The following definitions were taken mainly from Canadian Society of Soil Science (1976) supplemented by Soil Conservation Society of America (1976).


A horizon
A mineral horizon formed at or near the surface in the zone of removal of materials in solution and suspension, or maximum accu-mulation of organic carbon, or both.

A horizon that has been eluviated of clay, iron, aluminum, or organic matter, or all of these.

A horizon in which organic matter has accumulated as a result of biological activity.

A horizon markedly disturbed by cultivation or pasture.

acid soil
A soil having a pH of less than 7.0.

A group of soil particles cohering so as to behave mechanically as a unit.

alkaline soils
Any soil that has pH greater than 7.0.

Tillage; agricultural production based on cultivation practices; land that is cultivated or capable of being cultivated. Arable is used as a comparison to agriculture based on grazing (non-cultivated) systems.

B horizon
A subsoil horizon characterized by one of:
a) an enrichment in clay, iron, aluminum, or humus (Bt or Bf).
b) a prismatic or columnar structure that exhibits pronounced coatings or stainings associated with significant amounts of exchangeable sodium (Bn or Bnt).
c) an alteration by hydrolysis, reduction, or oxidation to give a change in color or structure from the horizons above or below, or both (Bin).

The solid rock underlying soils and the regolith or exposed at the surface.

A peat-covered or peat-filled wetland, generally with a high water table. The water of a bog is generally acid and low in nutrients. Bogs usually support a black spruce forest but may also be treeless. They are usually covered with sphagnum and feather mosses and ericaceous shrubs.

An order of soils whose horizons are developed sufficiently to exclude them from the Regosolic Order but lack the degrees or kinds of horizon development specified for soils in other orders. They always have Bm or Btj horizons.

bulk density, soil
The mass of dry soil per unit bulk volume.

C horizon
A mineral horizon comparatively unaffected by the pedogenic processes operative in the A and B horizons except for the process of gleying (Cg) or the accumulation of calcium carbonate (Cca) or other salts (Csa). A naturally calcareous C horizon is designated Ck.

calcareous soil
Soil containing sufficient calcium carbonate (often with magnesium carbonate) to effervesce visibly when treated with cold 0.1 N hydrochloric acid.

An assessment which focuses on the nature and degree of limitations imposed by the physical characteristics of a land unit for a certain use (Smit et al., 1984).

capability class (soil)
The class indicates the general suitability of the soils for agricultural use. It is a grouping of subclasses that have the same relative degree of limitation or hazard. The limitation or hazard becomes progressively greater from Class I to Class 7.

capability subclass (soils)
This is a grouping of soils with similar kinds of limitations and hazards. It provides information on the kind of conservation problem or limitation. The class and subclass together provide the map user with information about the degree and kind of limitation for broad land use planning and for the assessment of conservation needs.

An ion carrying a positive charge of electricity; the common sail cations are calcium, magnesium, sodium, potassium, and hydrogen.

cation exchange capacity (CEC)
A measure of the total amount of exchangeable cations that can be held by the soil; it is expressed in terms of cmols per kg of soil (formerly meq/100 g).

An order of soils that have developed under xerophytic or mesophytic grasses and forbs, or under grassland-forest transition vegetation, in cool to cold, subarid to subhumid climates. The soils have a dark-colored surface (Ah, Ahe or Ap) horizon and a B or C horizon, or both, of high base saturation. The order consists of the Brown, Dark Brown, Black and Dark Gray great groups.

The relative purity, strength, or saturation of a color; directly related to the dominance of the determining wavelength of the light and inversely related to grayness; one of the three variables of color.

classification, soil
The systematic arrangement of soils into categories and classes on the basis of their characteristics. Broad groupings are made on the basis of general characteristics and subdivisions on the basis of more detailed differences in specific properties.

As a particle-size term: a size fraction mm equivalent diameter.

A compact, coherent mass of soil produced by digging or plowing.

coarse fragments
Rock or mineral particles 2.0 mm in diameter.

coarse texture
The texture exhibited by sands, loamy sands, and sandy loams except very fine sandy loam. A soil containing large quantities of these textural classes.

consistency (i)
The resistance of a material to deformation or rupture. (ii) The degree of cohesion or adhesion of the soil mass. Terms used to describe a moist soil are - loose, very friable, friable, firm, very firm, compact, very compact, and extremely compact. Terms used to describe dry soils are loose, soft, slightly hard, hard, very hard and extremely hard.

control section
The vertical section upon which soil classification is based.

Soil drainage refers to the frequency and duration of periods when the soil is not saturated. Terms used are - excessively, well, moderately, imperfectly and poorly drained.

droughty soil
Sandy or very rapidly drained soil.

dryland farming
The practice of crop production in low-rainfall areas without irrigation.

Material that has been deposited by wind action.

The wearing away of the land surface by running water, wind, ice, or other geological agents, including such processes as gravitational creep.

