Mineralization

Conversion of organic N to inorganic N

Ammonification

A step in mineralization: Conversion of amino acids to ammonium

Ammonia volatilization

Conversion of ammonium ions to ammoniagas

Immobilization

Conversion of inorganic N to organic N

Nitrification

Conversion of ammonium to nitrate

Nitrosomonas

bacteria converts ammonium to nitrate

Nitrobacter

bacteria converts nitrite to nitrate

Denitrification

Conversion of nitrate to gaseous N:

N2, N20, N02

Leaching

vertical nutrient loss through the soil profile with water movement. Nitrate is the predominate N form lost via leaching since it primarily resides in the soil solution.

N fixation

Conversion of N2 gas into ammonium

Industrial N fixation

Haber-Bosch process of reacting hydrogen and nitrogen gases under temperature and pressure to create ammonium

Biological N fixation

Conversion of N2 gas into ammonium by microorganisms

Symbiotic N fixation

Conversion of N2 gas into ammonium by microorganisms in co-dependent relationship with plants. Bacteria are incorporated into root structure nodules.

Associative N fixation

Conversion of N2 gas in

Associative N fixation

Conversion of N2 gas into ammonium by microorganisms inhabiting the plant root rhizosphere

Urease

Soil and plant enzyme that hydrolyzes urea to ammonium and carbon dioxide

Inorganic N forms

chemical N forms that do not have carbon

e.g. nitrate, ammonium

Organic N forms

chemical N forms that are bonded to carbon

e.g. amino acids, proteins, DNA

Nitrate

N0₃^-

Ammonium

NH₄⁺

Nitrite

N0₂^-

Dinitrogen gas

N2

Most abundant gas in the earth's atmosphere. Reactant of N fization, product of denitrification

Nitrous Oxide

N₂0

gaseous product of dentrification. Powerful greenhouse gas that contributes to global climate change

Urea

CO(NH₂)₂

Both a natural organic molecule and a synthetic N fertilzer

Amino acids

N containing, building block monomers of protein

Nucleic acids

N containing, long, linear macromolecules, either DNA or various types of RNA, that carry genetic information directing all cellular functions

Proteins

N containing molecules that consist of amino-acid residues joined by peptide bonds

Enzymes are proteins that catalyze specific metabolic reactions

Ammonium nitrate

Solid N fertilizer that is hygroscopic and explosive. It is now commercially banned in the US because it can be used in explosives

Urea

A natural organic N molecule (excretion product in urine) as well as a popular commercially produces solid fertilizer

Anhydrous ammonia

Gaseous N; primary product of Haber-Bosch

also used as a fertilzer that can be injected directly into soil

also can be a reactant in producing other chemical fertilizers

URAN or UAN

urea ammonium nitrate

a popular liquid fertilizer

Biosolids

Sewage plant by-product (sewage sludge) that can be dried and used as a soil amendment.

Organic in nature but not certified USDA organic because of heavy metals and pathogens

Animal manure

Animal digestive waste that can be used as a soil amendment

Green manure

Crop grown specifically to accumulate plant biomass and nutrients that are then returned to the soil to promote better soil quality, reduce soil erosion and improve nutient cycling of the crop rotation

Legume

Crop capable of hosting symbiotic N fixing organisms for promoting biological N fixation

e.g. peas, beans, clover, alfalfa

Rhizobium

Symbiotic N fixing bacteria that stimulate nodule formulation on legume roots

Ammonium fixation

Physical trapping of ammonium ions between contrating 2:1 clay silicates, rendering the ammonium less plant available.

Expansion and contraction of these clays occurs during wetting/drying cycles

Methemoglobinemia

Blood disorder in which an abnormal amount of methemoglobin (a form of hemoglobin) is produced.

Hemoglobin is the molecule in red blood cells that distributes oxygen to the body.

Syndrome can occur in young infants that ingest high levels of nitrate in drinking water, resulting in oxygen starvation (blue baby syndrome)

Dead zone

Hypoxic (low-oxygen) areas in the worlds oceans/large lakes caused by excessive nutrient pollution from human activities that deplete the oxygen required to support most marine life in bottom/near bottom water

Aerobic processes

Reactions or pathways that require oxygen

e.g. organic matter mineralization, nitrification, ion uptake by plants, metal oxidation

Anaerobic processes

Reactions or pathways that do not require oxygen. These often occur under water saturated conditions

e.g. denitrification, sulfate and metal reduction