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Glossary (SS of Dade, Florida)

ABC soil.
A soil having an A, a B, and a C horizon.
AC soil.
A soil having only an A and a C horizon. Commonly, such soil formed in recent alluvium or on steep, rocky slopes.
Aeration, soil.
The exchange of air in soil with air from the atmosphere. The air in a well aerated soil is similar to that in the atmosphere; the air in a poorly aerated soil is considerably higher in carbon dioxide and lower in oxygen.
Aggregate, soil.
Many fine particles held in a single mass or cluster. Natural soil aggregates, such as granules, blocks, or prisms, are called peds. Clods are aggregates produced by tillage or logging.
Alkali (sodic) soil.
Soil having so high a degree of alkalinity (pH 8.5 or higher) or so high a percentage of exchangeable sodium (15 percent or more of the total exchangeable bases), or both, that plant growth is restricted.
Alluvium.
Material, such as sand, silt, or clay, deposited on land by streams.
Area reclaim (in tables).
An area difficult to reclaim after the removal of soil for construction and other uses. Revegetation and erosion control are extremely difficult.
Association, soil.
A group of soils geographically associated in a characteristic repeating pattern and defined and delineated as a single map unit.
Available water capacity (available moisture capacity).
The capacity of soils to hold water available for use by most plants. It is commonly defined as the difference between the amount of soil water at field moisture capacity and the amount at wilting point. It is commonly expressed as inches of water per inch of soil. The capacity, in inches, in a 60-inch profile or to a limiting layer is expressed as: 
Very low.......0 to 3 
Low............3 to 6 
Moderate.......6 to 9 
High...........9 to 12 
Very high......more than 12
Base saturation.
The degree to which material having cation-exchange properties is saturated with exchangeable bases (sum of Ca, Mg, Na, K), expressed as a percentage of the total cation-exchange capacity.
Bedding.
Controlling excess water in cropped areas through the use of regularly spaced, shallow ditches and beds.
Bedding planes.
Fine stratifications, less than 5 millimeters thick, in unconsolidated alluvial, eolian, lacustrine, or marine sediments.
Bedrock.
The solid rock that underlies the soil and other unconsolidated material or that is exposed at the surface.
Bisequum.
Two sequences of soil horizons, each of which consists of an illuvial horizon and the overlying eluvial horizons.
Bottom land.
The normal flood plain of a stream, subject to flooding.
Boulders.
Rock fragments larger than 2 feet (60 centimeters) in diameter.
Calcareous soil.
A soil containing enough calcium carbonate (commonly combined with magnesium carbonate) to effervesce visibly when treated with cold, dilute hydrochloric acid.
California bearing ratio (CBR).
The load-supporting capacity of a soil as compared to that of standard crushed limestone, expressed as a ratio. First standardized in California. A soil having a CBR of 16 supports 16 percent of the load that would be supported by standard crushed limestone, per unit area, with the same degree of distortion.
Capillary water.
Water held as a film around soil particles and in tiny spaces between particles. Surface tension is the adhesive force that holds capillary water in the soil.
Cation.
An ion carrying a positive charge of electricity. The common soil cations are calcium, potassium, magnesium, sodium, and hydrogen.
Cation-exchange capacity.
The total amount of exchangeable cations that can be held by the soil, expressed in terms of milliequivalents per 100 grams of soil at neutrality (pH 7.0) or at some other stated pH value. The term, as applied to soils, is synonymous with base-exchange capacity but is more precise in meaning.
Cement rock.
Shaly limestone used in the manufacture of cement.
Channery soil.
A soil that is, by volume, more than 15 percent thin, flat fragments of sandstone, shale, slate, limestone, or schist as much as 6 inches along the longest axis. A single piece is called a fragment.
Chiseling.
Tillage with an implement having one or more soil-penetrating points that shatter or loosen hard, compacted layers to a depth below normal plow depth.
Clay.
As a soil separate, the mineral soil particles less than 0.002 millimeter in diameter. As a soil textural class, soil material that is 40 percent or more clay, less than 45 percent sand, and less than 40 percent silt.
Clay film.
A thin coating of oriented clay on the surface of a soil aggregate or lining pores or root channels. Synonyms: clay coating, clay skin.
Climax vegetation.
The stabilized plant community on a particular site. The plant cover reproduces itself and does not change so long as the environment remains the same.
