Nitrogen cycle is the biochemical cycle by which nitrogen is converted into various chemical forms as it circulates among the atmosphere , terrestial, and marine ecosystems. 

4 process are involved as shown.

1. Fixations 

2. Ammonification.

3. Nitrification.

4. Denitrification.

It describes how nitrogen moves between plants, animals, bacteria and the air and soil .

Nitrogen is important element to all life on earth.