The combined loss of water from a given area and during a specific period of time, by evaporation from the soil surface and by transpiration from plants.

A peat-covered or peat-filled wetland with a water table which is usually at or above the surface. The waters are mainly nutrient-rich, mmerotrophic waters from mineral soils. The vegetation consists mainly of sedges, grasses, reeds and brown mosses with some shrub cover and at times, a scanty tree layer.

fertility, soil
The status of a soil with respect to the amount and availability of elements necessary for plant growth.

An organic layer containing large amounts of weakly decomposed material whose origins are readily identifiable.

fine texture
Consisting of or containing large quantities of the fine fractions, particularly of silt and clay.

The land bordering a stream, built up of sediments from overflow of the stream and subject to inundation when the stream is at flood stage.

Material that has been transported and deposited by streams and rivers. Also alluvial.

A consistency term pertaining to the ease of crumbling of soils.

frost-free period
Season of the year between the last frost of spring and first frost of fall.

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. The great groups Gleysol, Humic Gleysol and Luvic Gleysol are included in the order.

Containing appreciable or significant amounts of gravel (particles 2 to 75 mm in diameter).

That portion of the hydrosphere which at any particular time is either passing through or standing in the soil and the underlying strata and is free to move under the influence of gravity.

growing degree days (GDD)
The accumulated heat units above a threshold temperature of 50C. They are calculated as (mean daily temperature - 5) x days.

A layer in the soil profile approximately parallel to the land surface with more or less well-defined characteristics that have been produced through the operation of soil forming processes. Soil horizons may be organic or mmeral.

One of the three variables of color. It is caused by light of certain wavelengths and changes with the wavelength.

An organic layer of highly decomposed material containing little fibre.

Abounding in rounded or conical knolls or mounds, generally of equidimensional shape and not ridge-like.

immature soil
A soil with indistinct or only slightly developed horizons.

impeded drainage
A condition which hinders the movement of water through soils under the influence of gravity.

Resistant to penetration by fluids or by roots.

indicator plants
Plants characteristic of specific sail or site conditions.

The downward entry of water into the soil.

The artificial application of water to the soil for the benefit of growing crops.

Material deposited in lake water and later exposed.

land evaluation
An assessment which involves economic and social analyses as well as physical capability. It generally involves a comparison of more than one use and is often associated with changes in land use.

All the natural features such as fields, hills, forests, water, etc., which distinguish one part of the earth’s surface from another part. Usually that portion of land or territory which the eye can comprehend in a single view, including all its natural characteristics.

A feature of a soil subgroup which indicates a bedrock contact within 50 cm of the soil surface.

See soil texture. A mixture of sand, silt and clay. It is not related to color.

A soil consistency term.

An order of soils that have eluvial (Ae) horizons, and illuvial (Bt) horizons in which silicate clay is the main accumulation product. The soils developed under forest of forest-grassland transition in a moderate to cool climate. The Gray Luvisol great group is the most common in western Canada.

medium texture
lntermediate between fine-textured and coarse-textured (soils). (It includes the following textural classes: very fine sandy loam, loam, silt loam, and silt).

An organic layer of intermediately decomposed material (between that of fibric and humic).

moderately-coarse texture
Consisting predominantly of coarse particles. (In soil textural classification, it includes all the sandy loams except the very fine sandy loam).

moderately-fine texture
Consisting predominantly of intermediate and fine sized particles. (In soil textural classification, it includes clay loam, sandy clay loam, and silty clay loam).

morphology, soil
The physical constitution, particularly the structural properties, of a soil profile as exhibited by the kinds, thickness and arrangement of the horizons and by the structure, consistence and porosity of each horizon.

Munsell color system
A color designation system that specifies the relative degree of the three simple variables of color: hue, value, and chroma. For example: IOYR 6/4 is a color with a hue 10-YR, value -6, and chroma -4. These notations can be translated into several different systems of color names as desired. See chroma, hue, and value.

neutral soil
A soil in which the surface layer, at least to normal plow depth, is neither acid nor alkaline in reaction.

An order of soils that have developed dominantly from organic deposits. The majority of organic soils are saturated for most of the year, unless artificially drained. The great groups include Fibrisol, Mesisol, Humisol and Polisol.

organic matter
The decomposition residues of biological materials derived from: (a) plant and animal materials deposited on the surface of the soils; and (b) roots and micro-organisms that decay beneath the surface of the soil.

Poorly consolidated bedrock which can be dug with a spade when moist. It is severely constraining but not impenetrable to roots. The unconsolidated and more or less chemically weathered mineral or organic matter from which the solum of a soil is developed by pedogenic processes.

parent material
The unconsolidated material and more or less chemically weathered mineral or organic matter from which the solum of a soil is developed by pedogenic processes.

particle size
The effective diameter of a particle measured by sedimentation, sieving, or micrometric methods.