Coarse fragments.
If round, mineral or rock particles 2 millimeters to 25 centimeters (10 inches) in diameter; if flat, mineral or rock particles (flagstone) 15 to 38 centimeters (6 to 15 inches) long.
Coarse textured soil.
Sand or loamy sand.
Cobblestone (or cobble).
A rounded or partly rounded fragment of rock 3 to 10 inches (7.6 to 25 centimeters) in diameter.
Complex, soil.
A map unit of two or more kinds of soil in such an intricate pattern or so small in area that it is not practical to map them separately at the selected scale of mapping. The pattern and proportion of the soils are somewhat similar in all areas.
Concretions.
Grains, pellets, or nodules of various sizes, shapes, and colors consisting of concentrated compounds or cemented soil grains. The composition of most concretions is unlike that of the surrounding soil. Calcium carbonate and iron oxide are common compounds in concretions.
Conservation tillage.
A tillage system that does not invert the soil and that leaves a protective amount of crop residue on the surface throughout the year.
Consistence, soil.
The feel of the soil and the ease with which a lump can be crushed by the fingers. Terms commonly used to describe consistence are:
  • Loose.—Noncoherent when dry or moist; does not hold together in a mass.
  • Friable.—When moist, crushes easily under gentle pressure between thumb and forefinger and can be pressed together into a lump.
  • Firm.—When moist, crushes under moderate pressure between thumb and forefinger, but resistance is distinctly noticeable.
  • Plastic.—When wet, readily deformed by moderate pressure but can be pressed into a lump; will form a "wire" when rolled between thumb and forefinger.
  • Sticky.—When wet, adheres to other material and tends to stretch somewhat and pull apart rather than to pull free from other material.
  • Hard.—When dry, moderately resistant to pressure; can be broken with difficulty between thumb and forefinger.
  • Soft.—When dry, breaks into powder or individual grains under very slight pressure.
  • Cemented.—Hard; little affected by moistening.
Control section.
The part of the soil on which classification is based. The thickness varies among different kinds of soil, but for many it is that part of the soil profile between depths of 10 inches and 40 or 80 inches.
Coprogenous earth (sedimentary peat).
Fecal material deposited in water by aquatic organisms.
Cover crop.
A close-growing crop grown primarily to improve and protect the soil between periods of regular crop production, or a crop grown between trees and vines in orchards and vineyards.
Cutbanks cave (in tables).
The walls of excavations tend to cave in or slough.
Depth to rock (in tables).
Bedrock is too near the surface for the specified use.
Drainage class (natural).
Refers to the frequency and duration of periods of saturation or partial saturation during soil formation, as opposed to altered drainage, which is commonly the result of artificial drainage or irrigation but may be caused by the sudden deepening of channels or the blocking of drainage outlets. Seven classes of natural soil drainage are recognized:
  • Excessively drained.—Water is removed from the soil very rapidly. Excessively drained soils are commonly very coarse textured, rocky, or shallow. Some are steep. All are free of the mottling related to wetness.
  • Somewhat excessively drained.—Water is removed from the soil rapidly. Many somewhat excessively drained soils are sandy and rapidly pervious. Some are shallow. Some are so steep that much of the water they receive is lost as runoff. All are free of the mottling related to wetness.
  • Well drained.—Water is removed from the soil readily, but not rapidly. It is available to plants throughout most of the growing season, and wetness does not inhibit growth of roots for significant periods during most growing seasons. Well drained soils are commonly medium textured. They are mainly free of mottling.
  • Moderately well drained.—Water is removed from the soil somewhat slowly during some periods. Moderately well drained soils are wet for only a short time during the growing season, but periodically they are wet long enough that most mesophytic crops are affected. They commonly have a slowly pervious layer within or directly below the solum or periodically receive high rainfall, or both.
  • Somewhat poorly drained.—Water is removed slowly enough that the soil is wet for significant periods during the growing season. Wetness markedly restricts the growth of mesophytic crops unless artificial drainage is provided. Somewhat poorly drained soils commonly have a slowly pervious layer, a high water table, additional water from seepage, nearly continuous rainfall, or a combination of these.
