Glossary of Terms in Soil Science

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

genesis (soil )

(1) The mode of origin of the soil, especially the processes or soil-forming factors responsible for the development of the solum, the true soil, from unconsolidated parent material. (2) The division of soil science dealing with soil genesis (1).


Resulting from or produced by soil-forming processes, for example, a genetic soil profile or a genetic horizon.

genetic pan

A natural subsurface soil layer of low or very low permeability having a high concentration of small particles and differing in certain physical and chemical properties from the soil immediately above or below the pan. See also claypan and fragipan.


A group of very closely related species.

geography (soil)

Geography dealing with the areal distribution of soil types.

geological erosion

The normal or natural erosion caused by geological processes acting over long geologic periods and resulting in the wearing away of mountains, the dissection of plains, and the building up of floodplains and coastal plains. Synonymous with natural erosion.

geological erosion

See erosion (2).


An agent capable of killing germs, usually pathogenic microorganisms.


The microrelief of soils produced by expansion and contraction caused by changes in moisture. Gilgai is found in soils that contain large amounts of clay, which swells and shrinks noticeably with wetting and drying. It usually occurs as a succession of microbasins and microknolls in nearly level areas or as microvalleys and microridges parallel to the direction of the slope. See also microrelief.


Geographic Information System (GIS): a set of tools for collecting, storing, retrieving, transforming and displaying spatial referenced data. CanSIS uses a GIS called ARC/INFO.

glacial drift

All rock material carried by glacier ice and glacial meltwater or rafted by icebergs. This term includes till, stratified drift and scattered rock fragments.

glacial till

See till.

glaciofluvial deposits

Material moved by glaciers and subsequently sorted and deposited by streams flowing from the melting ice. The deposits are stratified and may occur in the form of outwash plains, deltas, kames eskers, and kame terraces. See also glacial drift and till.

gleyed soil

Soil affected by gleysation.


A soil-forming process, operating under poor drainage conditions, which results in the reduction of iron and other elements and in gray colors, and mottles. See also Gleysolic and Gleysol.


A great group of soils in the Gleysolic order. A thin (less than 8 cm, or 3 inches) Ah horizon is underlain by mottled gray or brownish gleyed material, or the soil has no Ah horizon. Up to 40 cm (16 inches) of mixed peat (bulk density 0.1 or more) or 60 cm (24 inches) of fibric moss peat (bulk density less than 0.1) may occur on the surface.


An order of soils developed under wet conditions and permanent or periodic reduction. These soils have low chromas, or prominent mottling, or both, in some horizons. See also: Gleysolic Soil Classification.


Nonhalophytic plants or plants that do not grow well when the osmotic pressure of the soil solution rises above 2 bars.

grain density

See particle density.

grain-size analysis (mechanical analysis)

See particle-size analysis.

grain-size distribution

See particle size distribution.


See structure / soil and structure types / soil.


Spheroidal soil aggregate.


Rock fragments 2 mm to 7.5 cm (3 inches) in diameter.


Containing appreciable or significant amounts of gravel. The term is used to describe soils or lands. See also coarse fragments.

gravitational potential

See water / soil.

gravitational water

Water that moves into, through or out of the soil by gravity.

Gray Brown Luvisol

A great group of soils in the Luvisolic order occurring in a moderate climate, higher than 5.5°C (42°F) mean annual temperature, and developed under deciduous and coniferous forest cover. These soils have a dark-colored mull-like surface (Ah) horizon, a light-colored eluviated (Ae) horizon, a brownish illuvial B (Bt) horizon, and a basic or calcareous C horizon. The solum is highly base saturated (NaCI extraction). This group includes soils formerly called Gray Brown Podzolic.

Gray Luvisol

A great group of soils in the Luvisolic order occurring in moderately cool climates, where the mean annual temperature is usually lower than 5.5°C (42°F). The soils have developed under deciduous and coniferous forest cover, and have an eluviated light-colored surface (Ae) horizon, a brownish illuvial B (Bt) horizon, and usually a calcareous C horizon. The solum is base saturated (NaCI extraction). The Ahe horizon, if present, is less than 5 cm (2 inches) thick. This group includes soils formerly called Gray Wooded.

great group

A category in the Canadian system of soil classification. It is a taxonomic group of soils having certain morphological features in common and a similar pedogenic environment. Examples are Black, Solonetz, Gray Brown Luvisol, Humic Podzol, Melanic Brunisol, Regosol, Gleysol, and Fibrisol.

green manure

Plant material incorporated into the soil to improve it, while the plant material is still green.

green-manure crop

A crop grown for use as green manure. See also green manure.

ground fire (Forestry)

A fire that consumes all the organic material of the forest floor and also burns into the underlying soil, for example, a peat fire. It differs from a surface fire by being invulnerable to wind. in a surface fire the flames are visible and burning is accelerated by wind whereas in a ground fire wind is not generally a serious factor.

ground moraine

An unsorted mixture of rocks boulders, sand, silt, and clay deposited by glacial ice. The predominant material is till, but some stratified drift is present. Most of the till is thought to have accumulated under the ice by lodgment, but some till has been let down from the upper surface of the ice by ablation. Ground moraine is usually in the form of undulating plains having gently sloping swells, sags, and enclosed depressions.


Water that is passing through or standing in the soil and the underlying strata. It is free to move by gravity. See also water table.


A channel caused by erosion and the concentrated but intermittent flow of water during and immediately after heavy rains. It is deep enough to interfere with and not be removed by tillage operations.

gully erosion

See erosion (2.).


A Swedish word, pronounced ""yut-tya."" A nutrient-rich sedimentary peat consisting mainly of plankton, other plant and animal residues, and mud. It is deposited in water in a finely divided condition.