What is Nitrogen Cycle and Its Benefits to Life

Do you know the largest constituent of the atmosphere? Yes, nitrogen. This colorless and odorless element is found underground, in the water we use every day, and in the air we breathe. As much as 78% of the atmosphere is composed of the element nitrogen. So, do not be surprised if the element with the symbol N has various benefits for life.

Abundant on earth, then where did it come from? Nitrogen exists from a series of production processes called the nitrogen cycle or cycle. Check out the following explanation of the stages of the nitrogen cycle so you are not curious.

What is the Nitrogen cycle?

Nitrogen is an important substance that affects the body of organisms, including humans. However, most living things cannot ‘consume’ nitrogen directly. This is because nitrogen in the atmosphere is generally still in the form of N2 and has strong bonds that are difficult to react. There needs to be a change or combination of elements so that nitrogen can ultimately be useful for living things. According to 7activestudio Nitrogen Cycle

The nitrogen cycle moves through living and non-living things. Including the atmosphere, soil, water, plants, animals, and bacteria is what is called the nitrogen cycle. In essence, the nitrogen cycle is an iterative process that converts elemental nitrogen into other chemical forms through living and non-living things.

There are five stages of the cycle that nitrogen must go through in order for it to be utilized by many living things. The explanation of the cycle is as follows.

1. Nitrogen Fixation

Nitrogen Fixation

The first stage is nitrogen fixation. This stage is the process of ‘capturing’ nitrogen gas in the air. At the fixation stage, nitrogen gas will be captured directly by underground microorganisms that are diazotrophs ( RhizobiumAzotobacteraceae, and others).

Bacteria with diazotroph or nitrogen-fixing ability have nitrogenase enzymes, which are enzymes that can convert nitrogen gas into ammonia or NH3. This ammonia compound will then be converted by microorganisms into amino acids.

Gas nitrogen (N2) —> mikroorganisme —> NH3 (amonia) —> asam amino

The process of non-biological fixation also occurs through the help of energy that produces heat or high pressure, such as lightning and lightning. Nitrogen that interacts with lightning will react with oxygen and produce nitrogen oxides (NO) or nitrogen dioxide (NO2) compounds. Both can enter the ground through the medium of rain or snow.

2. Nitrification

The second step of the hydrogen cycle is nitrification. At this stage, the previously produced ammonia will be converted into nitrate. Nitrifying bacteria (bacteria that are able to synthesize nitrate from ammonia in an aerobic underground manner) play an important role in the nitrification stage.

As reported by nature.com, nitrification actually consists of two major processes. First, nitritation is the oxidation of ammonia to nitrite carried out by groups of bacteria of the genus NitrosomonasNitrosospira, and Nitrosococcus; and Archaea named Nitrosopumilus maritime. This process relies on the enzymes ammonia monooxygenase and hydroxylamine oxidoreductase.

NH3 + O2 + 2e- —> NH2OH + H2O —> NO2- + 5H+ + 4e-

The second is nitration which is the process of oxidizing nitrite compounds to nitrates by bacteria. In contrast to nitritation, nitration is carried out by bacteria of the genus Nitrospira, Nitrobacter, Nitrococcus, and Nitrospina.

NO2– + 0.5 O2 —> NO3–

Well, the nitrification process has changed the form of nitrogen captured by bacteria into nitrate. Nitrogen that has changed its chemical form can later be absorbed by plants.

3. Assimilation

The result of the nitrification process converts nitrogen gas that is difficult to decompose into compounds that are easily absorbed. This absorption process is called assimilation in the nitrogen cycle. Plants absorb nitrogen that has been processed through root hairs that are underground.

The assimilation process converts the nitrate produced in the previous step into nitrite ions and ammonium ions. Because the ion is polar, aka easily soluble in water, making nitrogen compounds that have gone through a series of processes more easily absorbed by plants.

Some plant species can assimilate nitrate to ammonium ion directly in nodules (root nodules). However, others need to include it in nucleic acids, amino acids and chlorophyll.

4. Ammonification


Plants that already contain nitrogen-derived compounds will be eaten by animals and humans. Thus, nitrogen compounds present in plants will also move to living things that eat them.

Well, when the plant-eating living thing excretes feces or dies, then the nitrogen that has been consumed will be converted back into ammonium (NH4+). The process of changing the shape occurs when the dirt or body undergoes decomposition (decomposition) by fungi and bacteria in the soil.

The result of the ammonification process is that ammonium will return to the soil. Not only organically, ammonification can also occur as a result of bacterial activity that converts nitrate to ammonium.

5. Denitrification


Yes, the final stage of the nitrogen cycle is denitrification. Because the cycle is always rotating, the denitrification process means reducing nitrate and then it is converted back into nitrogen gas (N2). This stage was carried out by bacteria from the genera  Bacillus,  Paracoccus, and  Pseudomonas under anaerobic conditions.

Denitrification is an important process because it removes processed nitrogen (nitrate) from the ecosystem and returns it to the atmosphere in the form of biologically inert (N2). However, this is detrimental to the plant. This is because the loss of nitrate causes plants to lack nitrogen.

Benefits of the nitrogen cycle

How do you understand or are you confused about understanding the nitrogen cycle? With these long and complicated stages, nitrogen can provide many benefits for life, you know. Here are some of them:

  • Nitrogen is a constituent of the core of amino acids, then becomes a constituent of proteins and nucleic acids. As reported by the Understanding Global Change (UGC) page of the University of California, proteins and nucleic acids are the building blocks of genetic material (RNA and DNA) that form the identity of living things.
  • Nitrogen is indispensable for the synthesis of chlorophyll. Remember, right, nitrogen is absorbed by plants? Well, the fulfillment of these nutrients causes plants to grow healthy
  • During the ammonification process, bacteria help decompose decaying animals and plants. It helps clean the environment naturally
  • Soil rich in nitrate is a favorable condition for agriculture. The nitrogen cycle helps improve soil quality. That is why fertilizers contain nitrogen compounds.

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