Soils of the - Agriculture and Agri-Food Canada

GLOSSARY
absorbed water : Water held mechanically in a soil mass and having physical properties similar to ordinar y
water at the same temperature and pressure .
acid soil : A soil material having a pH of less than 7 .0 .
adsorbed water : Water held in a soil mass by physicochemical forces and having physical propertie s
substantially different from absorbed water or chemically combined water at the same temperature an d
pressure .
aeration, soil : The process by which air in the soil is replaced by air from the atmosphere . In a well-aerate d
soil, the soil air is similar in composition to the atmosphere above the soil . Poorly aerated soils usuall y
contain a much higher percentage of carbon dioxide and a correspondingly lower percentage of oxyge n
than the atmosphere . The rate of aeration depends largely on the volume and continuity of pores in the soil .
aggregate : Sand, gravel and other similar mineral material suitable for use in construction (i .e. for road
surfaces, concrete, pavement) .
aggregate, soil : A group of soil particles cohering in such a way that they behave mechanically as a unit .
alkaline soil : Any soil that has a pH greater than 7 .0 .
alkalinity, soil : The degree or intensity of alkalinity of a soil expressed by a value greater than 7 .0 on the p H
scale .
alluvial fan : A fan-shaped deposit of alluvium laid down by a stream where it emerges from an upland into les s
steeply sloping terrain .
alluvium : Material such as clay, silt, sand, and gravel deposited by modern rivers and streams .
amorphous mineral : (i) A mineral that has no definite crystalline structure . (ii) A mineral that has a definit e
crystalline structure, but appears amorphous because of the small crystal size .
anthropogenic : Man-made, or strongly man-modified, soil materials .
apron : A relatively gentle slope at the bottom of a steeper slope, and formed of materials similar to those on th e
upper slope (i .e . alluvial fan apron).
arable soil : Soil suitable for plowing and cultivation .
aspect : A measure of the orientation of a slope by means of compass points .
Atterberg Limits (Plastic Limits) : The range of water content over which a soil exhibits plastic behaviour. Th e
Lower Atterberg Limit is the water content at which the soil is not plastic when worked and crumbles o n
application of pressure . The Upper Atterberg Limit is the water content at which the soil changes fro m
plastic to flow behaviour .
available nutrient : The portion of any element or compound in the soil that can be readily absorbed an d
assimilated by growing plants . ('Available should not be confused with "exchangeable" . )
available water : The portion of water in a soil that can be readily absorbed by plant roots ; usually considered
to be the water held in the soil against a pressure of up to approximately 15 bars .
bar : A unit of pressure equal to one million dynes per square centimeter .
base saturation percentage : The extent to which the adsorption complex of a soil is saturated wit h
exchangeable cations other than hydrogen and aluminum . It is expressed as a percentage of the tota l
cation exchange capacity .
beach deposits : Sediments that are modified in their degree of sorting, or surface relief, or both, by the actio n
of waves in forming beaches .
bearing capacity (bearing strength) : The average load per unit area that is required to rupture a supportin g
soil mass .
bedrock : The solid rock that underlies soil and the regolith or that is exposed at the surface .
blanket : A mantle of unconsolidated material thick enough to mask minor irregularities in the underlying roc k
or other deposits, but which still conforms to the general underlying topography .
bog : An area covered, or filled with, peat material which generally consists of undecomposed to moderatel y
decomposed mosses .
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