Glossary of Terms used in Farming and Agriculture

Look here for the meanings of technical, scientific and common terms used in modern agriculture.


Aberrant.  Different from the normal type of species, genus, or higher group in one or more characters, but not readily assignable to another group

Actinomycetes.  A type of fungi that acts as an antibiotic. See Microbes.

Ad Libitum.  Feeding daily feed offerings in excess of consumption; generally, 115% of consumption

Adventitious.  Plant organs produced in an unusual or irregular position, or at an unusual time of development

Aerobic.  Capable of living only in the presence of free oxygen

Afterripening.  Enzymatic process occurring in seeds, bulbs, tubers, and fruit after harvesting; often necessary for germination or resumption of growth

Agribusiness.  A business that earns revenue from agriculture

Agricultural Biotechnology.  A range of tools, including traditional breeding techniques, that alter living organisms, or parts of organisms, to make or modify products; improve plants or animals; or develop microorganisms for specific agricultural uses. Modern biotechnology today includes the tools of genetic engineering

Agroforestry.  (1) The intentional integration of trees and shrubs into crop and animal farming systems to create environmental, economic, and social benefits  (2) Land-use system in which woody perennials are grown for wood production with agricultural crops, with or without animal production

Air Layering.  Inducing root development on an undetached aerial portion of a plant, commonly by wounding it, treating it with a rooting-stimulant, and wrapping it in moist material under a waterproof covering, so that the portion so treated is capable of independent growth after separation from the mother plant

Allelopathy.  The influence of plants, other than microorganisms, upon each other, arising from the products of their metabolism

Allergen.  A substance, usually a protein, that can cause an allergy or allergic reaction in the body

Allergy.  A reaction by the body’s immune system after exposure to a particular substance, often a protein

Alluvial.  A type of azonal soil which is highly variable and is classified by texture from fine clay and silt soils through gravel and boulder deposits

Alluvium.  Soil, usually rich in minerals, deposited by water, as in a floodplain

Amendment, Physical.  Any substance (such as sand, calcined clay, peat, or sawdust) added to soil for the purpose of altering physical conditions

Amphidiploid.  A plant possessing the sum of the somatic chromosome number of two species

Anemophilous.  Normally wind-pollinated

Animal Breeding.  Agriculture relating to the care and breeding of domestic animals such as cattle, hogs, sheep, and horses

Animal Unit.  One mature nonlactating bovine weighing 500 kg and fed at maintenance level, or, in other kinds of animals, the equivalent, expressed as (weight)0.75. Usage: The use of this term in a publication should be followed by a description in a standard format, including at least the following: kind (species and breed), class, sex, size, age, and physiological status of livestock  Abbr.: AU. Compare standard livestock unit.

Anther.  The part of the stamen that develops and contains pollen

Anthesis.  The time at which a flower comes into full bloom

Anthoxanthins.  Water-soluble pigments, widely distributed in leaves, stems, and flowers. They are mostly colorless, but can modify other colors, especially anthocyanins

Antibiosis.  Physiological antagonism of one organism toward another, used chiefly in reference to such antagonism among fungi

Antimicrobial Resistance.  Bacteria and other microorganisms that develop ways to survive drugs meant to kill or weaken them

Antioxidant.  An organic compound that accepts free radicals and thus prevents autoxidation of fats and oils. At very low concentrations in food, antioxidants not only act in retarding rancidity but protect the nutritional value or minimize the breakdown of vitamins and essential fatty acids

Apoplast.  The continuum of nonliving plant cell-wall material that surrounds the symplast. It includes the tracheary elements of xylem and the free space, and is one of two parallel pathways for solute movement through plants (the other being symplast). Substances can move through the apoplast only down a thermodynamic potential gradient

Aquaculture.  The cultivation of aquatic animals and plants, including freshwater and marine line, for food and other purposes

Arillate.  Having an aril (an appendage, outgrowth, or outer covering of a seed, growing out from the hilum or funiculus)

Aroma.  A characteristic odor, as of a plant, feed, or food

Aseptic.  Characterized by absence of contaminating fungi, bacteria, viruses, mycoplasms, and other microorganisms (e.g., in cultures)

Assimilation.  (1) The incorporation of inorganic forms of chemical elements into organic forms termed assimilates. Thus, we have the assimilation of CO2 into photosynthates such as sugar and of NO3, NH4, and SO4 into amino acids. (2) In growth analysis, net assimilation rate is given a specific definition as the rate of change of crop biomass (i.e., crop growth rate, reflecting the net of photosynthetic and respiratory activities) per unit leaf area index. Net assimilation rates can also be defined for carbon, nitrogen, or other entities. (3) The formation of protoplasm.

Auxin.  A plant hormone which causes the elongation of cells in shoots and is involved in regulating plant growth

Autotrophic.  Self-reliant Compare heterotrophic

Avoidance.  Ability of an organism to prevent an injurious stress, pathogen, or predator from penetrating its tissues (e.g., drought avoidance may be achieved through restriction of water loss or by expansion of the root system to a greater supply of water)

Axenic.  Without other living organisms. Used to refer to a pure culture, i.e., a culture uncontaminated by symbionts or parasites


Bacillus Thuringiensis (Bt).  A soil bacterium that produces toxins that are deadly to some pests. The ability to produce Bt toxins has been engineered into some crops. See Bt Crops.

