Nitrogen in the environment goes through a complex cycle of chemical and biological changes. Nitrogen can take many forms including nitrate-nitrogen, ammonium nitrogen, and organic nitrogen. All nitrogen sources can turn into nitrate, which is the most mobile form. Nitrate occurs naturally in the soil. A diagram of the nitrogen cycle is located below.
Nitrate in the soil is highly water-soluble and can leach into groundwater under natural and altered conditions. This poses economic and environmental concerns. Nitrate losses occur after fires, land clearing or disturbances, and the conversion to farming operations. It is expected that some nitrogen will be lost under cropland. In Minnesota, a majority of the nitrogen contributions come from soil organic matter, fertilizer, manure and legume crops. Therefore it is important that nitrogen from these sources be managed properly to minimize environmental impacts.
![Graphic illustration of the nitrogen cycle on a farm field with corn and soybean crops. Atmospheric nitrogen is converted to ammonium and organic nitrogen respectively through atmospheric fixation and deposition and biological fixation by legumes and is added to the soil. Animal manures and biosolids, plant residues, and commercial fertilizers (industrial fixation) are sources of nitrogen that are incorporated into the soil as organic nitrogen (manure, biosolids, plants), ammonium (manure, biosolids, commercial fertilizers), or nitrate (commercial fertilizer). Once in the soil, organic nitrogen can be converted to ammonium, and ammonium to organic nitrogen or nitrate. Ammonium can be adsorbed, fixed, volatilized, or be taken up by plants. Nitrate can leach deeper into the soil, be taken up by plants or released back into the air through denitrification. Nitrogen leaves the system through crop harvest or by runoff and erosion.](/sites/default/files/inline-images/nitrogencycle.jpg)
Additional programs and resources to assist with Nitrogen Management
Nitrogen Fertilizer Best Management Practices
Nutrient Management Initiative
Irrigation Water Quality Protection - Irrigation Specialist