2. Background All life requires Nitrogen 79% of the air is N2 Proteins
Amino Acids
Nucleic Acid
79% of the air is N2
This form cannot be used by most organisms
Organisms need a fixed form (incorporated into a compound)

3. Usable Nitrogen Plants secure Nitrogen in a fixed form
nitrate ions (NO3−)
ammonium (NH4+)
Assimilation- Animals secure Nitrogen from plants and other animals that have eaten plants in organic material

4. Nitrogen Fixation
The breaking apart of N2 so that the atoms can combine with other atoms
3 processes:
1) atmospheric fixation
2) biological fixation
3) industrial fixation

5. Atmospheric Fixation
Energy in lighting breaks apart N2 molecule and N combines with Oxygen in the air
Nitrates (NO3-) forms in rainwater and falls to the earth
5-8% of the total nitrogen fixed

6. Biological Fixation
Some species of bacteria can fix atmospheric N2 into ammonium (NH4)
Can be free living bacteria or symbiotically associated with plants
Legumes form a symbiotic relationship with bacteria from the genus: Rhizobium

7. Industrial Fixation Haber-Bosch Process
Creates 500 million tons artificial fertilizer/year
High pressure and intense heat ( degrees F) cause atmospheric Nitrogen and Hydrogen to form Ammonia (NH3)
most of its is further processed to urea and ammonium nitrate (NH4NO3).

8. Decomposition
Proteins made by plants and animals pass through the food web
Excretions and Dead animals get broken down by decomposing microorganisms
Creates ammonia (NH3)

9. Nitrification
Ammonia from decay can be taken up directly by plants but usually converted first to nitrates (NO3-)
Bacteria break down NH3 to nitrites (NO2−) and then to nitrates (NO3-).

10. Denitrification Bacteria living deep in soils and aquatic
Reduce Nitrates to Nitrogen gas (N2) so it returns to the atmosphere
Can they keep up with the agricultural production?

11. Eutrophication
Excess Nitrates leach into ground water and get into bodies of water
Algal blooms do well with the added nutrients (sometimes toxic)
Prevent light from hitting deeper plants that produce O2, and their decomposition requires O2 use by the bacteria
Reduced O2 in the water results
Nitrates are harmful to humans and other organisms (amphibians)