Bacteria.  Microorganisms responsible for the final stage of breaking down nutrients in the root of the plant. See Microbes.

Bare Fallow.  Complete inversion and incorporation of residues for maximum decomposition, done to prevent the growth of all vegetation; usually associated with summer fallow.

Batch Drying  Drying seed in relatively small quantities held in a stationary position, as opposed to drying in a continuous moving line.

Berry.  A simple, pulpy fruit of a few or many seeds (but no stones) developed from a single ovary.

Bio-Based Industrial Product.  A commercial or industrial product (other than food or feed) that is composed of biological products or renewable domestic agricultural materials such as plant, animal, and marine materials

Bioassay(1) The use of living organisms to quantitatively estimate the amount of biologically active substances present in a sample. (2) In cell biology and molecular genetics: determination of the effectiveness of a compound by measuring its effect on plants or animal tissues or organisms in comparison with a standard preparation.

Bioeconomy.  A marketplace based on renewable biomass, bioenergy, and sustainable agricultural crops

Bioenergy.  Renewable energy produced from biomass, which is organic material such as trees, plants (including crops), and waste materials (e.g., wood waste from mills, municipal wastes, manure, landfill gas (LFG), and methane from wastewater treatment facilities)

Biofuels.  Fuels produced directly or indirectly from organic material including plant materials and animal waste.

Biological Containment.  A strategy to reduce the risks of recombinant molecules propagated within microorganisms being released into the general environment.

Biological Pest Control.  The reduction of pest populations by natural enemies, typically involving an active human role

Biologically Integrated Farming. Identification and encouragement of existing biological relationships within a farm system to reduce or avoid a farming operation’s potential negative impacts on habitats, natural resources and communities. The goal of BIFS is to use biological and cultural farming practices to reduce the use of chemicals (pesticides and fertilizers) to reduce the degradation of natural resources caused by these chemicals.

Biomass.  (1)  Biological material derived from living, or recently living organisms.  (2) The total quantity, at a given time, of living organisms of one or more species usually expressed in weight per unit area.

Biopharming.  The production of pharmaceuticals such as edible vaccines and antibodies in plants or domestic animals.

Biotechnology.  The manipulation of living organisms to be commercially used in pharmaceutical products

Biosecurity.  Practices established to protect all species against harmful biological hazards.

Bloom, Full.  The developmental stage at which essentially all florets in the inflorescence are in anthesis.

Blooming.  In the grass family: the period during which florets are open and anthers are extended. Synonym: Anthesis.

Breast height.  1.37m or 4.5ft above groundline on standing trees, a standard height in USA for recording diameter, girth, or basal area.

Brix, (Degrees).  Degree Brix (Symbol °Bx) is a measure of sugar contained in a liquid solution and is commonly used in viticulture, as well as by fresh produce, sugar, syrup and other growers to refer to the sweetness of their crop. 1°Bx is equivalent to one gram of sucrose in 100 grams of liquid solution (or one percent). The term was named for Adolf Brix, a 19th-century German mathematician and engineer.  

Bt Crops.  Crops that are genetically engineered to carry a gene from the soil bacterium Bacillus thuringiensis (Bt). The bacterium produces proteins that are toxic to some pests but non-toxic to humans and other mammals. Crops containing the Bt gene can produce this toxin, thereby providing protection for the plant. Bt corn and Bt cotton are examples of commercially available Bt crops.


Calcined Clay.  Clay minerals, such as montmorillonite and attapulgite, that have been fired at high temperatures to obtain absorbent, stable, granular particles; used as amendments in soil modification.

Calorie.  The amount of heat required to raise the temperature of 1g of H2O by 1°C. Symbol: cal.

Canopy.  The vertical projection downward of the aerial portion of plants, usually expressed as percent of ground so occupied.

Carbon Sequestration.  The process of removing carbon from the atmosphere and depositing it in a reservoir

Cellulose.  A carbohydrate formed from glucose, and a major constituent of plant cell walls; a colorless solid, insoluble in water. 

Chilling Injury.  Damage to plants at low temperatures in the absence of freezing. Chilling injury is common in plants of tropical or subtropical origin at temperatures <10°C (<50°F) or, for some fruits, <15°C (<59°F). The cause usually is a change in viscosity of lipids in membranes.

Chloroplast.  A plastid containing chlorophyll and other photosynthetic pigments within which photosynthesis takes place.

Chromosome.  The self-replicating genetic structure of cells, containing genes, which determines inheritance of traits. Chemically, each chromosome is composed of proteins and a long molecule of DNA.

Climate Change.  Long-term changes in the Earth’s climate due to extended periods of weather conditions, precipitation, and wind patterns

Clone.  A genetic replica of an organism created without sexual reproduction.

Cold-Water Insoluble Nitrogen.  A form of fertilizer nitrogen not soluble in cold water (25°C; 77°F). Abbr.: WIN.

Cold-Water Soluble Nitrogen.  A form of fertilizer nitrogen soluble in cold water (25°C; 77°F). Abbr.: WSN.

Companion Crop.  One crop sown with another, used particularly of the small grains with which forage crops are sown.

Conventional Planting.  Planting that takes place days to months after a fallow period; usually involves primary and numerous secondary tillage operations. Synonym: Delayed Planting.

