What is the nitrogen cycle?

The nitrogen cycle represents the circulation and recycling of the chemical element nitrogen in nature.

The nitrogen cycle basically depends on the action of some specialized bacteria. Bacteria of the soil called nitrogen-fixing bacteria there in plant roots absorb molecular nitrogen from the air and liberate nitrogen in the produce of ammonia. The decomposition of organic material also creates ammonia. In the soil and roots (mostly 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 nitrifying bacteria, the nitrobacteria, uses nitrite in chemosynthesis releasing nitrate (NO3). In the type of nitrate, nitrogen is then incorporated by plants to be used as constituent of proteins and nucleic acids and the element then follows with the food chain. 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).