Soils - Part 5: Nitrogen as a Nutrient Glossary


The process by which microorganisms break down complex proteins to simpler amino acids, amides, and amines.  Aminization is the first step of mineralization as part of the nitrogen cycle.

ammonia volatilization

The process by which ammonia is lost to the atmosphere.  Volatilization occurs when ammonium in the soil, because of its pH, is converted to ammonia, which dissipates as a gas.

ammonium nitrate

A dry granular material manufactured by reacting nitric acid with anhydrous ammonia. One-half of the nitrogen in ammonium nitrate is in the nitrate form, and one-half is in the ammonium form.

ammonium sulfate

A dry crystalline material (21-0-0 +24S) produced by reacting anhydrous ammonia with sulfuric acid; stores well.  An excellent choice when both nitrogen and sulfur are needed.

anhydrous ammonia

A gaseous material that is compressed and stored as a liquid. At 60oF, a gallon of anhydrous ammonia weighs 5.15 pounds. Due to the fact anhydrous ammonia needs to go through the nitrification process, it is more resistant to losses from the soil by leaching or denitrification because it is converted by bacterial action to the nitrate form more slowly than are other nitrogen sources.


Precipitation, temperature and other aspects of climate affect how specific soils are formed.


The conversion of nitrate to various gaseous forms of nitrogen which can be lost to the atmosphere (nitric oxide, nitrous oxide, dinitrogen).  Denitrification occurs under oxygen-limiting conditions, such as when soils are saturated.


An organic material in soil which is a product of plant and animal remains that have decomposed and then synthesized into something new.


The temporary tying up of inorganic nitrogen by soil microorganisms that are decomposing plant residues. Immobilized nitrogen is unavailable to plants for a time, but eventually becomes available as the decomposition of residues proceeds and populations of microorganisms decline.


The process by which organic nitrogen is converted to nitrate through bacterial activity, and as influenced by temperature and precipitation.


Element needed in large amounts for plant development; found naturally and in applied fertilizers.

nitrogen cycle

The transitional process taking nitrogen from its simplest stable form (dinitrogen) and following it through fixation, mineralization, nitrification, leaching, plant assimilation, ammonia volatilization, denitrification and immobilization.

nitrogen fixation

The process of converting dinitrogen gas to chemically reactive forms, where nitrogen combines with other elements, such as oxygen, hydrogen and carbon.


The measurement of an aqueous solution’s acidity and alkalinity; measured on a scale of 1 to 14. Pure water has a pH of 7.0 and is neutral. Different crops grow best at different pH levels; pH influences herbicide activity and nutrient uptake.


The top layer of the Earth’s surface, consisting of four major components: air, water, organic matter and mineral matter. There are three categories of soil particles--sand, silt and clay--which are called "soil separates."

soil development

Five factors influence the development of a specific soil:  parent material, climate, living organisms, topography and time.

soil texture

Determined by the proportion of different soil separates--sand, silt and loam--in a soil.


A dry nitrogen material produced by reacting ammonia with carbon dioxide.  Urea contains the highest percentage of nitrogen of the commonly used dry fertilizers and is rapidly replacing ammonium nitrate. When surface applied, urea is the most rapidly volatilized of the dry nitrogen materials.