Soils of the - Agriculture and Agri-Food Canada

hue : The aspect of colour that is determined by the wavelengths of light, and changes with the wavelength .
Munsell hue notations indicate the visual relationship of a colour to red, yellow, green, blue, or purple, or a n
intermediate of these hues . See also Munsell colour system, chroma ; and value, colour .
humic layer : A layer of highly decomposed organic soil material containing little fiber .
humus : (i) The fraction of the soil organic matter that remains after most of the added plant and anima l
residues have decomposed . It is usually dark coloured. (ii) Humus is also used in a broader sense t o
designate the humus forms referred to as forest humus . They include principally mor, moder, and mull . (iii )
All the dead organic material on and in the soil that undergoes continuous breakdown, change, an d
synthesis .
igneous rock : Rock formed by the cooling and solidification of magma . It has not been changed appreciably
since its formation .
illuvial horizon : A soil horizon in which material carried from an overlying layer has been precipitated fro m
solution or deposited from suspension as a layer of accumulation .
illuviation : The process of depositing soil material removed from one horizon in the soil to another, usually from
an upper to a lower horizon in the soil profile . Illuviated substances include silicate clay, hydrous oxides of
iron and aluminum, and organic matter .
impeded drainage : A condition that hinders the movement of water by gravity through soils .
impervious : Resistant to penetration by fluids or roots .
indurated layer : A soil layer that has become hardened, generally by cementation of soil particles .
infiltration : The downward entry of water into the soil .
infiltration rate : A soil characteristic determining or describing the maximum rate at which water can enter th e
soil under specified conditions, including the presence of excess water .
inorganic soil : A soil made up mainly of mineral particles ; a soil containing less than 17% organic carbon .
irrigation : The artificial application of water to the soil for the benefit of growing crops .
kame : An irregular ridge or hill of stratified glacial drift deposited by glacial meltwater .
kettle : Depression left after the melting of a detached mass of glacier ice buried in drift .
lacustrine : Sediments that have settled from suspension in bodies of standing fresh water, or that hav e
accumulated at their margins through wave action . These sediments range in composition from sands t o
clays .
land : The solid part of the earth's surface or any part thereof . A tract of land is defined geographically as a
specific area of the earth's surface . Its characteristics embrace all reasonably stable, or predictably cyclic ,
attributes of the biosphere vertically above and below this area, including those of the atmosphere, the soil ,
and the underlying geology, the hydrology, the plant and animal populations, and the results of past an d
present human activity, to the extent that these attributes exert a significant influence on the present an d
future' uses of land by man .
land classification : The arrangement of land units into various categories based on the properties of the lan d
or its suitability for some particular purpose .
landforms : The various shapes of the land surface resulting from a variety of actions such as deposition o r
sedimentation (eskers, lacustrine basins), erosion (gullies, canyons), and earth crust movement s
(mountains) .
landscape : All features such as fields, hills, forests, and water that distinguish one part of the earth's surfac e
' from another part . Usually it is the portion of land or territory that the eye can see in a single view, includin g
all its natural characteristics .
leaching : The removal from the soil of materials in solution . See also eluviation .
levee : A natural or artificial embankment along a river or stream .
liquid limit (upper plastic limit, Atterberg limit) : (i) The water content corresponding to an arbitrary limi t
between the liquid and plastic states of consistence of a soil . (ii) The water content at which a pat of soil, cu t
by a standard-sized groove, will flow together for a distance of 12 mm under the impact of 25 blows in a
standard liquid-limit apparatus .
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