Soils of the - Agriculture and Agri-Food Canada

oulders : Rock fragments over 60 cm (2 ft) in diameter . In engineering practice boulders are greater than 2 0
cm (8 inches) in diameter.
Brunisolic : An order of soils whose horizons are developed sufficiently to exclude the soils from the Regosoli c
order, but that lack the degrees or kinds of horizon development specified for soils of the other orders .
These soils, which occur under a wide variety of climatic and vegetative conditions, all have Bm or Bt j
horizons . The great groups Melanic Brunisol, Eutric Brunisol, Sombric Brunisol, and Dystric Bruniso l
belong to this order.
bulk density, soil : The mass of dry soil per unit bulk volume . The bulk volume is determined before the soil i s
dried to constant weight at 105° C .
calcareous soil : Soil containing sufficient calcium carbonate, often with magnesium carbonate, to effervesc e
visibly when treated with cold 0 .1 N hydrochloric acid .
capability class : A rating that indicates the capability of land for some use such as agriculture, forestry ,
recreation, or wildlife .
capability subclass : A grouping of lands that have similar kinds of limitations and hazards . It provide s
information on the kind of conservation problem or limitation . The class and subclass together provid e
information about the degree and kind of limitation .
carbon-nitrogen ratio : The ratio of the weight of organic carbon to the weight of total nitrogen in a soil or in a n
organic material .
category : A grouping of related soils defined at approximately the same level of abstraction . In the Canadia n
soil classification the categories are order, great group, subgroup, family, and series .
cation exchange : The interchange of a cation in solution and another cation on the surface of any surface -
active material such as clay colloid or organic colloid .
cation exchange capacity : The total amount of exchangeable cations that a soil can adsorb . It is expresse d
in milliequivalents per 100 g of soil or other adsorbing materials such as clay .
cemented-indurated : Having a hard, brittle consistence because the particles are held together by cement -
ing substances such as humus, calcium carbonate, or the oxides of silicon, iron, and aluminum . Th e
hardness and brittleness persist even when the soil is wet .
Chernozemic : An order of soils that have developed under xerophytic or mesophytic grasses and forbs, o r
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 . Th e
order consists of the Brown, Dark Brown, Black, and Dark Gray great groups .
chroma : The relative purity, strength, or saturation of a colour . It is directly related to the dominance of th e
determining wavelength of light . It is one of the three variables of colour . See also Munsell colour system ;
hue ; and value, colour.
class, soil : A group of soils having a definite range in a particular property such as acidity, degree o f
slope, texture, structure, land-use capability, degree of erosion, or drainage .
classification, soil : The systematic arrangement of soils into categories on the basis of their characteristics .
Broad groupings are made on the basis of general characteristics, and subdivisions on the basis of mor e
detailed differences in specific properties .
clay : (i) As a particle-size term : a size fraction less than 0 .002 mm in equivalent diameter, or some other limi t
(geologists and engineers). (ii) As a rock term : a natural, earthy, fine grained material that develop s
plasticity with a small amount of water. (iii) As a soil term : a textural class in which the soil materials contai n
40 percent or more of clay. (iv) As a soil separate : a material usually consisting largely of clay minerals bu t
commonly also of amorphous free oxides and primary minerals .
clay films (skins) : Coatings of oriented clays on the surfaces of soil peds and mineral grains, and in soil pores .
clay loam : Soil material that contains 27% to 40% clay and 20% to 45% sand .
clay mineral : Finely crystalline hydrous aluminum silicates and hydrous magnesium silicates with a phyllosili -
cate structure .
clayey : Containing large amounts of clay, or having properties similar to those of clay.
climatic moisture deficit : The negative difference between precipitation and the potential evapotranspiratio n
from May 1st to September 30th .
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