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:

Name of separate Diameter (mm)
very coarse sand 2.0-1.0
coarse sand 1.0-0.5
medium sand 0.5-0.25
fine sand 0.25-0.10
very fine sand 0.10-0.05
silt 0.05-0.002
clay ≤0.002
fine clay ≤0.0002

9-1 Terminology for rounded and subrounded coarse fragments.
Size and name of fragments
Up to 8 cm in diameter 8-25 cm in diameter >25 cm in diameter
[1] Bouldery is sometimes used where stones are larger than 60 cm.
Gravelly Cobbly Stoney (or bouldery) [1]

9-2 Terminology for Irregularly shaped angular coarse fragments.
Kind of fragments Size and name of fragments
Up to 8 cm in diameter 8-25 cm in diameter >25 cm in diameter
Chert Cherty Coarse cherty Stony
Other than chert Angular gravelly Angular cobbly Stony

9-3 Terminology for thin flat coarse fragments.
Kind of fragments Size and name of fragments
Up to 15 cm in diameter 15-38 cm in diameter >38 cm in diameter
Thin flat sandstone, limestone, and schist Channery Flaggy Stony
Slate Slaty Flaggy Stony
Shale Shaly Flaggy Stony

Description of this image follows

Figure 42 Soil texture classes triangle. Percentages of clay and sand in the main textural classes of soil; the remainder of each class is silt. Abbreviations for the texture classes are: HC, heavy clay; C, clay; SiC, silty clay; SiCL, silty clay loam; CL, clay loam; SC, sandy clay; SiL, silt loam; L, loam; SCL, sandy clay loam; SL, sandy loam; Si, silt; LS, loamy sand; S, sand.

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
Subangular blocky: faces subrectangular, vertices mostly oblique, or subrounded Fine subangular blocky
Medium subangular blocky
Coarse subangular blocky
Very coarse subangular blocky
Granular: spheroidal and characterized by rounded vertices Fine granular
Medium granular
Coarse granular
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
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
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

Description of this image precedes (see table 10).

Figure 43 Type, kinds, and classes of soil structure.

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