Solution Center for Nutrient Management
Solution Center for Nutrient Management
Solution Center for Nutrient Management
University of California
Solution Center for Nutrient Management

Glossary of Nutrient Management Terms

Agricultural nutrient management can employ many complicated terms.  Our growing glossary will provide background information on frequently used terminology. There are also many other useful glossaries on nutrient management and climate change related themes listed in our references section.




Non-living. Abiotic resources comprise non-living things, for instance land, water, air and minerals.


The process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate harm or exploit beneficial opportunities. In natural systems, human intervention may facilitate adjustment to expected climate and its effects.2

Adaptive capacity

The ability of systems, institutions, humans, and other organisms to adjust to potential damage, to take advantage of opportunities, or to respond to consequences.


Requiring oxygen.

Ammonium (NH4+)

This form of nitrogen can be used by plants, or converted to nitrate by bacteria (and then taken up by plants). It is a positively charged ion (cation), attracted to negatively charged soil clay. For this reason, it is not leached to a great extent.


See mineralization.

Ammonia volatilization

The conversion of ammonium nitrogen to ammonia gas by soil microorganisms.  This usually occurs in soils with a high pH, that is a pH greater than 7.5, which are not common in California


The absence of oxygen.


Effects which relate specifically to human activities.




The variability among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are part. It includes diversity within species (genetic diversity), between species (species diversity), and between ecosystems (ecosystem diversity).

Biological nitrogen fixation

A process where symbiotic (mutually beneficial) and nonsymbiotic organisms can incorporate atmospheric dinitrogen (N2) gas into organic N forms


The total weight of all the biological material or the combined mass of all the animals and plants inhabiting a defined area; usually expressed as dry weight per area.



Carbon cycle

The term used to describe the flow of carbon (in various forms, e.g., as carbon dioxide) through the atmosphere,
ocean, terrestrial and marine biosphere, and lithosphere.

Carbon dioxide (CO2)

A naturally occurring gas, also a by-product of burning fossil fuels from fossil carbon deposits, such as oil, gas, and coal, of burning biomass, of land use changes, and of industrial processes (e.g., cement production). It is the principal anthropogenic greenhouse gas that affects the Earth’s radiative balance. It is the reference gas against which other greenhouse gases are measured and therefore has a Global Warming Potential of 1

Carbon dioxide equivalent

A metric measure used to compare the emissions from various greenhouse gases based upon their global warming potential (GWP).

Carbon footprint

The total amount of greenhouse gases (carbon dioxide) that are emitted into the atmosphere each year by a person, family, building, organization, company, or other entity.

Carbon sequestration

The capture and removal of carbon dioxide from the atmosphere and storing it in an alternative carbon related reservoir, e.g. soil organic matter, charcoal, tree growth.

Cation Exchange Capacity

The measure of a soil's ability to retain positively-charged ions (cations); this measure is usually related to a soil's overall level of fertility

Schematic of Cation Exchange




An anaerobic process where nitrate (NO3-)is converted by  into nitrogen gas (N2) specialized bacteria.  The conversion of nitrate to dinitrogen is often incomplete and results in the production of nitrous oxide, a potent greenhouse gas.  Denitrificiation occurs in the soil only in low oxygen environments, often associated with flooding or soils nearly saturated with water. 



A dynamic complex of plant, animal and microorganism communities and their non-living environment interacting as a functional unit.

Ecosystem process

An intrinsic ecosystem characteristic whereby an ecosystem maintaings its integrity.  Ecosystem processes include decomposition, production, nutrient cycling, and fluxes of nutrients and energy.

Ecosystem service

Ecological processes or functions having monetary or non-monetary value to individuals or society at large.

Emission factor

The average emission rate of a given greenhouse gas (GHG) for a given source, relative to units of activity


The enrichment of the nutrient load in ecosystems (terrestrial and aquatic), especially compounds of nitrogen and/or phosphorous.  This leads to an undesirable disturbance to the balance of organisms in the ecosystem, affecting terrestrial and aquatic biodiversity and water quality.



See transpiration.


Field Capacity

A measure of a soil's ability to hold water against downward movement due to gravity. This water content is usually reached 2-3 days after a soil has been irrigated or experienced a significant rain event.



Global Warming Potential

A measure of the total energy that a gas absorbs over a particular period of time (usually 100 years), compared to carbon dioxide

Greenhouse gas (GHG)

Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of terrestrial radiation emitted by the Earth’s surface, the atmosphere itself, and clouds. This property causes the greenhouse effect. Water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and ozone (O3) are the primary greenhouse gases in the Earth’s atmosphere. Moreover, there are a number of entirely human-made greenhouse gases in the atmosphere, such as the halocarbons and other chlorine- and bromine-containing substances, dealt with under the Montreal Protocol. Beside CO2, N2O, and CH4, the Kyoto Protocol deals with the greenhouse gases sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs),
and perfluorocarbons (PFCs).

Haber-Bosch process

The high pressure chemical process which synthesizes reactive nitrogen as ammonia (NH3) from reaction of N2 and H2.  Fritz Haber was responsible for the discovery of the process (1908) and Carl Bosch later developed the technique on an industrial scale



The incorporation of compounds (such as reactive nitrogen) into soil microbial biomass, rendering it unavailable for plant uptake.

