Skip to content Skip to sidebar Skip to footer

6 Important Processes Role of the Nitrogen Cycle (Complete+Pictures)

Nitrogen Cycle

Nitrogen Cycle Nitrogen is a chemical element that is so important for living things. The element nitrogen is always present in every living thing’s body. Amino acid as a chemical constituent of life is also composed of the chemical element nitrogen.

About Nitrogen

In 1772 a Scottish physician Daniel Rutherford discovered nitrogen.

Nitrogen is the fifth most abundant element in the universe and makes up about 78% of Earth’s atmosphere, which contains about 4,000 trillion tons of gas.

Nitrogen is obtained from liquid air through a process known as fractional distillation. Nitrogen can also undergo changes into various other forms called the nitrogen cycle.

Nitrogen is an element that can be easily accessed by humans. Nitrogen is in the form of an N2 compound with a volume content of 78.03% by volume and 75.45% by weight.

Read also : Bacteria Structure

Nitrogen is a colorless, odorless and tasteless gas that liquefies at –195.8 degrees Celsius and freezes at –210 degrees Celsius.

Important Processes Role of the Nitrogen Cycle

The nitrogen cycle is a process of converting or changing compounds containing nitrogen elements into various other chemical forms.

Nitrogen Cycle
Nitrogen Cycle

These changes can occur biologically or non-biologically. Some important processes in the nitrogen cycle or cycle include:

1. Fixation

Nitrogen fixation is basically a process of combining atmospheric nitrogen with other elements to form useful compounds.

There are only a few ways in which nitrogen, which is relatively difficult to react with other elements, can actually be combined with other elements.

Nitrogen has an important role for living things and because most organisms cannot use nitrogen if it is not combined with other elements, nitrogen fixation is an important process for the survival of life on earth.

Improvements or incorporation in the nitrogen cycle is also required for the manufacture of various substances including explosives and commercial fertilizers.

Read also : Moss Horn

Nitrogen is fixed by some microorganisms and lightning. This natural fixation has an important role in the nitrogen cycle.


Humans learned to fix large amounts of nitrogen to increase the amount of nitrogen naturally since the 20th century. Synthetic nitrogen fixation processes include the electric arc process, the cyanamide process and the Haber process.

The reaction for biological nitrogen fixation can be written as follows: N2 + 8 H+ + 8 e− → 2 NH3 + H2

2. Mineralization

Mineralization is decomposition, which is the process of oxidation of chemical compounds in organic matter where the nutrients in these compounds are released in dissolved inorganic forms that may be available to plants.

Mineralization is the opposite of immobilization, namely the inability to move actively.

Mineralization increases the bioavailability of nutrients available in decomposed organic compounds mainly due to their quantity, elements nitrogen, phosphorus and sulfur.

3. Nitrification

Nitrification is the process of forming nitrate compounds from ammonium compounds.

An important process in the nitrogen cycle is the process in which ammonium ions are oxidized to nitrite ions, then nitrite ions to nitrate ions. This process can occur in soil, seawater or fresh water.

Nitrification will be available naturally in an environment in which there is the presence of bacteria specifically for the nitrification process. The rate of the nitrification reaction is highly dependent on various environmental factors.

Read also : Difference between DNA and RNA

Some of these factors include the substrate and oxygen concentration, temperature, pH and the presence of toxic substances or substances that inhibit the nitrification process.

Sudden changes in temperature are not able to affect the speed of bacterial growth itself so it does not affect the reaction speed of the nitrification process.

The appropriate temperature in this nitrification process is from 0 to 20 degrees Celsius because at that temperature, nitrifying bacteria experience maximum growth so that it affects the speed of the nitrification process.

In addition, the oxygen concentration also affects the speed of the nitrification process. This is related to nitrifying bacteria that require oxygen.

The pH content of the environment also affects the speed of the nitrification reaction. This nitrification reaction occurs most rapidly at pH 8 to 9.

These factors are related to the survival of nitrifying bacteria.

