Glossary of Terms in Soil Science

L layer

See horizon / soil.

lacustrine deposit

Material deposited in lake water and later exposed either by lowering of the water level or by uplifting of the land. These sediments range in texture from sands to clays.

lagg

The depressed margin of a raised bog.

lamina

A unit layer less than 1 cm thick in a stratified sequence.

land

The solid part of the earth's surface or any part thereof. A tract of land is defined geographically as a specific area of the earth's surface. Its characteristics embrace all reasonably stable, or predictably cyclic, attributes of the biosphere vertically above and below this area, including those of the atmosphere, the soil and the underlying geology, the hydrology, the plant and animal populations, and the results of past and present human activity to the extent that these attributes exert a significant influence on the present and future uses of land by man.

land classification

The arrangement of land units into various categories based on the properties of the land or its suitability for some particular purpose.

land type

See association/ soil.

landforms

The various shapes of.the land surface resulting from a variety of actions such as deposition or sedimentation (eskers, lacustrine basins), erosion (gullies, canyons) and earth crust movements (mountains).

landscape

All the natural features such as fields, hills, forests, and water that distinguish one part of the earth's surface from another part. Usually it is the portion of land or territory that the eye can see in a single view, including all its natural characteristics.

landslide (landslip)

(1) A mass of material that has slipped downhill by gravity, often assisted by water when the material is saturated. (2) Rapid movement of a mass of soil, rock, or debris down a slope.

latitude zonation

Latitudinal (normal) zonation of soils. See also vertical zonation.

lattice energy

The energy required to separate the ions of a crystal to an infinite distance from each other.

lattice structure

The orderly arrangement of atoms in a crystalline material.

leaching

The removal from the soil of materials in solution. See also eluviation.

levee

A natural or artificial embankment along a river or stream.

lichen

A symbiotic, mutualistic association of an algal type and a fungal type.

lime concretion

An aggregate of precipitated calcium carbonate or other material cemented by precipitated calcium carbonate.

lime potential

The negative logarithm of the ratio of the hydrogen ion activity to the square root of the sum of the activities of calcium and magnesium in the soil solution. It is generally written as pH - 1/2p(Ca + Mg). It can also be written as 1/2 log [(Ca + Mg)(OH)2] + pKw, where Kw is the ionic product of water. Lime potential is an expression of the sum of the activities of calcium and magnesium hydroxides in the soil solution. See also corrected lime potential.

lime requirement

The amount of agricultural limestone, or the equivalent of another liming material, required per hectare to a soil depth of 15 cm (or for 2240 t of soil) to raise the pH of the soil to a specific value under field conditions.

lime, agricultural

A soil amendment consisting principally of calcium carbonate, and including magnesium carbonate and perhaps other materials. It is used to supply calcium and magnesium as essential elements for growth of plants and to neutralize soil acidity.

limno layer

In organic soil, a layer at least 5 cm (2 inches) thick composed of marl, diatomaceous earth, or coprogenous earth (sedimentary peat).

liquefaction (spontaneous liquefaction)

The sudden large decrease of the shearing resistance of a cohesionless soil. It is caused by a collapse of the structure by shock or other strain and is associated with a sudden, temporary increase of the interstitial water pressure. It involves a temporary transformation of the material into a fluid mass. See also quick clay.

liquid limit

(upper plastic limit, Atterberg limit) (1) The water content corresponding to an arbitrary limit between the liquid and plastic states of consistence of a soil. (2) The water content at which a pat of soil, cut by a standard-sized groove, will flow together for a distance of 12 mm under the impact of 25 blows in a standard liquid-limit apparatus.

lithic layer

Bedrock under the control section of a soil. In Organic soils, bedrock occurring within a depth of between 10 cm (4 inches) and 160 cm (64 inches) from the surface.

lithosequence

A group of related soils that differ from each other in certain properties primarily because of differences in the parent rock.

loam

A soil textural class. See also texture, soil.

loamy

Intermediate in texture and properties between fine-textured and coarse-textured soils. It includes all textural classes having ""loam"" or ""loamy"" as a part of the class name, such as clay loam or loamy sand. See also loam and texture, soil.

loamy fine sand

See texture / soil.

loamy sand

See texture/ soil.

loamy very fine sand

See texture, soil.

loess

Material transported and deposited by wind and consisting of predominantly silt-sized particles.

loose

A soil consistence term. See also consistence.

lower plastic limit

See plastic limit.

Luvic Gleysol

A great group of soils in the Gleysolic order developed under wet conditions, under grass or forest or both. The soils have Aeg and Btg horizons.

Luvisolic

An order of soils that have eluvial (Ae) horizons, and illuvial (Bt) horizons in which silicate clay is the main accumulation product. The soils developed under forest or forest-grassland transition in a moderafe to cool climate. See also: Luvisolic Soil Classification.

lysimeter

(1) A device for measuring percolation and leaching losses of water and solutes from a column of soil under controlled conditions. (2) A device for measuring gains (precipitation and condensation) and losses (evapotranspiration) of water by a column of soil.