This is an index of articles relating to

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

. {{Compact ToC , side = yes , num = yes , seealso = yes , nobreak = yes , extlinks = no , center = yes

A

Acid sulfate soil Acid sulfate soils are naturally occurring soils, sediments or organic substrates (e.g. peat) that are formed under waterlogged conditions. These soils contain iron sulfide minerals (predominantly as the mineral pyrite) and/or their oxidation produ ...

- Acrisol - Active layer -

Agricultural soil science Agricultural soil science is a branch of soil science that deals with the study of edaphic conditions as they relate to the production of food and fiber. In this context, it is also a constituent of the field of agronomy and is thus also descr ...

- Akadama -

Albeluvisols Albeluvisol was a Reference Soil Group of the first edition (1998) and the second edition (2006) of the World Reference Base for Soil Resources (WRB). In the third edition of the WRB (2014), Albeluvisols were replaced by the broader defined Retis ...

Alfisols Alfisols are a soil order in USDA soil taxonomy. Alfisols form in semi-arid to humid areas, typically under a hardwood forest cover. They have a clay-enriched subsoil and relatively high native fertility. "Alf" refers to aluminium (Al) and iron ( ...

- Alkali soil -

Andisols In USDA soil taxonomy, Andisols are soils formed in volcanic ash and defined as soils containing high proportions of glass and amorphous colloidal materials, including allophane, imogolite and ferrihydrite. In the World Reference Base for Soil Re ...

Angle of repose The angle of repose, or critical angle of repose, of a granular material is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope fac ...

Antigo (soil) Antigo soils are among the most extensive soils in Wisconsin. They occur on about 300,000 acres (1,200 km²) in the northern part of the State. Antigo soils are well-drained and formed under northern hardwood forests in loess and loamy sedim ...

Anthrosol An anthrosol (or anthropogenic soil) in the World Reference Base for Soil Resources (WRB) is a type of soil that has been formed or heavily modified due to long-term human activity, such as from irrigation, addition of organic waste or wet-field cul ...

Aridisols Arid soils (or desert soils) are a soil order in USDA soil taxonomy. Aridisols (from the Latin ''aridus'', for "dry", and ''solum'') form in an arid or semi-arid climate. Aridisols dominate the deserts and xeric shrublands, which occupy about one ...

Atriplex ''Atriplex'' () is a plant genus of about 250 species, known by the common names of saltbush and orache (; also spelled orach). It belongs to the subfamily Chenopodioideae of the family Amaranthaceae ''s.l.''. The genus is quite variable and w ...

Australian Society of Soil Science Incorporated The Australian Society of Soil Science Incorporated (ASSSI) was founded in 1955 to "advance soil science in the professional, academic, and technical fields". The Society consists of a federation of branches operating the 'umbrella' of the ASSSI Fe ...

B

Baer's law - Bama (soil) -

Barren vegetation Barren vegetation describes an area of land where plant growth may be sparse, stunted, and/or contain limited biodiversity. Environmental conditions such as toxic or infertile soil, high winds, coastal salt-spray, and climatic conditions are of ...

Base-richness In ecology, base-richness is the level of Base (chemistry), chemical bases in water or soil, such as calcium or magnesium ions. Many organisms prefer base-rich environments. Chemical bases are alkalis, hence base-rich environments are either pH, ...

Bay mud Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuaries, which are normally in temperate regions that have experienced cyclical glacia ...

Bearing capacity In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce she ...

- Bentonite -

Berkshire (soil) Berkshire soil series is the name given to a well-drained loam or sandy loam soil which has developed on glacial till in parts of southern Quebec, eastern New York State and New England south to Massachusetts. It belongs to the podzol soil group a ...

Bevameter A bevameter is a device used in terramechanics to measure the mechanical properties of soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life ...

- Biochar -

Biogeology Biogeology is the study of the interactions between the Earth's biosphere and the lithosphere. Biogeology examines biotic, hydrologic, and terrestrial systems in relation to each other, to help understand the Earth's climate, oceans, and other e ...

Blandford (soil) Blandford soil series is the name given to a loam or sandy loam soil which has developed on glacial till in parts of southern Quebec and northern New England. It belongs to the brown podzolic soil group and occurs in hilly areas of the Green Mounta ...

Blue goo Blue goo is a sticky, plasticky, blueish-grey, clay-textured soil derived from a highly weathered serpentinite mélange. The name derives from the soil's color; a result of undergoing anaerobic conditions and becoming gleyed. A greyer variation i ...

Bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...