Critical Level.  As applied to plant response functions, that level of a factor which is just limiting to plant performance; sometimes specifically defined as 95% of the performance when the factor is nonlimiting. Usage: Widely used in plant and soil analysis for evidence of nutrient deficiency or toxicity. With leaf-area index, used as the index sufficient for near-maximum light interception or growth rate.

Crop Residue.  Portion of plants remaining after seed harvest; refers mainly to grain crop residue, such as corn stover, or of small-grain straw and stubble.

Cross-Pollination.  Fertilization of a plant with pollen from another plant. Pollen may be transferred by wind, insects, other organisms, or humans.

Cultivar.  A contraction of cultivated variety. It refers to a plant type within a particular cultivated species that is distinguished by one or more characters

Cytokinins.  A class of hormones that promote and control growth responses of plants.


Degrees Brix. See Brix.

Dehisce.  To split open when ripe, usually along definite lines or sutures to release seeds.

Deoxyribonucleic Acid (DNA).  The chemical substance from which genes are made. DNA is a long, double-stranded helical molecule made up of nucleotides which are themselves composed of sugars, phosphates, and derivatives of the four bases adenine (A), guanine (G), cytosine (C), and thymine (T). The sequence order of the four bases in the DNA strands determines the genetic information contained.

Desert.  Land on which the vegetation is absent or sparse, is usually shrubby, and is characterized by an arid climate, hot to cool.

Developmental Stage.  Discrete portion of the life cycle of a plant, such as vegetative growth, reproduction, or senescence. Several published systems are in use for various crops to subdivide the broad stages. Usage: Preferred to growth stage (except when growth stage is part of the name of a published system). See also Bloom, Full.

Differentiation.  The process of biochemical and structural changes by which cells become specialized in form and function.

Diploid.  An organism which has two sets of chromosomes in its cells, paternal and maternal.

Dormant Seeding.  Planting seed during late fall or early winter after temperatures become too low for seed germination to occur until the following spring.

Dormant Turf.  Turfs that have temporarily ceased shoot growth due to extended drought, heat or cold stress.

Dry Weight.  Moisture-free weight.

Duff.  The partially decomposed organic matter (litter of leaves, flowers, and fruits) found beneath plants, as on a forest floor.


Ecological Niche.  Role of an organism in an ecological system.

Ecology.  The study of communities of living things and the relationships between organisms and their environment.

Ecosystem.  A system of all living things in a given area—plants, animals and organisms—which interact with each other and with non-living surrounding elements, such as weather, soil, climate, and atmosphere

Ecotone.  Transition zone between two vegetational types or vegetational regions.

Ectotrophic Mycorrhiza.  A mycorrhiza growing in a close web on the surface of an associated root; generally formed by basidiomycete fungi.

Efficiency.  Degree to which a plant or vegetation converts radiant energy into organic compounds; efficiency may depend on degree of utilization of necessary environmental components

Endotrophic Mycorrhiza.  A mycorrhiza penetrating into the associated root and ramifying between the cells; generally formed by phycomycete fungi

Enzymatic Degradation.  Chemical breakdown of a given substance by the specific enzyme catalyst for that particular chemical reaction of a biological process

Enzyme-Linked Immunosorbent Assay (ELISA).  A technique using antibodies for detecting specific proteins. Used to test for the presence of a particular genetically engineered organism

Etiolated.  Characterized (as a result of growth in the absence of light) by the development of multiple symptoms such as yellowing, elongation, thin stems, and failure of leaf expansion


Farm.  The USDA defines a farm “as any place from which $1,000 or more of agricultural products were produced and sold, or normally would have been sold, during the year.”

Feed Efficiency.  Pounds of product produced per pound of matter consumed, referred to as the feed to gain or gain to feed ratio. Beef, swine, fish, and poultry industries have used feed efficiency as a benchmark for profitability.

Fermentation.  Large-scale culture of cells suitable for recovery of cell products, including various chemical or pharmaceutical compounds, or biomass.

Fertigation.  The application of fertilizer through an irrigation system.

Fiber.  (1) A long, thick-walled cell (e.g., in cotton) serving to strengthen an organ. (2) A unit of matter characterized by a length at least 100 times its diameter or width.

Field Trial.  A test of a new technique or variety, including biotech-derived varieties, done outside the laboratory but with specific requirements on location, plot size, methodology, etc.

Flavor.  The simultaneous physiological and psychological response obtained from a substance in the mouth that includes the senses of taste (sweet, sour, salty, bitter), smell (fruity, pungent), and feel. The sense of feel as related to flavor encompasses only the effect of chemical action on the mouth membranes, such as heat from pepper, coolness from peppermint, and the like. No reliable correlation of taste with chemical structure has yet been possible. Flavor is a critical factor in the acceptability of foods, medicines, confectionery, and beverages

Flowering Stage.  The physiological stage of a grass plant in which anthesis (blooming) occurs, or flowers are visible in nongrass plants.

Flush.  Growth that is produced during a short period

Fodder.  Coarse grasses such as corn and sorghum harvested with the seed and leaves green or alive, then cured and fed in their entirety as forage


Gene.  The fundamental physical and functional unit of heredity. A gene is typically a specific segment of a chromosome and encodes a specific functional product (such as a protein or RNA molecule).

