Denitrification is a crucial step in the nitrogen cycle.

During this process, nitrates are converted to another form.  Originally, the nitrates are found in soil or in dead organic matter.

During the denitrification process, the nitrates become nitrite, nitrous oxide, ammonia, or elemental nitrogen.  Most commonly, the nitrates are converted into the pure nitrogen element.

A form of bacteria called denitrifying bacteria enable the denitrification process to convert the nitrates.  The reaction is known as a reduction reaction in chemistry.  No oxygen is used in the process.

This process takes place frequently in nature.  When flooding occurs, the water covers the soil and denies it access to the oxygen in the air above.  As a result, the soil can undergo denitrification.

Denitrification happens naturally in the environment.  When organisms die, they must decay through this process.

However, denitrification can also be a harmful and undesirable consequence of flooding.  It can remove fertilizers from the soil, making growing plants or crops more difficult.  As a result, building dams or clear-cutting forests often has problematic results.