- Brickearth - Brown earth -

Brown podzolic Brown podzolic soils are a subdivision of the Podzolic soils in the British soil classification. Although classed with podzols because they have an iron-rich, or spodic horizon, they are, in fact intermediate between podzols and Brown earths. Th ...

C

Calcareous grassland -

Calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

- Calciorthid -

Calcisols A Calcisol in the World Reference Base for Soil Resources (WRB) is a soil with a substantial secondary accumulation of lime. Calcisols are common in calcareous parent materials and widespread in arid and semi-arid environments. Formerly Calcisols w ...

Cambisols A Cambisol in the World Reference Base for Soil Resources (WRB) is a soil in the beginning of soil formation. The horizon differentiation is weak. This is evident from weak, mostly brownish discolouration and/or structure formation in the soil pro ...

Canada Land Inventory The Canada Land Inventory (CLI) is a multi-disciplinary land inventory of rural Canada. Conceptualized in the early 1960s by the Department of Forestry and Rural Development (later the Department of Energy, Mines and Resources), the CLI was a fed ...

Capacitance probe Capacitance sensors (or Dielectric sensors) use capacitance to measure the dielectric permittivity of a surrounding medium. The configuration is like the neutron probe where an access tube made of PVC is installed in the soil; probes can also be mo ...

Carbon cycle re-balancing Climate change mitigation is action to limit climate change by reducing emissions of greenhouse gases or removing those gases from the atmosphere. The recent rise in global average temperature is mostly caused by emissions from fossil fuels bur ...

- Casa Grande (soil) - Cation-exchange capacity - Cellular confinement - Cecil (soil) -

Characterisation of pore space in soil The pore space of soil contains the liquid and gas phases of soil, i.e., everything but the solid phase that contains mainly minerals of varying sizes as well as organic compounds. In order to understand porosity better a series of equations have b ...

Charlottetown (soil series) Charlottetown soil series is the name given to a deep fine sandy loam soil which has developed under forest vegetation on glacial till. This series occurs only on Prince Edward Island, where it is widespread and so important for agriculture that it ...

- Chernozem -

Clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

- Claypan - Cob (material) -

Cohesion (geology) Cohesion is the component of Shear strength (soil), shear strength of a Rock (geology), rock or soil that is independent of interparticle friction. In soils, true cohesion is caused by following: # Electrostatic forces in stiff consolidation (soil) ...

- Compressed earth block - Consolidation (soil) -

Contour ploughing Contour bunding or contour farming or Contour ploughing is the farming practice of plowing and/or planting across a slope following its elevation contour lines. These contour lines create a water break which reduces the formation of rills and gu ...

- Critical state soil mechanics

D

Darcy (unit) The darcy (or darcy unit) and millidarcy (md or mD) are units of permeability, named after Henry Darcy. They are not SI units, but they are widely used in petroleum engineering and geology. The unit has also been used in biophysics and biomechani ...

- Darcy's law -

Darcy–Weisbach equation In fluid dynamics, the Darcy–Weisbach equation is an empirical equation that relates the head loss, or pressure loss, due to friction along a given length of pipe to the average velocity of the fluid flow for an incompressible fluid. The equation ...

- Dark earth -

Dispersion (geology) Dispersion is a process that occurs in soils that are particularly vulnerable to erosion by water. In soil layers where clays are saturated with sodium ions ("sodic soils"), soil can break down very easily into fine particles and wash away. This ca ...

Downer (soil) Downer is the New Jersey state soil. The Downer has four soil horizons: *Surface layer: dark grayish brown loamy sand *Subsurface layer: grayish brown sandy loam *Subsoil - upper: yellowish brown gravelly sandy loam *Subsoil - lower: yellowish bro ...

- Downhill creep -

Drainage research Drainage research is the study of agricultural drainage systems and their effects to arrive at optimal system design. Aspects to be covered Agricultural land drainage has agricultural, environmental, hydrological, engineering, economical, socia ...

- Drilosphere - Drucker–Prager yield criterion - Drummer (soil) -

Dry quicksand Dry quicksand is loose sand whose bulk density is reduced by blowing air through it and which yields easily to weight or pressure. It acts similarly to normal quicksand, but it does not contain any water and does not operate on the same principle ...

Dryland salinity Dryland salinity is a natural process for soil, just like other processes such as wind erosion. Salinity degrades land by an increase in soil salt concentration in the environment, watercourse or soil in unirrigated landscapes, being in excess of ...

Duricrust Duricrust is a hard layer on or near the surface of soil. Duricrusts can range in thickness from a few millimeters or centimeters to several meters. It is a general term (not to be confused with duripan) for a zone of chemical precipitation and ...