The nitrification process can be written with the following reaction:

  • NH3 + CO2 + 1.5 O2 + Nitrosomonas → NO2- + H2O + H+
  • NO2- + CO2 + 0.5 O2 + Nitrobacter → NO3-
  • NH3 + O2 → NO2− + 3H+ + 2e−
  • NO2− + H2O → NO3− + 2H+ + 2e

4. Denitrification

Denitrification is the process of reducing nitrate to nitrogen gas. Nitrate or NO3- which is used as an alternative electron acceptor in anaerobic respiration is reduced to nitrogen gases such as N2, NO or N2O.

On the other hand, denitrification is a detrimental process. For example, in agricultural land that is given nitrate fertilizer if it is inundated by water, anoxygenic conditions will occur and denitrification can occur so that it will release nitrogen into the air.

The production of N and N20 gases carried out in the denitrification process can have consequences on the environment.

N2O can be oxidized to NO in the atmosphere. NO can react with ozone to form NO2- and return to earth to form nitric acid or HNO2.

Denitrification has a role in the destruction of ozone so that ultraviolet rays can enter the earth and cause acid rain.

Acid rain will automatically make the soil acidic and acidic soil will change the soil structure and microbial community.

Read also : Mosquito Life Cycle

The denitrification process is required for wastewater treatment. By releasing nitrate as volatile nitrogen, denitrification can minimize nitrogen fixation so that algae growth when wastewater treatment will be released into lakes or rivers.

Denitrification generally proceeds through some combination of the following intermediate forms:

  • NO3− → NO2− → NO + N2O → N2 (g)

The complete denitrification process can be expressed as a redox reaction:

  • 2 NO3− + 10 e− + 12 H+ → N2 + 6 H2O

5. Assimilation

Assimilation in the nitrogen cycle is the formation of organic nitrogen compounds such as amino acids from inorganic nitrogen compounds present in the environment.

After the nitrification process altered by bacteria, plants absorb nitrogen in the form of nitrate. Nitrates are absorbed into plants by the proton transporter nitrate gradient.

Nitrates are transported from roots to shoots via xylem. Reduction of nitrogen is carried out in the shoots. Nitrates are reduced to nitrites by nitrate reductase in the cytosol. Then the nitrite is reduced to ammonia in the chloroplast by ferredoxin-dependent nitrite reductase.

6. Ammonification

Ammonification is the stage in the nitrogen cycle in which plant residues and waste products are broken down by microorganisms to produce ammonia.

Microorganisms in the soil feed on dead organic matter into energy and they produce ammonia and other basic compounds which are the by-products of their metabolism. This ammonia is retained in the soil in the form of ammonium ions.

The Role of the Nitrogen Cycle or Cycle

Nitrogen cycle process

The nitrogen cycle is so important because nitrogen is one of the most important nutrients for plant growth.

Nitrogen in various forms always goes through natural cycles and agricultural ecosystems.

The nitrogen content and supply to the soil and the loss of nitrogen from the soil determine crop production and sustainability.

Read also : Ingenhousz . Experiment

In plants, nitrogen is one of the main elements needed for plant growth and reproduction.

Chlorophyll is nitrogen whose presence is very important for the process of photosynthesis. Nitrogen is required for rapid plant growth.

Bacteria Supporting the Nitrogen Cycle Process

In the nitrogen cycle process, of course, certain types of bacteria are needed to support the process.

Here are some of the bacteria used in the nitrogen cycle:


Rhizobium bacteria is one of the bacteria that can bind nitrogen. Usually these bacteria are found in the fixation process because bacteria that are free in the air will be bound by these bacteria.

Rhizobium bacteria are able to fix nitrogen and convert nitrogen into nitrate.

Micrococcus Denitrifican

Micrococcys denitrifican bacteria is one of the bacteria in the ammonification process. Ammonification is one of the nitrogen cycle processes.

Actually this ammonification process can be detrimental to many plants because it binds to nitrates in the soil. This binding is carried out by bacteria and then converted into ammonium.


Nitrobacter is one of the bacteria that is in the process of the nitrogen cycle, namely the nitrification process. In the nitrification process, Nitrobacter bacteria function as a supporter in the process of converting nitrite to nitrate.

Read also : Animal-like Protists

The nitrogen cycle turns out to be much needed in nature to collaborate with other elements and convert the compounds they contain into functions for various other processes that can be useful for humans, plants and so on.