Glossary of Terms in Soil Science

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

saline alkali soil

(1) A soil containing enough exchangeable sodium to interfere with the growth of most crop plants, and containing appreciable quantities of soluble salts. The exchangeable-sodium percentage is greater than 15, the conductivity of the saturation extract is greater than 4 mmhos/cm at 25øC, and the pH is usually 8.5 or less in the saturated soil. (2) A saline-alkali soil has a combination of harmful quantities of salts and either a high alkalinity or high content of exchangeable sodium, or both, so distributed in the profile that the growth of most crop plants is reduced. It is also called saline-sodic soil.

saline soil

A nonalkali soil that contains enough soluble salts to interfere with the growth of most crop plants. The conductivity of the saturation extract is greater than 4 mmhos/cm, the exchangeable-sodium percentage is less than 15, and the pH is usually less than 8.5.

salinity soil

The amount of soluble salts in a soil, expressed in terms of percentage, parts per million or other convenient ratios.

salinization

The process of accumulation of salts in soil.

salt-affected soil

Soil that has been adversely modified for the growth of most crop plants by the presence of certain types of exchangeable ions or of soluble salts. It includes soils having an excess of salts, or an excess of exchangeable sodium or both. See also saline-alkali soil, saline soil and sodic soil.

sand

A soil particle between 0.05 and 2.0 mm in diameter. Any one of five soil separates: very coarse sand, coarse sand, medium sand, fine sand or very fine sand. See also separates / soil. A soil textural class. See also texture, soil.

sandy

Containing a large amount of sand. It may be applied to any one of the soil classes that contains a large percentage of sand. See also class, soil and texture, soil.

sandy clay

A soil textural class. See also class, soil and texture, soil.

sandy clay loam

A soil textural class. See also class, soil and texture, soil.

sandy loam

A soil textural class. See also class, soil and texture, soil.

saturate

(1) To fill all the voids between soil particles with a liquid. (2) To form the most concentrated solution possible under a given set of physical conditions in the presence of an excess of the solute. (3) To fill to capacity, as the adsorption complex with a cation species; for example, H-saturated .

saturation extract

The extract from a soil sample that has been saturated with water.

science; soil

The science dealing with soil as a natural resource. It includes: soil formation, classification and mapping; the physical, chemical and biological properties of soils and the management of soils for various purposes such as the production of agricultural and forest crops, the construction of roads and others.

second bottom

The first terrace above the normal flood plain of a stream.

secondary mineral

A mineral resulting from the decomposition of a primary mineral or from the precipitation of the products of decomposition of a primary mineral. See also primary mineral.

sedimentary rock

A rock formed from materials deposited from suspension or precipitated from solution and usually more or less consolidated. The principal sedimentary rocks are sandstones, shales, limestones and conglomerates.

seepage

(1) The escape of water downward through the soil. (2) The emergence of water from the soil along an extensive line of surface in contrast to a spring where the water emerges from a local spot.

self-mulching soil

A soil in which the surface layer becomes so well aggregated that it does not crust and seal under the impact of rain but instead serves as a surface mulch when it dries.

sensitivity

The effect of remolding on the shear strength of an undrained cohesive soil.

separates (soil)

Mineral particles, less than 2.0 mm in equivalent diameter, ranging between specified size limits. The names and size limits of separates recognized by pedologists in Canada and the United States are: (1) very coarse sand, 2.0 to 1.0 mm; (2) coarse sand, 1.0 to 0.5 mm; (3) medium sand, 0.5 to 0.25 mm; (4) fine sand, 0.25 to 0.10 mm; (5) very fine sand, 0.10 to 0.05 mm; (6) silt,0.05 to 0.002 mm; (7) clay, less than 0.002 mm; and (8) fine clay, less than 0.0002 mm. The separates recognized by the International Society of Soil Science are: (1) coarse sand, 2.0 to 0.2 mm; (2) fine sand, 0.2 to 0.02 mm; (3) silt, 0.02 to 0.002 mm; and (4) clay, less than 0.002 mm.

sequum

A sequence of an eluvial horizon and its related illuvial horizon in a soil.

serial dilution

Successive dilution of a specimen, for example, 1:10 dilution equals 1 ml of a specimen plus 9 ml of diluent (e.g., sterile water); 1:100 dilution equals 1 ml of a 1:10 dilution plus 9 ml of diluent.

series (soil)

A category in the Canadian system of soil classification. This is the basic unit of soil classification and consists of soils that are essentially alike in all major profile characteristics except the texture of the surface.

shaly

(1) Containing a large amount of shale fragments. (2) A soil phase; for example shaly phase. (3) Kind of fragment see coarse fragments.

shear stress

The force per unit area acting tangentially to a given plane within a soil mass.

sheet erosion

The removal of a fairly uniform layer of soil from the land surface by runoff water.

sheet erosion

See erosion (2.).

silica-alumina ratio

The molecules of silicon dioxide (SiO2) per molecule of aluminum oxide (Al203) in clay minerals or soils.

silica-sesquioxide ratio

The molecules of silicon dioxide (SiO2) per molecule of aluminum oxide (Al203) plus ferric oxide (Fe203) in clay minerals or soils.

silt

(1) A soil separate consisting of particles between 0.05 and 0.002 mm in equivalent diameter. See also separates, soil. (2) A soil textural class. See also texture, soil.

silt loam

A soil textural class. See also texture, soil and class, soil.

silting

The deposition of water-borne sediments in stream channels, lakes, reservoirs or on floodplains usually resulting from a decrease in the velocity of the water.

