Soils of the - Agriculture and Agri-Food Canada

climatic moisture surplus : . The positive difference between precipitation and the potential evapotranspiratio n
from May 1st to September 30th .
climax: A plant community of the most advanced type capable of development under, and in dynami c
equilibrium with, the prevailing environment .
clod : A compact, coherent mass of soil produced by digging or plowing. Clods usually slake easily wit h
repeated wetting and drying .
coarse fragments : Rock or mineral particles greater than 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 .
cobble : Rounded or partially rounded rock or mineral fragment 7 .5 to 25 cm (3 to 10 inches) in diameter . I n
engineering practice, cobbles are greater than 7 .5 cm (3 inches) but less than 20 cm (8 inches) i n
diameter.
colluviium : Product of mass wasting ; materials that have reached their present position by direct, gravit y
induced movement .
complex, soil : A mapping unit used in detailed and reconnaissance soil surveys where two or more define d
soil units are so intimately intermixed geographically that it is impractical, because of the scale used, t o
separate them .
Concretion : A mass or concentration of a chemical compound, such as calcium carbonate or iron oxide, in th e
form of a grain or nodule of varying size, shape, hardness, and color, found in soil and in rock . The term i s
sometimes restricted to concentrations having concentric fabric . The composition of some concretions i s
unlike that of the surrounding material .
consistence : (i) The resistance of a material to deformation or rupture . (ii) The degree of cohesion or adhesio n
of the soil mass . Terms used for describing consistence at various soil moisture contents are :
wet soil-nonsticky, slightly sticky, sticky, and very sticky ; nonplastic, slightly plastic, plastic, and ver y
plastic .
moist soil-loose, very friable, friable, firm, and very firm ; compact, very compact, and extremel y
compact .
dry soil-loose, soft, slightly hard, hard, very hard, and extremely hard .
cementation-weakly cemented, strongly cemented, and indurated .
creep, soil : An imperceptibly slow, more or less downward and outward movement of soil or rock on slope s
due mainly to gravity. The movement is essentially viscous, under shear stresses sufficient to produc e
permanent deformation but too small to produce shear failure, as in a landslide .
Cryosolic : An order of soils in the Canadian taxonomic system . Cryosolic soils are mineral or organic soils tha t
have perennially frozen material within 1 m (3 ft) of the surface in some part of the soil body, or pedon . Th e
mean annual soil temperature is less than 0° C (32° F) . They are the dominant soils of the zone of continuou s
permafrost and become less widespread to the south in the zone of discontinuous permafrost ; thei r
maximum development occurs in organic and poorly drained, fine textured materials .
degradation : The changing of a soil to a more highly leached and weathered state, usually accompanied b y
morphological changes such as the development of an eluviated, light-coloured A (Ae) horizon .
delta : An area at the mouth of a river formed by deposition of successive layers of sediments brought dow n
from the land and spread out on the bottom of a basin . Where the stream current reaches quiet water, th e
bulk of the coarser load is dropped and the finer material is carried farther out .
deposit : Material left in a new position by a natural transporting agent such as water, wind, ice, or gravity, or b y
the activity of man .
drain : (i) To provide channels, such as open ditches or drain tile, so that excess water can be removed by
surface or by internal flow. (ii) To lose water from the soil by percolation .
dunes : Wind-built ridges and hills of sand .
duric : A soil horizon tht is strongly cemented and usually has an abrupt upper boundary and a diffuse lowe r
boundary. Cementation is usually strongest near the upper boundary . Air-dried clods do not slake whe n
immersed in water.
ecology : The study of the relationship between organisms and their environment .
eluvial horizon : A soil horizon that has been formed by the process of eluviation .
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