral component, and it is responsible for forming many vital compounds and biomolecules.

Is Nitrogen Cycle Crucial for Life?

If you want to maintain productive terrestrial ecosystems with a balanced amount of nitrogen, then yes, the nitrogen cycle is extremely crucial. All the biomass and plant production of our ecosystem relies on the availability of nitrogen. Moreover, the nitrogen cycle helps us understand the relationship between plants and soil. Having an understanding of this concept helps you make better decisions about cultivation, how to grow crops, and when and where to grow them. Additionally, an understanding of the nitrogen cycle will help you clean your environment clean and reduce pollution. How? By controlling the amount of fertilizers in the soil.
If there is not enough nitrogen in the atmosphere, the plants will be hungry and deteriorated. Therefore, scientists and farmers need to make sure that living organisms are never deprived of nitrogen. 


Nitrogen is an abundant part of our system, but keep one thing in mind; plants and animals can't use it unless it is converted into nitrogen compounds. Also, the nitrogen cycle is extremely crucial to maintaining a balanced level of nitrogen in our ecosystem. This is a never-ending cycle, and it is meant to repeat continuously to keep the atmosphere clean, healthy, and balanced.

If you still have any confusion related to the nitrogen cycle, you can always request us for a professional tutor. Our highly experienced tutors will make all your confusion and misconceptions go away.
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Frequently Asked Questions

Why is nitrogen important?
Nitrogen is extremely important for life, whether plants, animals, or humans. It is an essential compound to perform several biological processes of the human body. For example, amino acids contain nitrogen; and amino acids are super beneficial for different components of the human body like muscles, skin, hair, and tissues.
Why do plants require nitrogen?
Nitrogen contains chlorophyll; an important component for the betterment and growth of plants. Chlorophyll helps the process of photosynthesis and prevents plants from abnormalities, stunted growth, and disorders.
What are the 5 stages of the nitrogen cycle?
The 5 stages of the nitrogen cycle are as follows:
  1. Nitrogen Fixation
  2. Nitrification
  3. Assimilation
  4. Ammonification
  5. Denitrification
What do nitrifying bacteria do?
Nitrifying bacteria are the smallest type of aerobic. Their main function is to convert ammonia into nitrates.
Which part of the plant is involved in nitrogen fixation?
The plant's root systems are mainly involved in the process of nitrogen fixation.
Is there any difference between the nitrogen cycle of terrestrial ecosystems and marine ecosystems?
The only difference is that marine ecosystems use marine bacteria in their nitrogen cycle. Other than that, the overall function of the nitrogen cycle stays the same in both scenarios.
What happens if you interrupt a nitrogen cycle?
If a nitrogen cycle is interrupted somehow in the future, there are chances of acid rain. That acid rain can further lead to the death of all plants and animals.
What two things can disrupt the nitrogen cycle?
The nitrogen cycle can be disturbed by these two things:
  1. Fossil Fuels.
  2. Adding nitrogen to the fertilizers.

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