1. The Nitrogen Cycle

2. Why is Nitrogen Important? • Nitrogen is important to both plants and animals. Nitrogen is used in making proteins, DNA, and chlorophyll.

3. How does nitrogen become part of living organisms? • The atmosphere is made up of approximately 78% nitrogen. This atmospheric nitrogen (N2) is not in a form that can be used by plants and animals. • Nitrogen Fixation or Nitrification: is the process where atmospheric nitrogen is converted into a useable form of nitrogen.

4. Nitrogen Fixation • Nitrogen fixation by lightning accounts for only 1% of fixation. The energy from lightning causes nitrogen in the air to combine with oxygen forming nitrates (NO3) • Nitrogen fixation by bacteria . Some bacteria (nitrogen-fixing bacteria) convert atmospheric nitrogen (N2) into ammonium(NH4+). Some decomposing bacteria will break down plant and animal wastes to release ammonium as well. • Nitrifying bacteria convert ammonium into a usable form for plants. These bacteria convert ammonium(NH4) into nitrates (NO3).

6. Denitrification • Denitrifying bacteria convert nitrates (NO3) back into atmospheric nitrogen (N2). • This completes the nitrogen cycle

8. Human Impacts on Nitrogen Cycle • The use of nitrogen-rich fertilizers can cause nitrogen to leach into nearby waterways. The increased nitrate levels cause plants to grow rapidly until they use up the nitrate supply and then die. The number of herbivores will increase when the plant supply increases and then the herbivores are left without a food source when the plants die. This can affect the entire food chain.

9. Human Impacts of Nitrogen Cycle • Farming also affects the nitrogen cycle. The waste from livestock farming releases a large amount of nitrogen into soil and water. In the same way, sewage waste adds nitrogen to soils and water.