[The Cooperative Soil Survey] Soils Tutorial: Glossary

Glossary

Definitions from the Soil Science Society of America (SSSA)

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

Pan A compact, dense layer in a soil that impedes the movement of water and growth of roots. For example, hardpan, fragipan, claypan, plowpan, and traffic pan.

Parent material The unconsolidated organic and mineral material in which soil forms.

Ped An individual natural soil aggregate, such as a granule, a prism, or a block.

Pedisediment Fine textured sediment that is similar in composition to the constituents of the underlying material.

Pedon The smallest volume that can be called "a soil." A pedon is three dimensional and large enough to permit study of all horizons. Its area ranges from about 10 to 100 square feet (1 square meter to 10 square meters), depending on the variability of the soil.

Percolation The downward movement of water through the soil.

Percs slowly The slow movement of water through the soil, adversely affecting the specified use.

Permeability The quality of the soil that enables water to move downward through the profile. Permeability is measured as the number of inches per hour that water moves downward through the saturated soil.

pH value A numerical designation of acidity and alkalinity in soil (See Reaction, soil).

Phase soil A subdivision of a soil series based on features that affect its use and management. For example, slope, stoniness, and thickness.

Piping Formation of subsurface tunnels or pipelike cavities by water moving through the soil.

Plastic limit The moisture content at which a soil changes from semisolid to plastic.

Plasticity index The numerical difference between the liquid limit and the plastic limit. The range of moisture content within which the soil remains plastic.

Plowpan A compacted layer formed in the soil directly below the plowed layer.

Polypedon A volume of soil having properties within the limits of a soil series, the lowest and most homogeneous category of soil taxonomy. A soil individual.

Ponding Standing water on soils in closed depressions. Unless the soils are artificially drained, the water can be removed only by percolation or evapotranspiration.

Poor filter Because of rapid permeability the soil may not adequately filter effluent from a waste disposal system.

Poorly graded Refers to a coarse grained soil or soil material consisting mainly of particles of nearly the same size Because there is little difference in size of the particles, density can be increased only slightly by compaction.

Productivity soil The capability of a soil for producing a specified plant or sequence of plants under specific management.

Profile soil A vertical section of the soil extending through all its horizons and into the parent material.

Pan	A compact, dense layer in a soil that impedes the movement of water and growth of roots. For example, hardpan, fragipan, claypan, plowpan, and traffic pan.
Parent material	The unconsolidated organic and mineral material in which soil forms.
Ped	An individual natural soil aggregate, such as a granule, a prism, or a block.
Pedisediment	Fine textured sediment that is similar in composition to the constituents of the underlying material.
Pedon	The smallest volume that can be called "a soil." A pedon is three dimensional and large enough to permit study of all horizons. Its area ranges from about 10 to 100 square feet (1 square meter to 10 square meters), depending on the variability of the soil.
Percolation	The downward movement of water through the soil.
Percs slowly	The slow movement of water through the soil, adversely affecting the specified use.
Permeability	The quality of the soil that enables water to move downward through the profile. Permeability is measured as the number of inches per hour that water moves downward through the saturated soil.
pH value	A numerical designation of acidity and alkalinity in soil (See Reaction, soil).
Phase soil	A subdivision of a soil series based on features that affect its use and management. For example, slope, stoniness, and thickness.
Piping	Formation of subsurface tunnels or pipelike cavities by water moving through the soil.
Plastic limit	The moisture content at which a soil changes from semisolid to plastic.
Plasticity index	The numerical difference between the liquid limit and the plastic limit. The range of moisture content within which the soil remains plastic.
Plowpan	A compacted layer formed in the soil directly below the plowed layer.
Polypedon	A volume of soil having properties within the limits of a soil series, the lowest and most homogeneous category of soil taxonomy. A soil individual.
Ponding	Standing water on soils in closed depressions. Unless the soils are artificially drained, the water can be removed only by percolation or evapotranspiration.
Poor filter	Because of rapid permeability the soil may not adequately filter effluent from a waste disposal system.
Poorly graded	Refers to a coarse grained soil or soil material consisting mainly of particles of nearly the same size Because there is little difference in size of the particles, density can be increased only slightly by compaction.
Productivity soil	The capability of a soil for producing a specified plant or sequence of plants under specific management.
Profile soil	A vertical section of the soil extending through all its horizons and into the parent material.