What is Ammonium Nitrogen?
The ammonium ion, NH4+, is an important member of the group of nitrogen-containing compounds that act as nutrients for aquatic plants and algae. In surface water, most of the ammonia, NH3, is found in the form of ammonium ion, NH4+. This fact allows us to approximate the concentration of all of the nitrogen in the form of ammonia and ammonium combined, commonly called ammonia nitrogen, be measuring the concentration of the ammonium ions.

What factors influence the amount of ammonium nitrogen in your watershed?
1. Decaying plants and animals.
2. Animal waste
3. Industrial waste effluent
4. Agricultural runoff
5. Atmospheric nitrogen

What is the optimal amount of ammonium nitrogen concentration in a watershed?
1. Levels of ammonium nitrogen should not exceed 0.5 mg/L
2. Streams or ponds near heavily fertilized fields may have ammonium nitrogen levels that exceed 0.5 mg/L.

What factors are affected by the amount of ammonium nitrogen in a watershed?
1. Ammonium nitrogen is a compound that acts as nutrients for aquatic plants and algae. If enough nutrients are available, eutrophication and increased algal blooms may occur.
2. If ammonium nitrogen levels are too high in surface waters, they can be toxic to some aquatic organisms.
3. When ammonium nitrogen levels are high, it can increase nitrification. Consequently, dissolved oxygen concentration is lowered.
4. Low levels of Ammonium nitrogen may limit plant and algal growth.