  • Poorly drained.—Water is removed so slowly that the soil is saturated periodically during the growing season or remains wet for long periods. Free water is commonly at or near the surface for long enough during the growing season that most mesophytic crops cannot be grown unless the soil is artificially drained. The soil is not continuously saturated in layers directly below plow depth. Poor drainage results from a high water table, a slowly pervious layer within the profile, seepage, nearly continuous rainfall, or a combination of these.
  • Very poorly drained.—Water is removed from the soil so slowly that free water remains at or on the surface during most of the growing season. Unless the soil is artificially drained, most mesophytic crops cannot be grown. Very poorly drained soils are commonly level or depressed and are frequently ponded. Yet, where rainfall is high and nearly continuous, they can have moderate or high slope gradients.
Drainage, surface.
Runoff, or surface flow of water, from an area.
Ecological plant communities.
The ecological plant communities in this survey area are as follows:
  • Everglades Flatwoods.—This community is in nearly level areas only in the Everglades region of south Florida. South Florida slash pine is the dominant tree species. Marlberry, saw palmetto, waxmyrtle, chalky bluestem, and creeping bluestem also grow in these areas.
  • Freshwater Marsh.—This community occurs as an open expanse of grasses, sedges, rushes, and other herbaceous plants. The dominant vegetation is sawgrass, cattail, cordgrass, and buttonbush. The water table is at or above the surface for 2 or more months during the year.
  • Mangrove Swamp.—This community is on saltwater shorelines south of Pasco County on the gulf coast and south of Volusia County on the Atlantic coast. The Ten Thousand Islands area of Monroe and Collier Counties is the largest area of this community in Florida and perhaps in the world. The community is in areas of very poorly drained, organic and marly, level soils that support a mangrove monoculture. The community is dominated by hydric soils.
  • Sand Pine Scrub.—This community is throughout Florida. It is most common inland from the coast and in the central part of the State. The largest areas are in the Ocala National Forest, in and around Marion County. The community is in areas of very droughty, rolling soils that support even-height stands of sand pine or dense stands of scrub oak. These areas do not have hydric soils.
  • Sawgrass Marsh.—This community is in the Everglades. It occurs as an open expanse of sawgrass in areas where the soil is saturated or covered with water during part of the year. Sawgrass, gulf muhly, plumegrass, and pickerelweed are the dominant plants.
  • Slough.—This community is throughout peninsular Florida. The largest areas are in Charlotte, Lee, and Collier Counties. The community occurs as nearly open areas of grasses, sedges, and rushes and scattered pine. The percentage of woody cover increases from the northern part of Florida to the southern part. This community is in areas of poorly drained, level soils that are covered with a few inches of slowly moving water during wet periods and do not support shrubs. Some areas in the northern part of Florida are dominated by trees. The community is dominated by hydric soils.
  • South Florida Coastal Strand.—This community is on nearly level to sloping soils adjacent to the Atlantic Ocean. The dominant vegetation is saw palmetto, seagrape, and seaoats.
  • Tropical Hammocks.—This community is interspersed throughout the Everglades Flatwoods community. Jamaica dogwood, mastic, poisontree, strangler fig, live oak, cabbage-palm, and wild coffee are the most common plants.
Effervescence.
As used in this survey, the bubbling of carbon dioxide when dilute hydrochloric acid is applied to calcium carbonates.
Eluviation.
The movement of material in true solution or colloidal suspension from one place to another within the soil. Soil horizons that have lost material through eluviation are eluvial; those that have received material are illuvial.
Eolian soil material.
Earthy parent material accumulated through wind action; commonly refers to sandy material in dunes or to loess in blankets on the surface.
Erosion.
The wearing away of the land surface by water, wind, ice, or other geologic agents and by such processes as gravitational creep.
  • Erosion (geologic) .—Erosion caused by geologic processes acting over long geologic periods and resulting in the wearing away of mountains and the building up of such landscape features as flood plains and coastal plains. Synonym: natural erosion.
  • Erosion (accelerated) .—Erosion much more rapid than geologic erosion, mainly as a result of human or animal activities or of a catastrophe in nature, such as fire, that exposes the surface.
Erosion pavement.
A layer of gravel or stones that remains on the surface after fine particles are removed by sheet or rill erosion.
Excess fines (in tables).
Excess silt and clay in the soil. The soil is not a source of gravel or sand for construction purposes.
Excess salt (in tables).
Excess water-soluble salts in the soil that restrict the growth of most plants.
Fallow.
