Nitrogen Cycle

That's a very broad question. You could find looking it up in a biology textbook helpful.

Alternatively, check out these web pages.

The Nitrogen Cycle

The Nitrogen Cycle

CHEMISTRY AND ISSUES IN THE ENVIRONMENT -The Nitrogen Cycle





There's plenty of pages on the web with descriptions and diagrams.

Here's a science experiment that illustrates the principles of the Nitrate Cycle. Take a 10 gallon aquarium filled with clean water and 20 guppies. Then add 1 lb. of hamburger meat. Then wait a week.