- Durisols -

Dynamic compaction Dynamic compaction is a method that is used to increase the density of the soil when certain subsurface constraints make other methods inappropriate. It is a method that is used to increase the density of soil deposits. The process involves dropp ...

E

Ecological land classification Ecological classification or ecological typology is the classification of land or water into geographical units that represent variation in one or more ecological features. Traditional approaches focus on geology, topography, biogeography, soils, ve ...

Ecosystem ecology Ecosystem ecology is the integrated study of living ( biotic) and non-living (abiotic) components of ecosystems and their interactions within an ecosystem framework. This science examines how ecosystems work and relates this to their components s ...

- Edaphic - Edaphology -

Effective stress The effective stress can be defined as the stress, depending on the applied tension \boldsymbol_ and pore pressure p, which controls the strain or strength behaviour of soil and rock (or a generic porous body) for whatever pore pressure value or, ...

- Eluvium -

Entisol Entisols are soils defined in USDA soil taxonomy that do not show any profile development other than an A horizon. An entisol has no diagnostic horizons, and most are basically unaltered from their parent material, which can be unconsolidated sedi ...

- Environmental impact of irrigation -

Erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

- European Soil Bureau Network - European Soil Database -

Expansive clay Expansive clay is a clay soil that is prone to large volume changes (swelling and shrinking) that are directly related to changes in water content. Soils with a high content of expansive minerals can form deep cracks in drier seasons or years; su ...

F

Factors affecting permeability of soils -

Fech fech Fech fech ( ar, فش فش) is a very fine powder caused by the erosion of clay-limestone terrain and it is most commonly found in deserts. It consists of a surface horizon of pulverized soil with low particle cohesion protected under a thin crust ...

Fen A fen is a type of peat-accumulating wetland fed by mineral-rich ground or surface water. It is one of the main types of wetlands along with marshes, swamps, and bogs. Bogs and fens, both peat-forming ecosystems, are also known as mires. T ...

Ferrallitisation Ferrallitisation is the process in which rock is changed into a soil consisting of clay ( kaolinite) and sesquioxides, in the form of hydrated oxides of iron and aluminium. In humid tropical areas, with consistently high temperatures and rainfall fo ...

- Fill dirt -

Flatwood Flatwood is a soil series with impaired drainage that occurs in the southeastern United States. Flatwood soils are upland soils formed from marine sediments. A shallow water table plays a role in soil formation; typically the water table is only a ...

Flownet A flow net is a graphical representation of two-dimensional steady-state groundwater flow through aquifers. Construction of a flow net is often used for solving groundwater flow problems where the geometry makes analytical solutions impractical. Th ...

Fractal in soil mechanics A fractal is an irregular geometric object with an infinite nesting of structure at all scales. It is mainly applicable in soil chromatography and soil micromorphology (Anderson, 1997). Internal structure, pore size distribution and pore geometry ...

- Frequency domain sensor - Fresno scraper - Frost heaving -

Frost line The frost line—also known as frost depth or freezing depth—is most commonly the depth to which the groundwater in soil is expected to freeze. The frost depth depends on the climatic conditions of an area, the heat transfer properties of the s ...

Fuller's earth Fuller's earth is any clay material that has the capability to decolorize oil or other liquids without the use of harsh chemical treatment. Fuller's earth typically consists of palygorskite (attapulgite) or bentonite. Modern uses of fuller's ea ...

G

Gelisols Gelisols are an order in USDA soil taxonomy. They are soils of very cold climates which are defined as containing permafrost within two meters of the soil surface. The word "Gelisol" comes from the Latin ''gelare'' meaning "to freeze", a referen ...

Geosmin Geosmin ( ) is an irregular sesquiterpenoid, produced from the universal sesquiterpene precursor farnesyl pyrophosphate (also known as farnesyl diphosphate), in a two-step -dependent reaction. Geosmin, along with the irregular monoterpene 2-met ...

- Geotechnical investigation -

Gleysol A gleysol is a wetland soil (hydric soil) that, unless drained, is saturated with groundwater for long enough to develop a characteristic colour pattern. The pattern is essentially made up of reddish, brownish, or yellowish colours at surfaces o ...

- Gravitational erosion - Groundwater-related subsidence - Guelph soil - Gypcrust - Gypsisols

H

Hardpan -

Headland (agriculture) A Headland, in agriculture, is the area at each end of a planted field. In some areas of the United States, this area is known as the Turnrow. It is used for turning around with farm implements during field operations and is the first area to be ...