Cropland left idle in order to restore productivity through accumulation of moisture. Summer fallow is common in regions of limited rainfall where cereal grains are grown. The soil is tilled for at least one growing season for weed control and decomposition of plant residue.
Fast intake (in tables).
The movement of water into the soil is rapid.
Fertility, soil.
The quality that enables a soil to provide plant nutrients, in adequate amounts and in proper balance, for the growth of specified plants when light, moisture, temperature, tilth, and other growth factors are favorable.
Fibric soil material (peat).
The least decomposed of all organic soil material. Peat contains a large amount of well preserved fiber that is readily identifiable according to botanical origin. Peat has the lowest bulk density and the highest water content at saturation of all organic soil material.
Field moisture capacity.
The moisture content of a soil, expressed as a percentage of the ovendry weight, after the gravitational, or free, water has drained away; the field moisture content 2 or 3 days after a soaking rain; also called normal field capacity, normal moisture capacity, or capillary capacity.
Fill.
Material used to raise the surface of the land to a desired level.
Fine textured soil.
Sandy clay, silty clay, or clay.
Flagstone.
A thin fragment of sandstone, limestone, slate, shale, or (rarely) schist, 6 to 15 inches (15 to 37.5 centimeters) long.
Flatwoods.
Broad, nearly level, low ridges characterized by an open pine forest and an understory of saw palmetto and pineland threeawn and by poorly drained soils that are dominantly sandy.
Flood plain.
A nearly level alluvial plain that borders a stream and is subject to flooding unless protected artificially.
Forb.
Any herbaceous plant that is not a grass or a sedge.
Genesis, soil.
The mode of origin of the soil. Refers especially to the processes or soil-forming factors responsible for the formation of the solum, or true soil, from the unconsolidated parent material.
Gleyed soil.
Soil that formed under poor drainage, resulting in the reduction of iron and other elements in the profile and in gray colors and mottles.
Gravel.
Rounded or angular fragments of rock up to 3 inches (2 millimeters to 7.6 centimeters) in diameter. An individual piece is a pebble.
Gravelly soil material.
Material that is 15 to 50 percent, by volume, rounded or angular rock fragments, not prominently flattened, up to 3 inches (7.6 centimeters) in diameter.
Green manure crop (agronomy).
A soil-improving crop grown to be plowed under in an early stage of maturity or soon after maturity.
Ground water (geology).
Water filling all the unblocked pores of the material below the water table.
Hammock.
A densely wooded area that is slightly elevated above the adjacent areas and has characteristic natural vegetation of cabbage-palm, oak, and pine and an understory of saw palmetto, shrubs, and grasses.
Hardpan.
A hardened or cemented soil horizon, or layer. The soil material is sandy, loamy, or clayey and is cemented by iron oxide, silica, calcium carbonate, or other substance.
Hemic soil material (mucky peat).
Organic soil material intermediate in degree of decomposition between the less decomposed fibric and the more decomposed sapric material.
Horizon, soil.
A layer of soil, approximately parallel to the surface, having distinct characteristics produced by soil-forming processes. In the identification of soil horizons, an uppercase letter represents the major horizons. Numbers or lowercase letters that follow represent subdivisions of the major horizons. An explanation of the subdivisions is given in the "Soil Survey Manual." The major horizons of mineral soil are as follows:
  • O horizon.—An organic layer of fresh and decaying plant residue at the surface of a mineral soil.
  • A horizon.—The mineral horizon at or near the surface in which an accumulation of humified organic matter is mixed with the mineral material. Also, a plowed surface horizon, most of which was originally part of a B horizon.
  • E horizon.—The mineral horizon in which the main feature is loss of silicate clay, iron, aluminum, or some combination of these.
  • B horizon.—The mineral horizon below an O, A, or E horizon. The B horizon is, in part, a layer of transition from the overlying horizon to the underlying C horizon. The B horizon also has distinctive characteristics, such as accumulation of clay, sesquioxides, humus, or a combination of these; prismatic or blocky structure; redder or browner colors than those in the A horizon; or a combination of these. The combined A and B horizons are generally called the solum, or true soil. If a soil does not have a B horizon, the A horizon alone is the solum.
  • C horizon.—The mineral horizon or layer, excluding indurated bedrock, that is little affected by soil-forming processes and does not have the properties typical of the A or B horizon. The material of a C horizon may be either like or unlike that in which the solum formed. If the material is known to differ from that in the solum, the Arabic numeral 2 precedes the letter C.