Gene Expression.  The result of the activity of a gene or genes which influence the biochemistry and physiology of an organism and may change its outward appearance.

Gene Flow.  The movement of genes from one individual or population to another genetically compatible individual or population.

Gene Mapping.  Determining the relative physical locations of genes on a chromosome. Useful for plant and animal breeding.

Gene (DNA) Sequencing.  Determining the exact sequence of nucleotide bases in a strand of DNA to better understand the behavior of a gene.

Genetic Engineering.  Manipulation of an organism’s genes by introducing, eliminating or rearranging specific genes using the methods of modern molecular biology, particularly those techniques referred to as recombinant DNA techniques.

Genetically Engineered Organism (GEO).  An organism produced through genetic engineering.

Genetic Modification.  The production of heritable improvements in plants or animals for specific uses, via either genetic engineering or other more traditional methods. Some countries other than the United States use this term to refer specifically to genetic engineering.

Genetic Yield Potential.   The yield of an ideal or optimal genotype that would capture natural resources efficiently and produce the highest yield in a target environment. Thus, estimation of ‘genetic yield potential’ is based on the possible gain in crop yield that could be achieved through genetic improvements or genotype/germplasm developments, and helps to quantify the scope of potential genetic improvements.

Genetically Modified Organism (GMO).  An organism produced through genetic modification.

Genetics.  The study of the patterns of inheritance of specific traits.

Genome.  All the genetic material in all the chromosomes of a particular organism.

Genomics.  The mapping and sequencing of genetic material in the DNA of a particular organism as well as the use of that information to better understand what genes do, how they are controlled, how they work together, and what their physical locations are on the chromosome.

Genomic Library.  A collection of biomolecules made from DNA fragments of a genome that represent the genetic information of an organism that can be propagated and then systematically screened for particular properties. The DNA may be derived from the genomic DNA of an organism or from DNA copies made from messenger RNA molecules. A computer-based collection of genetic information from these biomolecules can be a “virtual genomic library.”

Genotype.  The genetic identity of an individual. Genotype often is evident by outward characteristics, but may also be reflected in more subtle biochemical ways not visually evident.

Germination.  Resumption of active growth by the seed embryo, culminating in the development of a young plant. 

Greenhouse Gases.  Gases that contribute to the greenhouse effect by absorbing infrared radiation such as carbon dioxide and chlorofluorocarbons

Growth Analysis.  Mathematical analysis of crop or plant growth (following original concepts of Blackman and of West, Briggs, and Kidd) using relative growth rate (RGR), net assimilation rate (NAR), leaf area growth rate (LAR), and crop growth rate (CGR). Generally involves the relationship of these variables to other crop or environmental variables as integrated over time (sampling interval). See also Assimilation, Growth Rate.

Growth Rate.  A rate of change in growth (e.g., in number size or mass) of an organ, organism or community. (1) Absolute growth rate is represented by dx/dt as change in amount per unit time. (2) Specific (or relative) growth rate is dx/xdt, change per unit amount per unit time (with units of 1/time). (3) Crop growth rate is a specific plant growth analysis term denoting the absolute growth rate of mass per unit land, A, thus dw/Adt, usually in units of grams per meter per day (g m-1 d-1). Usage: Relative Growth Rate (RGR) is the usual term in plant growth analysis, whereas Specific Growth Rate (SGR) is used in most other disciplines.


Herbage.  The biomass of herbaceous plants, other than separated grain, generally above ground but including edible roots and tubers.

Herbicide-Tolerant Crops.  Crops that have been developed to survive application(s) of particular herbicides by the incorporation of certain gene(s) either through genetic engineering or traditional breeding methods. The genes allow the herbicides to be applied to the crop to provide effective weed control without damaging the crop itself.

Heirloom Crop Varieties.  Vegetation grown by gardeners and farmers in isolated or ethnic communities.

Horticulture Plants.  The cultivation of edible and non-edible plants.

Hot-Water Insoluble Nitrogen.  Fertilizer nitrogen not soluble in boiling-point hot water (100°C; 212°F); used to determine activity index of ureaforms.

Hybrid.  The offspring of any cross between two organisms of different genotypes.

Hydroseeding.  Planting seed in a water mixture by pumping through a nozzle that sprays the mixture onto a seed bed. The water mixture may also contain addends such as fertilizer and mulches.


Identity Preservation.  The segregation of one crop type from another at every stage from production and processing to distribution. This process is usually performed through audits and site visits and provides independent third-party verification of the segregation.

Immune.  Not subject to attack by a specified pest. Immunity is absolute.

In Vitro Propagation.  Propagation of plants in a controlled, artificial environment using plastic or glass vessels, aseptic techniques, and a defined growth medium.

Indigenous.  A plant native to the location where it is growing.

Inoculation.  The physical process of applying inoculant to seed or soil.

Insect-Resistance Management.  A strategy for delaying the development of pesticide resistance by maintaining a portion of the pest population in a refuge that is free from contact with the insecticide. For Bt crops this allows the insects feeding on the Bt toxin to mate with insects not exposed to the toxin produced in the plants.

Insect-Resistant Crops.  Plants with the ability to withstand, deter or repel insects and thereby prevent them from feeding on the plant. The traits (genes) determining resistance may be selected by plant breeders through cross-pollination with other varieties of this crop or through the introduction of novel genes such as Bt genes through genetic engineering.