Irrigation well

Refers to unregulated wells used for irrigation and other agricultural purposes, but not for drinking water.




The washing out of soluble ions and compounds by water draining through soil



During decomposition of plant or animal material, specialized bacteria transform nitrogen to ammonia (NH3) or ammonium (NH4+); the latter can be taken up by plants

Mitigation (of climate change)

A human intervention to reduce the sources or enhance the sinks of greenhouse gases.



Nitrate (NO3-)

A naturally occurring, negatively charged ion that is the primary form of nitrogen used by plants.

Nitrite (NO2-)

A naturally occurring, negatively charged ion.  Nitrite can be produced by the oxidation of Ammonium (NH4+), which is the first step in the nitrification process.  Accumulation of nitrite is usually rare in agricultural soils.


An aerobic process where  ammonium (NH4+) is converted to nitrite (NO2-) and nitrite to nitrate (NO3-) by specific types of bacteria.  Nitrous oxide, a potent greenhouse gas, can be produces as an intermediary biproduct during this process.

Nitrification inhibitor

A compound which decreases the activity of the microbes responsible for nitrification, delaying the conversion from the relatively-immobile ammonium (NH4+) to the easily-leached nitrate (NO3-). There are several compounds that can inhibit nitrification, but they are generally either fertilizer coatings or mixed in with fluid fertilizer formulations.

Nitrogen cycle

The circulation of nitrogen among the atmosphere, plants, animals, and microorganisms that live in soil and water.

Nitrogen fertilizer recovery efficiency

The percentage of fertilizer-N recovered in aboveground plant biomass during the growing season.

Nitrogen gas (N2), also dinitrogen gas

Dinitrogen gas occurs when two nitrogen atoms form a very strong, trivalent chemical bond; it comprises 78% of the atmosphere. Although largely inert, nitrogen gas can be "fixed" into biologically useful forms in the soil

Nitrogen, organic

“Organic nitrogen” refers to a nitrogen compound that had its origin in living material and is still part of a carbon-chain complex. It can enter soil as decomposed plant or animal tissue. It is not available to plants until microorganisms transform it to ammonium (NH4+).

Nitrogen use efficiency (NUE)

The proportion of all N inputs that are removed in harvested crop biomass, contained in recycled crop residues, and incorporated into soil organic matter and inorganic N pools.

Nitrous oxide (N2O)

An oxide of nitrogen formed mainly as a biproduct of microbial processes (see denitrification and nitrification) in soil and water.  It is also emitted by combustion and other industrial processes. N20 is a potent greenhouse gas that is 298 times more effective at trapping heat in the atmosphere than carbon dioxide over a 100 year period



Organic  amendment

Any material of biological origin.

Organic nitrogen

See Nitrogen, organic.



 Partial factor productivity for N fertilizer

The amount of increase in yield of the harvested portion of a crop per unit of fertilizer N applied.


Reactive nitrogen

Collectively any chemical form of nitrogen other than di-nitrogen


Interface between land and a river or stream

Riparian Habitat
Riparian Habitat


Mammals with a four-chamber complex stomach, that digests plant-based food by initially softenting it within the animal's first stomach, then regurgitating the semi-digested mass, now known as cud, and chewing it again.  The process of rechewing the cud to further break down plant matter and stimulated digestion is called 'ruminating'




Any crop that is harvested green and preserved in a succulent condition by partial fermentation, often preseved in a silo.


Any process, activity or mechanism that removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere.

Specialty crop

Fruits, vegetables, tree nuts, dried fruits, and horticulture and nursery crops (including floriculture)

Synthetic fertilizer

A "human made" commercially prepared inorganic compound of plant nutrients.




The process by which water is drawn through plants and returned to the air as water vapor.  Evapotranspiration is combined loss of water to the atmosphere via the processes of evaporation and transpiration


The conversion of a liquid or a solid into a gas



Water-use efficiency (WUE)

Carbon gain by photosynthesis per unit of water lost by evapotranspiration. It can be expressed on a short-term basis as the ratio of photosynthetic carbon gain per unit transpirational water loss, or on a seasonal basis as the ratio of net primary production or agricultural yield to the amount of water used.


 (top of page)


1FAO Glossary on Organic Agriculture

2IPCC WGII AR5 Glossary

3Rosenstock, T. S., Liptzin, D., Six, J., & Tomich, T. P. (2013). Nitrogen fertilizer use in       California: Assessing the data, trends and a way forward. California Agriculture, 67(1),       68–79.

4European Nitrogen Assessment glossary

5European Commission Agriculture and Rural Development Glossary

6USDA/NRCS Fate and Transport of Nutrients: Nitrogen 

7EPA Glossary of Climate Change Terms

8United Nations Framework Convention on Climate Change

9Paul, E. A. (2014). Soil microbiology, ecology and biochemistry. Academic press.

10Cassman, K. G., Dobermann, A., & Walters, D. T. (2002). Agroecosystems, nitrogen-use efficiency, and nitrogen management. AMBIO: A Journal of the Human Environment31(2), 132-140. (link)

11National Agricultural Library Agricultural Glossary (USDA)

12California Department of Food and Agriculture (CDFA) Specialty Crop Block Grant Program 


Webmaster Email:,