  • Cr horizon.—Soft, consolidated bedrock beneath the soil.
  • R layer.—Consolidated rock (unweathered bedrock) beneath the soil. The bedrock commonly underlies a C horizon but can be directly below an A or a B horizon.
Humus.
The well decomposed, more or less stable part of the organic matter in mineral soils.
Hydrologic soil groups.
Refers to soils grouped according to their runoff-producing characteristics. The chief consideration is the inherent capacity of soil bare of vegetation to permit infiltration. The slope and the kind of plant cover are not considered but are separate factors in predicting runoff. Soils are assigned to four groups. In group A are soils having a high infiltration rate when thoroughly wet and having a low runoff potential. They are mainly deep, well drained, and sandy or gravelly. In group D, at the other extreme, are soils having a very slow infiltration rate and thus a high runoff potential. They have a claypan or clay layer at or near the surface, have a permanent high water table, or are shallow over nearly impervious bedrock or other material. A soil is assigned to two hydrologic groups if part of the acreage is artificially drained and part is undrained.
Illuviation.
The movement of soil material from one horizon to another in the soil profile. Generally, material is removed from an upper horizon and deposited in a lower horizon.
Impervious soil.
A soil through which water, air, or roots penetrate slowly or not at all. No soil is absolutely impervious to air and water all the time.
Infiltration.
The downward entry of water into the immediate surface of soil or other material. This contrasts with percolation, which is movement of water through soil layers or material.
Infiltration capacity.
The maximum rate at which water can infiltrate into a soil under a given set of conditions.
Infiltration rate.
The rate at which water penetrates the surface of the soil at any given instant, usually expressed in inches per hour. The rate can be limited by the infiltration capacity of the soil or the rate at which water is applied at the surface.
Intake rate.
The average rate of water entering the soil under irrigation. Most soils have a fast initial rate; the rate decreases with application time. Therefore, intake rate for design purposes is not a constant but is a variable depending on the net irrigation application. The rate of water intake, in inches per hour, is expressed as follows: 
Less than 0.2.....very low 
0.2 to 0.4........low 
0.4 to 0.75.......moderately low 
0.75 to 1.25......moderate 
1.25 to 1.75......moderately high 
1.75 to 2.5.......high 
More than 2.5.....very high
Irrigation.
Application of water to soils to assist in production of crops. Methods of irrigation are:
  • Basin.—Water is applied rapidly to nearly level plains surrounded by levees or dikes.
  • Border.—Water is applied at the upper end of a strip in which the lateral flow of water is controlled by small earth ridges called border dikes, or borders.
  • Controlled flooding.—Water is released at intervals from closely spaced field ditches and distributed uniformly over the field.
  • Corrugation.—Water is applied to small, closely spaced furrows or ditches in fields of close-growing crops or in orchards so that it flows in only one direction.
  • Drip (or trickle).—Water is applied slowly and under low pressure to the surface of the soil or into the soil through such applicators as emitters, porous tubing, or perforated pipe.
  • Furrow.—Water is applied in small ditches made by cultivation implements. Furrows are used for tree and row crops.
  • Sprinkler.—Water is sprayed over the soil surface through pipes or nozzles from a pressure system.
  • Subirrigation.—Water is applied in open ditches or tile lines until the water table is raised enough to wet the soil.
  • Wild flooding.—Water, released at high points, is allowed to flow onto an area without controlled distribution.
Karst (topography).
The relief of an area underlain by limestone that dissolves in differing degrees, thus forming numerous depressions or small basins.
Land leveling.
Cutting and filling so that the suitability of a site for an intended is improved.
Leaching.
The removal of soluble material from soil or other material by percolating water.
Liquid limit.
The moisture content at which the soil passes from a plastic to a liquid state.
Loam.
Soil material that is 7 to 27 percent clay particles, 28 to 50 percent silt particles, and less than 52 percent sand particles.
Low strength.
The soil is not strong enough to support loads.
Marl.
An unconsolidated mineral deposited in marine or fresh water and consisting chiefly of silt- and clay-sized particles of calcium carbonate.
Medium textured soil.
Very fine sandy loam, loam, silt loam, or silt.
Mineral soil.
Soil that is mainly mineral material and low in organic material. Its bulk density is more than that of organic soil.
