Q. What is the nitrogen cycle?

The nitrogen cycle represents the recycling and circulation of the chemical element nitrogen in nature. The nitrogen cycle fundamentally depends on the action of various specialized bacteria. The Bacteria of the soil called as nitrogen-fixing bacteria present in plant roots absorb molecular nitrogen from the air and liberate nitrogen in the form of ammonia. The decomposition of organic material as well produces ammonia. In the roots and soil (mainly of leguminous plants), a first group of chemosynthetic bacteria called nitrifying bacteria, the nitrosomonas, produces energy consuming ammonia and releasing nitrite (NO2). The second group of the nitrobacteria, nitrifying bacteria, uses nitrite in chemosynthesis releasing nitrate (NO3). In the form of nitrate, the nitrogen is then incorporated by plants to be used as constituent of nucleic acids and proteins and the element then follows along the food chain. The Nitrogen returns to the atmosphere by the action of denitrifying bacteria that use nitrogen-containing compounds from the soil and release nitrogen gas (molecular nitrogen).