Insecticide Resistance.  The development or selection of heritable traits (genes) in an insect population that allow individuals expressing the trait to survive in the presence of levels of an insecticide (biological or chemical control agent) that would otherwise debilitate or kill this species of insect. The presence of such resistant insects makes the insecticide less useful for managing pest populations.

Integrated Pest Management (IPM).  An ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties

Intellectual Property Rights: The legal protection for inventions, including new technologies or new organisms (such as new plant varieties). The owner of these rights can control their use and earn the rewards for their use. This encourages further innovation and creativity for the benefit of us all. Intellectual property rights protection includes various types of patents, trademarks, and copyrights.

Introduced Species.  A species not part of the original fauna or flora of the area in question, i.e., brought by human activity from another geographical region.

Irrigation, Automatic.  Hydraulic-electric control of irrigation in response to a transducer that senses plant needs. The term is commonly used more loosely to refer to hydraulic or electrically actuated valves manually present on a time-based controller.

Irrigation, Semiautomatic.  An irrigation system in which valves respond directly to a manually operated remote-control switch.


Juvenile.  A phase in the sexual cycle of a plant characterized by differences in appearance from the adult and by inability to respond to flower-inducing stimuli.


Landscape.  A collective term for all the natural features (such as fields, hills, forests, water, etc.) that distinguish one part of the earth’s surface from another part. Usually used in reference to that land or territory which the eye can comprehend in a single view, including all its natural characteristics.

Layering, Soil.  Stratification within a soil profile, which may affect conductivity and retention of water, soil aeration, and rooting; can be due to construction design, topdressing with different textured amendments, inadequate on-site mixing of soil amendments, or blowing and washing of sand or soil.

Limiting Factor.  An environmental variable (or, less often, a plant trait) found at a level that restricts the performance of the organism.

Local Population.  Group of individuals of the same species growing near enough to each other to interbreed and exchange genes.


Maturity Index.  Any mechanical, physiological, chemical, visual or other method used to determine the time of maturity for a plant species.

Meristem.  A localized group of actively dividing cells, from which permanent tissue systems (root, shoot, leaf, flower) are derived. The main categories of meristems are (i) apical meristems, in root and shoot tips; (ii) lateral meristems (vascular and cork cambiums); and (iii) intercalary meristems, in the nodal region and at the base of certain leaves. adj. meristematic.

Mesophyll.  The leaf cells that contain chloroplasts and that are located between the upper and lower epidermis.

Microbes.  Collective term for all living organisms that are too small to be seen with the naked eye. Bacteria, archaea, viruses, fungi, prions, protozoa and algae are all types of microbes. They play key roles in nutrient cycling, biodegradation/biodeterioration, food spoilage, the cause & control of disease and biotechnology. Syn. Microorganism. There are five types of microbes that live in soil:

  • Actinomycetes, a type of fungi that act as an antibiotic,
  • Bacteria, responsible for the final stage of breaking down nutrients in the root of the plant,
  • Mycorrhiza, a type of fungi living in roots which facilitate the roots’ water reuptake,
  • Nematodes, which protect the plant from different pathogens, and
  • Protozoa, which eats harmful bacteria that can harm the plant and consume its nutrients.

Microbiology.  The study of Microbes.  

Minimum Tillage(1) Minimal soil manipulation in combination with chemicals for adequate seedbed preparation and vegetation control. (2) Minimal soil manipulation in combination with chemicals and residue incorporation for minimum moisture loss, reducing energy input and labor requirement. Synonym: conservation tillage.

Molecular Biology.  The study of the structure and function of proteins and nucleic acids in biological systems.

Monoculture.  The use of one crop or family of crops either continuously, year after year, or alternated with fallow.

Multiple Crop Technologies.  The practice of growing two or more crops in the same shared space during a single growing season

Mutation.  Any heritable change in DNA structure or sequence. The identification and incorporation of useful mutations has been essential for traditional crop breeding.

Mycorrhiza.  A type of fungi living in roots which facilitate the roots’ water reuptake. See Microbes.

Mycotoxin.  A toxin or toxic substance produced by a fungus.


Nano-Catalyst.  A catalyst the size of a nanometer that causes a chemical reaction to happen more quickly

Nanometer.  A unit of spatial measurement that is 10-9 meter, or one billionth of a meter; commonly used in nanotechnology

Native Species.  A species indigenous to an area; i.e., not introduced from another environment or area.

Naturalized Plants.  Introduced species that have become established in a region. Compare native or indigenous.

Nematodes.  Microscopic worms that are mostly beneficial to plants, protecting them from different pathogens. See Microbes. For more detailed information, see The Living Soil: Nematodes, published by the USDA’s Natural Resources Conservation Service.

Nitrate Toxicity.  A variety of conditions in animals, resulting from ingestion of feed high in nitrate; the toxicity actually results when nitrate (NO3) is reduced to nitrite (NO2) in the rumen.

No-Till.  A method of planting crops that involves no seedbed preparation other than opening small areas in the soil for placing seed at the intended depth. There is generally no cultivation during crop production; instead, chemicals are used for vegetation control. Synonym: zero till.