Minimum tillage.
Only the tillage essential to crop production and prevention of soil damage.
Miscellaneous area.
An area that has little or no natural soil and supports little or no vegetation.
Moderately coarse textured soil.
Coarse sandy loam, sandy loam, or fine sandy loam.
Moderately fine textured soil.
Clay loam, sandy clay loam, or silty clay loam.
Morphology, soil.
The physical makeup of the soil, including the texture, structure, porosity, consistence, color, and other physical, mineral, and biological properties of the various horizons, and the thickness and arrangement of those horizons in the soil profile.
Mottling, soil.
Irregular spots of different colors that vary in number and size. Mottling generally indicates poor aeration and impeded drainage. Descriptive terms are as follows: abundance—few, common, and many; size—fine, medium, and coarse; and contrast—faint, distinct, and prominent. The size measurements are of the diameter along the greatest dimension. Fine indicates less than 5 millimeters (about 0.2 inch); medium, from 5 to 15 millimeters (about 0.2 to 0.6 inch); and coarse, more than 15 millimeters (about 0.6 inch).
Mounding.
On sites for septic tank absorption fields, filling with suitable soil material to the level above the water table needed to meet local and State requirements.
Muck.
Dark, finely divided, well decomposed organic soil material. (See Sapric soil material.)
Munsell notation.
A designation of color by degrees of three simple variables—hue, value, and chroma. For example, a notation of 10YR 6/4 is a color with hue of 10YR, value of 6, and chroma of 4.
Neutral soil.
A soil having a pH value between 6.6 and 7.3. (See Reaction, soil.)
Nutrient, plant.
Any element taken in by a plant essential to its growth. Plant nutrients are mainly nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, boron, and zinc obtained from the soil and carbon, hydrogen, and oxygen obtained from the air and water.
Organic matter.
Plant and animal residue in the soil in various stages of decomposition.
Pan.
A compact, dense layer in a soil that impedes the movement of water and the growth of roots. For example, hardpan, fragipan, claypan, plowpan, and traffic pan.
Parent material.
The unconsolidated organic and mineral material in which soil forms.
Peat.
Unconsolidated material, largely undecomposed organic matter, that has accumulated under excess moisture. (See Fibric soil material.)
Ped.
An individual natural soil aggregate, such as a granule, a prism, or a block.
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.
Permeability.
The quality of the soil that enables water to move through the profile. Permeability is measured as the number of inches per hour that water moves through the saturated soil. Terms describing permeability are: 
Very slow............less than 0.06 inch 
Slow.................0.06 to 0.2 inch 
Moderately slow......0.2 to 0.6 inch 
Moderate.............0.6 inch to 2.0 inches 
Moderately rapid.....2.0 to 6.0 inches 
Rapid................6.0 to 20 inches 
Very rapid...........more than 20 inches
Phase, soil.
A subdivision of a soil series based on features that affect its use and management. For example, slope, stoniness, and thickness.
pH value.
A numerical designation of acidity and alkalinity in soil. (See Reaction, soil.)
Piping (in tables).
Subsurface tunnels or pipelike cavities are formed by water moving through the soil.
Plasticity index.
The numerical difference between the liquid limit and the plastic limit; the range of moisture content within which the soil remains plastic.
Plastic limit.
The moisture content at which a soil changes from semisolid to plastic.
Plowpan.
A compacted layer formed in the soil directly below the plowed layer.
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 (in tables).
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.
Poor outlets (in tables).
Refers to areas where surface or subsurface drainage outlets are difficult or expensive to install.
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.
Reaction, soil.
A measure of the acidity or alkalinity of a soil expressed in pH values. A soil that tests to pH 7.0 is described as precisely neutral in reaction because it is neither acid nor alkaline. The degrees of acidity or alkalinity, expressed as pH values, are: 
Extremely acid................below 4.5 
Very strongly acid...........4.5 to 5.0 
Strongly acid................5.1 to 5.5 
Moderately acid..............5.6 to 6.0 
Slightly acid................6.1 to 6.5 
Neutral......................6.6 to 7.3 
Mildly alkaline..............7.4 to 7.8 
Moderately alkaline..........7.9 to 8.4 
Strongly alkaline............8.5 to 9.0 
Very strongly alkaline.......9.1 and higher
Regolith.
