Chapter 17: Terminology for Describing Soils

This chapter provides a brief summary of the main terminology used to describe soils at the scales of the landscape and pedon. It refers to the section of the Canadian Soil Information System (CanSIS) Manual for Describing Soils in the Field 1982 Revised in which the terminology and methods of coding descriptive data are defined in detail.

Landform and relief  See section 8B in the Manual and Chapter 18 in this publication.

Erosion  See section 8H in the Manual and Chapter 15 in this publication for definitions of water and wind erosion classes.

Stoniness  See section 8J in the Manual and Chapter 15 herein for definitions of stoniness classes. Terminology for coarse fragments is given in Table 9.

Rockiness (bedrock exposure)  See section 8K in the Manual and Chapter 15 herein for definitions of rockiness classes.

Soil water regime  See sections 8D, D1, D2, E, F, and G in the Manual. The following aspects of the soil water regime are classified: Soil Drainage, Aridity, Hydraulic Conductivity, Impeding Layer, Depth of Saturated Zone and Duration, and Man-made Modifiers.

Soil color  See section 10C in the Manual. Munsell notations, e.g., 10YR 5/3, (hue, value, and chroma) as well as the appropriate color name (shown for the notation given) are used to indicate the colors of individual horizons of the pedon. Preferably record both moist (10YR 3/3 m) and dry (10YR 5/3 d) soil colors and indicate whether the sample is moist (m) or dry (d) if color is recorded at only one moisture state.

Soil texture  See section 10K in the Manual. Textural classes are defined in terms of the size distribution of primary particles as estimated by sieve and sedimentation analysis. The textural classes are indicated in Figure 42; named size classes of primary particles and their dimensions are as follows:

Mottles  See section 10L in the Manual. Mottles are spots or blotches of different color, or shade of color, interspersed with the dominant soil color. Note the color of the matrix and the principal mottles, and the pattern of mottling. The latter is indicated in terms of abundance (few, common, many), size (fine, medium, coarse), and contrast with the matrix (faint, distinct, prominent).

Soil structure  See section 10M in the Manual. Soil structure refers to the aggregation of primary soil particles into compound particles that are separated from adjoining aggregates by surfaces of weakness. Soil structure is classified in terms of grade or distinctness (weak, moderate, strong), class or size (fine, medium, coarse, very coarse), and type (granular, platy, prismatic, blocky). See Table 10 and Figure 43.

Consistence  See section 10N in the Manual. Soil consistence refers to the soils resistance to deformation or rupture and its degree of cohesion and adhesion. Consistence of wet soil is classified in terms of stickiness (nonsticky, slightly sticky, sticky, or very sticky) and plasticity (nonplastic, slightly plastic, plastic, or very plastic). Consistence is classified for moist soil as loose, very friable, friable, firm, or very firm. For dry soil consistence is classified as loose, soft, slightly hard, hard, very hard, extremely hard, or rigid. Cementation refers to brittle, hard consistence due to some cementing substance. The classes of cementation are weakly cemented, strongly cemented, and indurated.

Roots  See section 10T in the Manual. Abundance, size, orientation, distribution, and depth of root penetration are noted.

Pores  See section 10U in the Manual. Abundance, size, orientation, distribution, continuity, morphology, and type of pore are estimated and noted.

Clay films (argillans)  See section 10S in the Manual. Clay films are described in terms of frequency, thickness, location, and color.

Horizon boundary  See section 10P in the Manual. The lower boundary of each horizon is described in terms of distinctness (abrupt, clear, gradual, or diffuse) and form (smooth, wavy, irregular, or broken).

Ice  See Pihlainen and Johnston (1963), Brown and Kupsch (1974), and Harris et al. (1988) for terminology that describes ice and other features of permafrost soils.

Other features  See sections 8 and 10 in the Manual. Some other features of soils and sites that may be described are humus form, permafrost, land use, concretions, nodules, calcareousness, salinity, coarse fragments, and reaction.

Example of a Pedon Description

Descriptive data for soils are commonly entered on CanSIS forms, but conventional descriptions are needed for some purposes. The following order of listing properties is recommended: color, texture, mottles, structure, consistence, roots, pores, clay films, concretions, carbonates, salts, coarse fragments, horizon boundary, thickness range, and reaction. A description of a Gleyed Humo-Ferric Podzol follows:

Horizon	Depth (cm)	Description
L-H	7.5-0	Black (10YR 2/1 m), dark grayish brown (10YR 4/1 d); semi-decomposed organic matter; fibrous, abundant, fine and medium roots; abrupt, smooth boundary; 5-10 cm thick; acid.
Ae	0-10	Gray (5YR 6/1 m), light gray (5YR 7/1 d); sandy loam; single grain; loose, friable; few, fine and medium roots; few, fine, vesicular pores; clear, wavy boundary with some fine tongues into underlying horizon; 5-12 cm thick; acid.
Bfgj	10-30	Reddish brown (5YR 4/4 m, 5/4 d); sandy loam; common, medium, distinct strong brown (7.5 YR 5/6) mottles; amorphous; friable; few, fine and very fine roots; few, medium and fine pores; some gravel; clear, smooth boundary; 15-25 cm thick; acid.
Bfg	30-61	Reddish brown (5YR 4/3 m, 5/3 d); sandy loam; many, medium to coarse, prominent strong brown (7.5 YR 5/6) mottles; amorphous; firm; few stones; clear, smooth boundary; 20-38 cm thick; acid.
C	61+	Reddish brown (2.5YR 4/4 m, 5/4 d) sandy loam; amorphous; firm; slightly plastic; some stones; acid.

Table 10 Types and classes of soil structure

Type	Kind	Class	Size (mm)
Structureless: no observable aggregation or no definite orderly arrangement around natural lines of weakness	Single grain structure: loose, incoherent mass of individual particles as in sands
	Amorphous (massive) structure: a coherent mass showing no evidence of any distinct arrangement of soil particles
Blocklike: soil particles are arranged around a point and bounded by flat or rounded surfaces	Blocky (angular blocky): faces rectangular and flattened, vertices sharply angular	Fine blocky Medium blocky Coarse blocky Very coarse blocky	<10 10-20 20-50 >50
	Subangular blocky: faces subrectangular, vertices mostly oblique, or subrounded	Fine subangular blocky Medium subangular blocky Coarse subangular blocky Very coarse subangular blocky	<10 10-20 20-50 >50
	Granular: spheroidal and characterized by rounded vertices	Fine granular Medium granular Coarse granular	<2 2-5 5-10
Platelike: soil particles are arranged around a horizontal plane and generally bounded by relatively flat horizontal surfaces	Platy structure: horizontal planes more or less developed	Fine platy Medium platy Coarse platy	<2 2-5 >5
Prismlike: soil particles are arranged around a vertical axis and bounded by relatively flat vertical surfaces	Prismatic structure: vertical faces well defined, and edges sharp	Fine prismatic Medium prismatic Coarse prismatic Very coarse prismatic	<20 20-50 50-100 >100
	Columnar structure: vertical edges near top of columns not sharp; columns flat-topped, round-topped or irregular	Fine columnar Medium columnar Coarse columnar Very coarse columnar	<20 20-50 50-100 >100

Source: The Canadian System of Soil Classification (Third Edition)