Soils - Part 1: The Origin and Development of Soil (How Soil Gets a Life and a Name) Glossary

(Capacity) The amount of water released between in situ field capacity and the permanent wilting point (usually estimated by water content at soil matric potential of –1.5 Mpa). Available water is not the portion of water that can be absorbed by plant roots, which is plant specific. (Soil Science Society of America, 1997, p. 9)

As a soil separate, clay refers to mineral soil particles which are less than 0.02 millimeters in diameter. As a soil textural class, clay refers to soil material that is 40 percent or more clay, less than 45 percent sand, and less than 40 percent silt.

Precipitation, temperature and other aspects of climate affect how specific soils are formed.

Land on which the vegetation is dominated by grasses, grasslike plants, and/or forbs. Herbaceous vegetation provides at least 80% of the canopy cover.

The layers of soil, usually three, which make up the soil profile. Soil horizons differ in color, texture, structure and organic matter content. The A Horizon is the upper surface or topsoil and usually has the highest organic matter content; the B Horizon is the subsoil; and the C Horizon is the parent material. A given soil may have one or all three horizons.

A naturally occurring material composed of carbonates of calcium and magnesium.

Material that contains carbon and is found in the soil. Most soil organic matter comes from previously living organisms.  Temperature and moisture are the two main factors affecting its development.

Rock or minerals which are weathered to form smaller particles of a soil. Parent material is one of the five factors contributing to formation of a specific soil. In the Great Plains, much parent material is associated with ancient seas or glacier deposits.

The shape of a slope profile. Profile is the slope viewed in a vertical cross-section.

Individual rock or mineral fragments in a soil that range from 0.05 to 2.0 millimeters in diameter. Most sand grains consist of quartz, but they can be of any mineral composition.  Sand is also the textural class name of any soil that contains 85 percent or more sand and no more than 10 percent clay.

A soil inorganic separate in the range of 2 to 50 micrometers (or 0.002 to 0.05 mm.). Silt is smaller than sand but larger than clay.

The top layer of the Earth’s surface, consisting of four major components: air, water, organic matter and mineral matter. There are three categories of soil particles--sand, silt and clay--which are called "soil separates."

Determined by the amount of weathering that has occurred; to what extent the parent material has been converted to distinct horizons or soil layers.  Usually described as young, mature or old.

Determined by the amount of weathering that has occurred; to what extent the parent material has been converted to distinct horizons or soil layers.  Usually described as young, mature or old.

A specific soil is classified according to the number of horizons in its soil profile and the soil properties of each horizon. Well developed soils are old and contain all three master horizons (A, B, and C), as well as several subdivisions of the master horizons.

A specific soil is classified according to the number of horizons in its soil profile and the soil properties of each horizon. Well developed soils are old and contain all three master horizons (A, B, and C), as well as several subdivisions of the master horizons.

Five factors influence the development of a specific soil:  parent material, climate, living organisms, topography and time.

A unit of soil classification determined by studying horizon characteristics, such as: number of horizons, color, thickness, texture, erosion phase, slope, organic content and depth to hardpan. All soils given the same soil series name possess the same characteristics across the landscape.

The arrangement of soil separates into units called soil aggregates.

The combination or arrangement of soil particles that forms peds or aggregates.

Physical earthen barriers to runoff and can be very effective in reducing P losses to erosion and runoff.

The ability of a soil to hold water; varies by soil texture. Medium textured soils (fine sandy loam, silt loam and silty clay loam) have the highest water-holding capacity.

The means by which soil, rocks and minerals are changed by physical and chemical processes into other soil components.  Weathering is an integral part of soil development.