The unconsolidated mantle of weathered rock and soil material on the earth's surface; the loose earth material above the solid rock.
Relief.
The elevations or inequalities of a land surface, considered collectively.
Residuum (residual soil material).
Unconsolidated, weathered or partly weathered mineral material that accumulated as consolidated rock disintegrated in place.
Rippable.
Rippable bedrock or hardpan can be excavated using a single-tooth ripping attachment mounted on a tractor with a 200-300 drawbar horsepower rating.
Rock fragments.
Rock or mineral fragments having a diameter of 2 millimeters or more; for example, pebbles, cobbles, stones, and boulders.
Root zone.
The part of the soil that can be penetrated by plant roots.
Runoff.
The precipitation discharged into stream channels from an area. The water that flows off the surface of the land without sinking into the soil is called surface runoff. Water that enters the soil before reaching surface streams is called ground-water runoff or seepage flow from ground water.
Saline soil.
A soil containing soluble salts in an amount that impairs the growth of plants. A saline soil does not contain excess exchangeable sodium.
Salty water (in tables).
Water is too salty for consumption by livestock.
Sand.
As a soil separate, individual rock or mineral fragments from 0.05 millimeter to 2.0 millimeters in diameter. Most sand grains consist of quartz. As a soil textural class, a soil that is 85 percent or more sand and not more than 10 percent clay.
Sapric soil material (muck).
The most highly decomposed of all organic soil material. Muck has the least amount of plant fiber, the highest bulk density, and the lowest water content at saturation of all organic soil material.
Saprolite (soil science).
Unconsolidated, residual material underlying the soil and grading to hard bedrock below.
Sedimentary rock.
Rock made up of particles deposited from suspension in water. The chief kinds of sedimentary rock are conglomerate, formed from gravel; sandstone, formed from sand; shale, formed from clay; and limestone, formed from soft masses of calcium carbonate. There are many intermediate types. Some wind-deposited sand is consolidated into sandstone.
Seepage (in tables).
The movement of water through the soil adversely affects the specified use.
Sequum.
A sequence consisting of an illuvial horizon and the overlying eluvial horizon. (See Eluviation.)
Series, soil.
A group of soils that have profiles that are almost alike, except for differences in texture of the surface layer or of the underlying material. All the soils of a series have horizons that are similar in composition, thickness, and arrangement.
Silica.
A combination of silicon and oxygen. The mineral form is called quartz.
Silica-sesquioxide ratio.
The ratio of the number of molecules of silica to the number of molecules of alumina and iron oxide. The more highly weathered soils or their clay fractions in warm-temperate, humid regions, and especially those in the tropics, generally have a low ratio.
Silt.
As a soil separate, individual mineral particles that range in diameter from the upper limit of clay (0.002 millimeter) to the lower limit of very fine sand (0.05 millimeter). As a soil textural class, soil that is 80 percent or more silt and less than 12 percent clay.
Sinkhole.
A depression in the landscape where limestone has been dissolved.
Slope.
The inclination of the land surface from the horizontal. Percentage of slope is the vertical distance divided by horizontal distance, then multiplied by 100. Thus, a slope of 20 percent is a drop of 20 feet in 100 feet of horizontal distance.
Slow refill (in tables).
The slow filling of ponds, resulting from restricted permeability in the soil.
Small stones (in tables).
Rock fragments less than 3 inches (7.6 centimeters) in diameter. Small stones adversely affect the specified use of the soil.
Sodicity.
The degree to which a soil is affected by exchangeable sodium. Sodicity is expressed as a sodium adsorption ratio (SAR) of a saturation extract, or the ratio of Na+ to Ca++ + Mg++. The degrees of sodicity and their respective ratios are: 
Slight.........less than 13:1 
Moderate.......13-30:1 
Strong.........more than 30:1
Soil.
A natural, three-dimensional body at the earth's surface. It is capable of supporting plants and has properties resulting from the integrated effect of climate and living matter acting on earthy parent material, as conditioned by relief over periods of time.
Soil separates.
Mineral particles less than 2 millimeters in equivalent diameter and ranging between specified size limits. The names and sizes, in millimeters, of separates recognized in the United States are as follows: 
Very coarse sand.......2.0 to 1.0 
Coarse sand............1.0 to 0.5 
Medium sand............0.5 to 0.25 
Fine sand..............0.25 to 0.10 
Very fine sand.........0.10 to 0.05 
Silt...................0.05 to 0.002 
Clay...................less than 0.002
Solum.