Unconsolidated soil material consisting largely of organic remains (mainly derived from mosses or sedges).

Those aspects of soil science involving especially the constitution, distribution, genesis and classification of soils.

percolation, soil water
The downward movement of water through soil; especially, the downward flow of water in saturated or nearly saturated soil at hydraulic gradients of the order of 1.0 or less.

pH, soil
The negative logarithm of the hydrogen-ion activity of a soil. The degree of acidity (or alkalinity) of a soil as determined by means of glass, quinhydrone, or other suitable electrode or indicator at a specified moisture content of soil-water ratio, and expressed in terms of the pH scale.

Consisting of soil aggregates that are developed predominately along the horizontal axes, laminated; flaky.

A measure of the physical yield of a particular crop. It must be related to a specified management. Productivity may be used to describe or define suitability but it would be inappropriate as a definition of capability which puts more emphasis on vulnerability or flexibility - on available options - rather than simply yields.

profile, soil
A vertical section of the soil through all its horizons and extending into the parent material.

reaction, soils
The degree of acidity or alkalinity of soil, usually expressed as a pH value.

reconstructed soil
A soil profile formed by selected placement of suitable overburden materials on reshaped spoils.

An order of soils having no horizon development or development of the Aand B horizons insufficient to meet the requirements of the other orders. Included are Regosol and Humic Regosol great groups.

residual material
Unconsolidated and partly weathered mineral materials accumulated by disintegration of consolidated rock in place.

saline soil
A nonalkali soil containing soluble salts in such quantities that they interfere with the growth of most crop plants. The conductivity of the saturation extract is greater than 4 dS/m (formerly mmhos/cm), the exchangeable-sodium percentage is less than 15, and the pH is usually less than 8.5.

The process of accumulation of salts in soils.

A soil particle between 0.05 and 2.0 mm in diameter.

saturation percentage
The amount of water required to saturate a unit of soil (often correlated with sodicity).

A soil separate consisting of particles between 0.05 to 0.002 mm in equivalent diameter.

The unconsolidated mineral material on the immediate surface of the earth that serves as a natural medium for the growth of land plants.

A measure of the amount of sodium on the exchange complex (often expressed as sodium adsorption ratio - SAR).

soil map
A map showing the distribution of soil types or other soil mapping units in relation to the prominent physical and cultural features of the earth’s surface.

soil moisture
Water contained in the soil.

soil potential
Land evaluation at a local scale. It is determined using a process of comparing locally occurring soil landscapes on the basis of productivity and cost of managing limitations. Suitability assessments can be a useful support to the analyses in the identification and ranking of limitations.

soil structure
The combination or arrangement of primary soil particles into secondary particles, units or peds. These secondary units may be, but usually are not, arranged in the profile in such a manner as to give a distinctive characteristic pattern. The secondary units are characterized and classified on the basis of size, shape, and degree of distinctness into classes, types, and grades, respectively. Common terms for kind of structure are - single grain, amorphous, blocky, subangular blocky, granular, platy, prismatic and columnar.

soil survey
The systematic examination, description, classification, and mapping of soils in an area. Soil surveys are ranked according to the kind and intensity of field examination.

An order of soils developed mainly under grass or grass-forest vegetative cover in semiarid to subhumid climates. The soils have a stained brownish or blackish salonetzic B (Bn, Bnt) horizon and a saline C horizon. The order includes the Solonetz, Solodized Solonetz and Solod great groups.

solum (plural sola)
The upper horizons of a sail in which the parent material has been modified and within which most plant roots are confined. It consists usually of A and B horizons.

Although a common term it cannot be defined specifically. It may be the B horizon of a soil with a distinct profile. It can also be defined as the zone below the plowed soil in which roots normally grow. In this publication it refers to the soil material between 20 cm and 100 cm depth.

suitability (crop)
An estimate of the fitness of a given type of land for a specified use (FAO, 1976). It is usually local or regional in scope and management may be implicated or may have to be specified.

The relative proportions of sand, silt and clay (the soil separates). It is described in terms such as sand (5), loamy sand (LS), sandy loam (SL), loam (L), silt loam (SiL), clay loam (CL), silty clay loam (SiCL) and clay (C). See chart below.

Unstratified glacial drift deposited directly by the ice and consisting of clay, sand, gravel, and boulders intermingled in any proportion.

value, color
The relative lightness of intensity of color and approximately a function of the square root of the total amount of light. One of the three variables of color.

von Post humification scale
A manual method for estimating degree of decomposition of peat materials. It is a 10 point scale with assessment based on color of drained water and structure of hand squeezed material.

water table
The upper surface of groundwater or that level below which the soil is saturated with water.

The physical and chemical disintegration, alteration and decomposition of rocks and minerals at or near the earth’s surface by atmospheric agents.