what is nitrogen cycle and processes involved in it??

decribe the processes also.

Nitrogen cycle consists of four main steps namely:

1. Nitrogen Fixation
2. Ammonification/ Decay
3. Nitrification
4. De-nitrification

It is important to note that microorganisms play an important role in each of these steps.

What is the mechanism of each of these steps?

Nitrogen Fixation

This is the first step of the nitrogen cycle. This step is characterized by the conversion of atmospheric N2 into ammonia (NH3). Bacteria like Azotobacter and Rhizobium have a major role in this process. They are harbored in the roots of the leguminous plants and help convert inert nitrogen to ammonia. Nitrogen fixation can occur in any of the following ways: atmospheric fixation (involves lightening), industrial fixation(manufacturing ammonia under high temperature and pressure condition)

Assimilation

Once the nitrogen has been fixed in the soil, plants can absorb nitrogen through their roots. This process of absorption is known as assimilation.

Ammonification

This is another process by which ammonia can be generated. Organic remains of plants and animals are broken down in the soil by some bacteria to release ammonia into the soil. These dead and waste matter is used by these microorganisms as food and they release ammonia into the soil.

Nitrification

This occurs in two-steps. The first step is in which NH3/NH$+ is converted to NO3- (nitrates). The bacteria Nitrosomonas and Nitrococcus present in the soil convert NH3 to NO2-, and another bacterium, Nitrobacter converts NO2- to NO3-. These bacteria gain energy through these conversions.

Denitrification

Is the reverse of nitrification that occurs in the deep layers of soil where the bacteria convert NO3- is converted into N2 and other gaseous compond like . This occurs because in deep layers of soil, oxygen is not available and the soil bacteria use these nitrogen compounds instead of oxygen.