The upper part of a soil profile, above the C horizon, in which the processes of soil formation are active. The solum in soil consists of the A, E, and B horizons. Generally, the characteristics of the material in these horizons are unlike those of the underlying material. The living roots and plant and animal activities are largely confined to the solum.
Stone line.
A concentration of coarse fragments in a soil. Generally, it is indicative of an old weathered surface. In a cross section, thickness of the line can be one fragment or more. It generally overlies material that weathered in place, and it is overlain by recent sediment of variable thickness.
Stones.
Rock fragments 10 to 24 inches (25 to 60 centimeters) in diameter if rounded or 15 to 24 inches (38 to 60 centimeters) in length if flat.
Stony.
Refers to a soil containing stones in numbers that interfere with or prevent tillage.
Stripcropping.
Growing crops in a systematic arrangement of strips or bands that provide vegetative barriers to soil blowing and water erosion.
Structure, soil.
The arrangement of primary soil particles into compound particles or aggregates. The principal forms of soil structure are—platy (laminated), prismatic (vertical axis of aggregates longer than horizontal), columnar (prisms with rounded tops), blocky (angular or subangular), and granular. Structureless soils are either single grained (each grain by itself, as in dune sand) or massive (the particles adhering without any regular cleavage, as in many hardpans).
Stubble mulch.
Stubble or other crop residue left on the soil or partly worked into the soil. It protects the soil from soil blowing and water erosion after harvest, during preparation of a seedbed for the next crop, and during the early growing period of the new crop.
Subsoil.
Technically, the B horizon; roughly, the part of the solum below plow depth.
Subsoiling.
Breaking up a compact subsoil by pulling a special chisel through the soil.
Substratum.
The part of the soil below the solum.
Subsurface layer.
Technically, the E horizon. Generally refers to a leached horizon lighter in color and lower in organic matter content than the overlying surface layer.
Summer fallow.
The tillage of uncropped land during the summer to control weeds and allow storage of moisture in the soil for the growth of a later crop. A practice common in semiarid regions, where annual precipitation is not enough to produce a crop every year. Summer fallow is frequently practiced before planting winter grain.
Surface layer.
The soil ordinarily moved in tillage, or its equivalent in uncultivated soil, ranging in depth from 4 to 10 inches (10 to 25 centimeters). Frequently designated as the "plow layer," or the "Ap horizon."
Terrace (geologic).
An old alluvial plain, ordinarily flat or undulating, bordering a river, a lake, or the sea.
Texture, soil.
The relative proportions of sand, silt, and clay particles in a mass of soil. The basic textural classes, in order of increasing proportion of fine particles, are sand, loamy sand, sandy loam, loam, silt loam, silt, sandy clay loam, clay loam, silty clay loam, sandy clay, silty clay, and clay. The sand, loamy sand, and sandy loam classes may be further divided by specifying "coarse," "fine," or "very fine."
Thin layer (in tables).
An otherwise suitable soil material that is too thin for the specified use.
Tilth, soil.
The physical condition of the soil as related to tillage, seedbed preparation, seedling emergence, and root penetration.
Topsoil.
The upper part of the soil, which is the most favorable material for plant growth. It is ordinarily rich in organic matter and is used to topdress roadbanks, lawns, and land affected by mining.
Trace elements.
Chemical elements, such as zinc, cobalt, manganese, copper, and iron, in soils in extremely small amounts. They are essential to plant growth.
Upland (geology).
Land at a higher elevation, in general, than the alluvial plain or stream terrace; land above the lowlands along streams.
Variegation.
Refers to patterns of contrasting colors that are assumed to be inherited from the parent material rather than to be the result of poor drainage.
Weathering.
All physical and chemical changes produced by atmospheric agents in rocks or other deposits at or near the earth's surface. These changes result in disintegration and decomposition of the material.
Well graded.
Refers to soil material consisting of coarse grained particles that are well distributed over a wide range in size or diameter. Such soil normally can be easily increased in density and bearing properties by compaction. Contrasts with poorly graded soil.
Wilting point (or permanent wilting point).
The moisture content of soil, on an ovendry basis, at which a plant (specifically a sunflower) wilts so much that it does not recover when placed in a humid, dark chamber.

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