Why do we need nitrogen?  What are the sources of nitrogen?

Nitrogen is essential for all living things: animals and plants. Nitrogen forms a part of the proteins and DNA that are found in cells. Animals get nitrogen by eating plants and other animals.  

Just like animals, plants require nitrogen to grow and survive.  But they do not get nitrogen by consuming proteins like animals do.  Plants get nitrogen from water and from the soil. They get nitrogen by absorbing it in the form of nitrates and ammonium.  Nitrates are the major source of nitrogen for aquatic plants. 

Nitrates are not utilized by aquatic organisms such as fish and aquatic insects, but nitrates are used by plants.  

Notice that this is a cycle that recirculates nitrogen between air and soil.  For more on the nitrogen cycle and other cycles, click here.

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