Nucleotide.  A subunit of DNA or RNA consisting of a nitrogenous base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a phosphate molecule, and a sugar molecule (deoxyribose in DNA and ribose in RNA). Many of nucleotides are linked to form a DNA or RNA molecule.


Off-Type(1) Plants or seeds that do not conform to the characteristics of a variety as described by the breeder. (2) Plants or seeds that are not necessarily of any variety. (3) Plants or seeds resulting from (i) cross-pollination by other kinds or varieties, (ii) uncontrolled self-pollination during production of hybrid seed, or (ii) segregates from any of the above plants. See also Roguing.

Open Storage.  Storage (e.g., of seed) with free access to normal atmospheric conditions.

Organic Agriculture.  A concept and practice of agricultural production that focuses on production without the use of synthetic inputs and does not allow the use of transgenic organisms. USDA’s National Organic Program has established a set of national standards for certified organic production which are available online.

Ortet.  The original plant from which the members of a clone have descended. Compare. ramet.

Outcrossing.  Mating between different populations or individuals of the same species that are not closely related. The term “outcrossing” can be used to describe unintended pollination by an outside source of the same crop during hybrid seed production.


Pantropical.  Growing throughout the warmer regions of the world. Used especially of the ranges of widespread weeds.

Parthenocarpy.  Development of fruit without fertilization. The fruit resembles a normally produced fruit but is seedless. Varieties of the pineapple, banana, cucumber, grape, orange, grapefruit, persimmon, and breadfruit exemplify naturally occurring parthenocarpy. Seedless parthenocarpic fruit can be induced in nonparthenocarpic varieties and in naturally parthenocarpic varieties out of season by a type of artificial pollination with dead or altered pollen or by pollen from a different type of plant. The application of synthetic growth substances in paste form, by injection, or by spraying, also causes parthenocarpic development.

Pasture.  A type of grazing management unit enclosed and separated from other areas by fencing or other barriers and devoted to the production of forage for harvest primarily by grazing.

Pedigree.  (1) A system of plant breeding in which detailed records are kept of all plants in segregating generations following hybridization. (2) A record, using standardized notation, showing the line descent for a variety.

Perennial.  Persisting for several years, usually with new growth from a perennating part.

Persistent(1) Retaining its place, shape, or structure; remaining attached after the growth period; not deciduous; designating fruits, flowers, leaves, etc., that remain on a plant after frost. (2) Of a disease: difficult to control.

Pest-Resistant Crops.  Plants with the ability to withstand, deter or repel pests and thereby prevent them from damaging the plants. Plant pests may include insects, nematodes, fungi, viruses, bacteria, weeds, and other.

Pesticide Resistance.  The development or selection of heritable traits (genes) in a pest population that allow individuals expressing the trait to survive in the presence of levels of a pesticide (biological or chemical control agent) that would otherwise debilitate or kill this pest. The presence of such resistant pests makes the pesticide less useful for managing pest populations.

Phenotype.  The visible and/or measurable characteristics of an organism (how it appears outwardly).

Photosynthesis.  A process used by plants and other organisms to convert light energy from the Sun into chemical energy that can be later released to fuel the organisms’ activities

Plant Breeding.  The use of cross-pollination, selection, and certain other techniques involving crossing plants to produce varieties with particular desired characteristics (traits) that can be passed on to future plant generations.

Plant-Incorporated Protectants (PIPs).  Pesticidal substances introduced into plants by genetic engineering that are produced and used by the plant to protect it from pests. The protein toxins of Bt are often used as PIPs in the formation of Bt crops.

Plant Pests.  Organisms that may directly or indirectly cause disease, spoilage, or damage to plants, plant parts or processed plant materials. Common examples include certain insects, mites, nematodes, fungi, molds, viruses, and bacteria.

Planting Density.  The rate at which seed or vegetative propagules are placed in a field or nursery planting.

Pollination.  The transfer of pollen from the anther to the stigma of a flower.

Polymerase chain reaction (PCR).  A technique used to create a large number of copies of a target DNA sequence of interest. One use of PCR is in the detection of DNA sequences that indicate the presence of a particular genetically engineered organism.

Prebloom.  The stage or period immediately preceding blooming.

Precision Agriculture.  Technological advances meant to propel agriculture into the computerized information-based world

Preservative.  An additive used to protect against decay, discoloration, or spoilage.

Prokaryote.  A cell or organism lacking a true nucleus separated from the cytoplasm by a discrete membrane (e.g., bacteria, cyanobacteria).

Promoter.  A region of DNA that regulates the level of function of other genes.

Protected Variety.  A plant variety that is released and granted a certificate of plant variety protection under the legal statutes of the USA or some other country. The owner of a protected variety has the right during the term of the protection to exclude others from selling the variety, offering it for sale, reproducing it, importing it, exporting it, or using it in producing a hybrid or different variety.

Protein.  A molecule composed of one or more chains of amino acids in a specific order. Proteins are required for the structure, function, and regulation of the body’s cells, tissues, and organs, and each protein has a unique function.

Protozoa.  A microorganism which eats harmful bacteria that can harm a plant and consume its nutrients.  See Microbes.

Proximate Analysis.  Analytical system that includes the determination of ash, crude fiber, crude protein, ether extract, moisture (dry matter), and nitrogen-free extract.

Pseudothatch.  The upper surface layer above a thatch, made up of relatively nondecomposed leaf remnants and clippings.