siltstone

A very fine grained, consolidated. clastic rock composed predominantly of particles of silt grade.

silty clay

A soil textural class. See also texture / soil and class / soil.

silty clay loam

A soil textural class. See also texture, soil and class, soil.

single-grain structure

A soil structure in which the soil particles occur almost completely as individual or primary particles; secondary particles or aggregates are seldom present. It is usually found only in extremely coarse-textured soils.

site

(1) In ecology, an area described or defined by its biotic, climatic, and soil conditions in relation to its capacity to produce vegetation. (2) An area sufficiently uniform in biotic, climatic and soil conditions to produce a particular vegetation.

site index

(1) A quantitative evaluation of the productivity of a soil for forest growth under the existing or specified environment. (2) The height in feet of the dominant forest vegetation taken at or calculated to an index age usually 50 or 100 years.

sixty-centimetre tension

See moisture tension, soil.

skeletal

Rock and mineral particles larger than two mm occupy 35% or more but less than 90% (by volume)

slaking (soil)

The breakdown of aggregates resulting from the addition of water to soil.

slaty

Containing a considerable quantity of slate fragments. It is used to modify soil texture class names such as slaty clay loam. See also coarse fragments.

slick spots

Small areas in a field that are slick when wet, because of a high content of alkali or exchangeable sodium.

slickens

Fine-textured materials separated in placer mining and in ore-mill operations; the materials may be detrimental to plant growth and so should be confined in specially constructed basins. A miscellaneous land type.

slickenside

Smoothed surfaces along planes of weakness resulting from the movement of one mass of soil against another in soils dominated by swelling clays.

smectite

See montmorillonite group.

sodic soil

(1) A soil containing sufficient sodium to interfere with the growth of most crop plants. (2) A soil having an exchangeable-sodium percentage of 15 or more.

soil (1)

(1) The unconsolidated material on the immediate surface of the earth that serves as a natural medium for the growth of land plants.

soil (2)

(2) The naturally occurring unconsolidated material on the surface of the earth that has been influenced by parent material, climate (including the effects of moisture and temperature), macro- and micro-organisms and relief all acting over a period of time to produce soil that may differ from the material from which it was derived in many physical, chemical, mineralogical, biological and morphological properties.

soil (3)

(3) For the purpose of the Canadian taxonomic system, the earth's surface (the material that is to be classified) is divided into soil and nonsoil. Soil is the naturally occurring unconsolidated mineral or organic material at the earth's surface that is capable of supporting plant growth. It extends from the surface to 15 cm (6 inches) below the depth at which properties produced by soil-forming processes can be detected. These properties differ from those found in any underlying unconsolidated material. The soil-forming processes are defined as an interaction between climate, living organisms and relief acting on soil and soil parent material. Unconsolidated material includes material cemented or compacted by soil-forming processes. Soil may have water covering its surface to a depth of 60 cm (24 inches) or less in the driest part of the year. See also nonsoil.

soil moisture tension

In soils partially saturated with water there is moisture tension, which is equal in magnitude but opposite in sign to the soil water pressure. Moisture tension is equal to the pressure that must be applied to the soil water to bring it to a hydraulic equilibrium through a porous permeable wall or membrane with a pool of water of the same composition. See also water / soil The pressures used and the corresponding percentages most commonly determined are: - 15-atmosphere percentage, - 15-bar percentage, - 1/3-atmosphere percentage, - 1/3-bar percentage, - 60-centimetre percentage.

soil-formation factors

The variable, usually interrelated natural agencies that are responsible for the formation of soil. The factors are: parent rock, climate, organisms, relief, and time.

solclime

The temperature and moisture conditions of the soil; the soil climate.

solifluction

A type of creep that takes place in regions where the ground freezes to a considerable depth and as it thaws during the warm seasons the upper thawed position creeps downhill over the frozen material. The soil moves as a viscous liquid down slopes of as little as 2 or 3 degrees and may carry rocks of considerable size in suspension.

Solod

A great group of soils in the Solonetzic order occurring most commonly in the grassland and parkland regions. The soils have a dark-colored surface (Ah) horizon; a prominent eluvial (Ahe or Ae) horizon at least 5 cm (2 inches) thick, a prominent transitional (AB) horizon that breaks readily into blocky aggregates and a darkly stained B (Bnt) horizon over a C horizon that is saline and usually calcareous.

solodized soil

A soil that has been subjected to the processes responsible for the development of a Solod and has at least some of the characteristics of a Solod.

Solodized Solonetz

A great group of soils in the Solonetzic order, occurring most commonly in the grassland and parkland regions and consisting of soils with a variable surface (Ah, Ahe, or Ae) horizon that is underlain by a well-developed Ae horizon, a compact prismatic or columnar Bnt horizon, and a C horizon that is saline and usually calcareous.

Solonetz

A great group of soils in the Solonetzic order, occurring most commonly in the grassland and parkland regions and consisting of soils with a variable surface (Ah, Ahe, or Ae) horizon that breaks abruptly into a hard, compact prismatic or columnar B (Bnt, rarely a Bn) horizon underlain by one or more saline and usually calcareous (Bs, Cs, Csa, Csk, Cca) horizons. They lack a continuous Ae horizon 2.5 cm (1 inch) or more thick.

Solonetzic

An order of soils developed mainly under grass or grass-forest vegetative cover in semiarid to subhumid climates. The soils have a stained brownish solonetzic B (Bnt or Bn) horizon and a saline C horizon. The surface may be one or more of Ap, Ah or Ae horizons. See also: Solonetzic Soil Classification.