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This picture shows how nitrogen moves between living and non-living parts of our planet.
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The Nitrogen Cycle

Nitrogen is a part of living things like plants and animals. Nitrogen is also a part of non-living things like the air above and the dirt below. Nitrogen does not stay in one place. It moves slowly between living things, dead things, the air, soil and water. These movements are called the nitrogen cycle.

On our planet, most nitrogen is in the atmosphere. About four out of five air molecules are nitrogen. All plants and animals need nitrogen to grow, but the nitrogen that is in the atmosphere is not the type that they can use. Nitrogen in the air can be changed during lightning strikes, during fires, and by special bacteria, and becomes the type that plants and animals need to grow.

Most plants get the nitrogen they need to grow from the soil or water in which they live. Animals get the nitrogen they need by eating plants or other animals that contain nitrogen. When organisms die, their bodies decay and the nitrogen in them is released into soil or into ocean water.

Last modified May 7, 2007 by Lisa Gardiner.

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