Pubescence.  A general term for hairs or trichomes.


Quality Control.  The use of any device, technique, method, or person that makes possible the production, on time and at the lowest cost, of products of the quality necessary to gain full customer acceptance.

Quiescence.  The absence of growth, usually inferring the absence of environmental conditions favoring growth. Usage: Although dormant seed are quiescent, quiescence is distinguished from dormancy, which implies the inability to germinate even in the presence of environmental conditions favoring growth.


Rancidity(1) Off-flavor and aroma that occurs when foods or feeds containing oil deteriorate. It is the result of oxidation of lipids (oils) to form volatile compounds, including aldehydes and fatty acids. (2) Another form of rancidity is caused by hydrolysis of the glycerides (oils and fats) to form free fatty acids; this is the major cause of rancid butter.

Range Management.  The science of maintaining maximum range forage production without jeopardy to other resources or uses of the land.

Rangelands.  Large, open land areas containing grass, plants and shrubs used for grazing

Recombinant DNA.  A molecule of DNA formed by joining different DNA segments using recombinant DNA technology.

Recombinant DNA Technology.  Procedures used to join DNA segments in a cell-free system (e.g. in a test tube outside living cells or organisms). Under appropriate conditions, a recombinant DNA molecule can be introduced into a cell and copy itself (replicate), either as an independent entity (autonomously) or as an integral part of a cellular chromosome.

Recropping.  A system in which land is cropped annually without a fallow period (i.e., continuously cropped year after year), or in a cropping rotation longer than one year. The land may be in a cereal grain, or an alternate crop may be inserted into the rotation.

Regulation.  The degree to which a limiting factor or similar element actually controls a process.

Relative Humidity.  The ratio of the quantity of water vapor actually present in the air to the greatest amount possible at a given temperature.

Resins.  Sticky-to-brittle plant products derived from essential oils and sometimes possessing marked odors; used in medicines, varnishes, etc.

Resistant.  Able to restrict, inhibit, avoid, or tolerate the activities of a specified pest, pathogen, or environmental stress.

Ribonucleic Acid (RNA).  A chemical substance made up of nucleotides compound of sugars, phosphates, and derivatives of the four bases adenine (A), guanine (G), cytosine (C), and uracil (U). RNAs function in cells as messengers of information from DNA that are translated into protein or as molecules that have certain structural or catalytic functions in the synthesis of proteins. RNA is also the carrier of genetic information for certain viruses. RNAs may be single or double stranded.

Ripe.  Fully grown and developed; mature.

Roguing.  The act of removing or destroying off-type plants, other varieties, and objectionable weeds from a seed production field.

Row Sprigging.  Planting of sprigs in rows or furrows.


Savanna.  Grassland with scattered trees or shrubs; often a transitional type between true grassland and forestland, and accompanied by a climate with alternating wet and dry seasons.

Seed(1) A mature (ripened) ovule consisting of an embryonic plant and a store of food (stored in the endosperm, in some species), all surrounded by a protective seed coat. (2) To sow or plant seed (e.g., broadcasting or drilling of small-seeded grasses and legumes or other crops).

Seed Multiplication.  The aggregate of all practices required to grow a plant to maturity and produce seed, including those practices necessary for harvesting and preparing seeds for subsequent plantings.

Seed Vigor.  Those seed properties that determine the potential for rapid uniform emergence and development of normal seedlings under both favorable and stress conditions.

Selectable Marker.  A gene, often encoding resistance to an antibiotic or an herbicide, introduced into a group of cells to allow identification of those cells that contain the gene of interest from the cells that do not. Selectable markers are used in genetic engineering to facilitate identification of cells that have incorporated another desirable trait that is not easy to identify in individual cells.

Selective Breeding.  Making deliberate crosses or matings of organisms so the offspring will have particular desired characteristics derived from one or both parents.

Selective Medium.  Nutrient material constituted such that it will support the growth of specific organisms or genotypes while inhibiting the growth of others.

Senescence(1) The developmental stage during which deterioration occurs leading to the end of functional life of an organism or organ. Sometimes defined from specific criteria such as a decline in chlorophyll or dry weight. (2) More generally, a slowing in the rate of growth of a plant or plant organ, usually due to old age.

Shattering(1) A condition whereby seeds drop to the ground prior to harvest. (2) A method of turf cultivation involving fragmentation of a rigid or brittle soil mass, usually by a vibrating mechanical mole device.

Short-Lived Perennial.  Turfgrasses normally expected to live only 2 to 4 years.

Silage.  Forage preserved in a succulent condition by partial anaerobic, acid fermentation.

Slow-Release Fertilizer.  Fertilizer with a rate of dissolution less than is obtained for completely water-soluble fertilizers; may involve compounds that dissolve slowly, materials that must be decomposed by microbial activity, or soluble compounds coated with substances highly impermeable to water. Synonyms: controlled-availability, controlled-release, delayed-release, metered-release, and slow-acting fertilizer. Compare quick-release fertilizer.

Small Farms.  More than 90 percent of farms in the U.S. are classified as small, with a gross cash farm income of $250,000, or less

Soil Quality.  The capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation. In short, the capacity of the soil to function.

Sprig.  (1) A stolon, rhizome, tiller or combination used to establish turf. (2) To plant sprigs.

