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 (Agriculture Canada Expert Committee on Soil Survey 1983) 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:

Table 9. Terminology for various shapes and sizes of coarse fragments

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:

Table 10. Types and classes of soil structure