Starch Granule.  The fundamental unit in which starch is deposited in the storage tissue of many higher plants. It is paracrystalline cold-water insoluble, with a characteristic size and shape depending on the species of the plant that produced it.

Storage.  Reversible accumulation of materials in localized organelles, cells, or organs. Storage implies that the material is available for subsequent mobilization under some conditions.

Substrate(1) The substance acted on in a chemical reaction. (2) A culture medium.

Sustainable Agriculture.  An integrated system of plant and animal production practices having a site-specific application that will over the long-term satisfy human food and fiber needs

Sustained Yield.  The continuation of desired forage or animal production.


Tempered.  Brought to predetermined moisture characteristics or temperature (or both) before further processing.

Terminal.  (1) Of or relating to an end or extremity. (2) Growing at the end of a branch or stem.

Till-Plant.  Seedbed preparation and planting completed in the same operation, or one immediately following the other, leaving a protective cover of crop residue on and mixed in the surface layer. In some areas, referred to as minimum tillage.

Tolerance Range.  Range of environmental conditions in which an organism can survive; set mainly genetically, but modified by previous environmental history of the individual.

Topdressing.  A prepared soil mix added to the turf surface and worked in by brooming, matting, raking, and/or irrigating to smooth a green surface, firm a turf by working soil in decomposition, cover stolons or sprigs during vegetative decomposition, and cover stolons or sprigs during vegetative planting. Also the act of applying topdressing materials to turf.

Total Digestible Nutrients.  Sum total of the digestibility of the organic components of plant material and/or seed (e.g., crude protein + nitrogen-free extract + crude fiber + fat). Abbr.: TDN.

Toxicity(1) Being poisonous or toxic. (2) Injury, impairment, or death resulting from a poison or toxin, i.e., a toxic reaction. Synonym: toxicosis.

Traditional Breeding.   Modification of plants and animals through selective breeding. Practices used in traditional plant breeding may include aspects of biotechnology such as tissue culture and mutational breeding.

Transboundary Animal Diseases.  Highly contagious epidemic diseases that can spread extremely rapidly, irrespective of national borders. They cause high rates of death and disease in animals, thereby having serious socio-economic and sometimes public health consequences while constituting a constant threat to the livelihoods of livestock farmers

Transformation, Biochemical.  The process of using cultured cells to convert substrates into other desirable organic compounds by virtue of an endogenous enzyme system that catalyzes the reactions. Synonym. Biotransformation

Transgene:  A gene from one organism inserted into another organism by recombinant DNA techniques.

Transgenic.  Genetically modified organisms; an organism that has been generated by biotechnology

Transgenic Organism.  An organism resulting from the insertion of genetic material from another organism using recombinant DNA techniques.

Transitional Climatic Zone.  The suboptimal zone between the cool and warm climates, where both warm- and cool-season grasses can be grown.

Transpiration. The loss of water from the plant through evaporation at the leaf surface. Transpiration is the main driver of water movement in the xylem. It is caused by the evaporation of water at the leaf–atmosphere interface; it creates negative pressure (tension) equivalent to –2 MPa at the leaf surface. This value varies greatly depending on the vapor pressure deficit, which can be negligible at high relative humidity (RH) and substantial at low RH. Water from the roots is pulled up by this tension. At night, when stomata shut and transpiration stops, the water is held in the stem and leaf by the adhesion of water to the cell walls of the xylem vessels and tracheids, and the cohesion of water molecules to each other. This is called the cohesion–tension theory of sap ascent.

Trichome.  A filamentous outgrowth; specifically, an epidermal hair structure on a plant. Collectively, trichomes make up pubescence.


Variant.  Seeds or plants that (i) are distinct within the variety but occur naturally in the variety, (ii) are stable and predictable with a degree of reliability comparable to other varieties of the same kind, within recognized tolerances, when the variety is reproduced or reconstituted, and (iii) were originally a part of the variety as released. Usage: Variants are not the same as off-types.

Variety.  A subdivision of a species for taxonomic classification also referred to as a ‘cultivar.’ A variety is a group of individual plants that is uniform, stable, and distinct genetically from other groups of individuals in the same species.

Vector.  An insect or other organism that provides a means of dispersal for a disease or parasite.

Vegetative Cover.  A soil cover of plants irrespective of species.



Vegetative Stage.  The developmental stage prior to the appearance of fruiting structures. See also Whorl Stage.

Vigor.  Indicative of active growth, relative absence of disease or other stresses.


Watershed.  The area of land where all of the water that is under it or drains off of it goes into the same place

Wet Weight.  Weight before drying.


Whorl Stage.  Developmental stage of a grass plant prior to the emergence of the inflorescence. See also Vegetative Stage.

Wind Pollination.  The movement of pollen from the anther to the stigma by action of natural wind currents.


Xylem.  The portion of the conducting tissue that is specialized for the conduction of water and minerals.


Yield.  The aggregate of products resulting from the growth or cultivation of a crop and usually expressed in quantity per area. Commonly refers to the product or products consumed or marketed.

Comments and Suggestions
We are constantly working to improve our Links Library and our Glossary of Agricultural Terms, just like we're always working to improve MultiFIX.If you have any suggestions for new terms or links that you'd like to see on our site, or if you have any comments on what you found here, please let us know.
Please tell us what type of suggestion you have for us.