- Hesco bastion - Hilo (soil) -

History of soil science The early concepts of soil were based on ideas developed by a German chemist, Justus von Liebig (1803–1873), and modified and refined by agricultural scientists who worked on samples of soil in laboratories, greenhouses, and on small field plots ...

Histosol In both the World Reference Base for Soil Resources (WRB) and the USDA soil taxonomy, a Histosol is a soil consisting primarily of organic materials. They are defined as having or more of organic soil material in the upper . Organic soil materia ...

Houdek (soil) Houdek is a type of soil composed of glacial till and decomposed organic matter. The soil series was established in 1955 in Spink County, South Dakota. It is unique to the United States, but in particular to South Dakota where it is the state so ...

Hume (soil) Hume is a soil type that is well drained and slowly permeable. Hume is formed from the erosion of shale and sandstone. Hume soils occur naturally on slopes and alluvial fan An alluvial fan is an accumulation of sediments that fans outwards fr ...

Humin Humins are carbon-based macromolecular substances, that can be found in soil chemistry or as a by-product from saccharide-based biorefinery processes. Humins in soil chemistry Soil consists of both mineral (inorganic) and organic components. The ...

Humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

Hydraulic conductivity Hydraulic conductivity, symbolically represented as (unit: m/s), is a property of porous materials, soils and rocks, that describes the ease with which a fluid (usually water) can move through the pore space, or fractures network. It depends on th ...

- Hydric soil - Hydro axe mulching - Hydrological transport model -

Hydropedology Hydropedology is an emerging field formed from the intertwining branches of soil science and hydrology. Similar to hydrogeology, hydroclimatology, and ecohydrology, the emphasis is connections between hydrology and other of the earth's spheres. ...

Hydrophobic soil Hydrophobic soil is a soil whose particles repel water. The layer of hydrophobicity is commonly found at or a few centimeters below the surface, parallel to the soil profile. This layer can vary in thickness and abundance and is typically covered ...

I

Immobilization (soil science) Immobilization in soil science is the conversion of inorganic compounds to organic compounds by micro-organisms or plants by which the compounds become inaccessible to plants. Immobilization is the opposite of mineralization. In immobilization, i ...

Inceptisols Inceptisols are a soil order in USDA soil taxonomy. They form quickly through alteration of parent material. They are more developed than Entisols. They have no accumulation of clays, iron oxide, aluminium oxide or organic matter. They have an o ...

- Infiltration capacity - International Humic Substances Society -

International Soil Reference and Information Centre ISRIC - World Soil Information, legally known as International Soil Reference and Information Centre, is an independent science-based foundation. The institute was founded in 1966 following a recommendation of the International Society of Soil Scie ...

- International Union of Soil Sciences

J

Jory (soil) The Jory series consists of very deep, well-drained soils that formed in colluvium derived from basic igneous rock. These soils are in the foothills surrounding the Willamette Valley of the United States. They have been mapped on more than in west ...

K

Kalkaska sand - Kerogen

L

Lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extreme ...

Laimosphere The laimosphere is the microbiologically enriched zone of soil that surrounds below-ground portions of plant stems; the laimosphere is analogous to the rhizosphere and spermosphere. The combining form laim- from (Greek: λαιμός, "throat") de ...

Land improvement Land development is the alteration of landscape in any number of ways such as: * Changing landforms from a natural or semi-natural state for a purpose such as agriculture or House, housing * subdivision (land), Subdividing real estate into Lot (re ...

- Lateral earth pressure -

Leaching (agriculture) In agriculture, leaching is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive ...

Leaching (pedology) In pedology, leaching is the removal of soluble materials from one zone in soil to another via water movement in the profile. It is a mechanism of soil formation distinct from the soil forming process of eluviation, which is the loss of mineral a ...

- Leaching model (soil) -

Leptosols A Leptosol in the World Reference Base for Soil Resources (WRB) is a very shallow soil over hard rock or a deeper soil that is extremely gravelly and/or stony. Leptosols cover approximately 1.7 billion hectares of the Earth's surface. They are f ...

Lessivage Lessivage is a kind of leaching from clay particles being carried down in suspension. The process can lead to the breakdown of peds (the particles that give the soil its characteristic structure). See also *Eluvium *Erosion *Leaching (agriculture ...

- Liming (soil) - Linear aeration - Lixisols -

Loam Loam (in geology and soil science) is soil composed mostly of sand (particle size > ), silt (particle size > ), and a smaller amount of clay (particle size < ). By weight, its mineral composition is about 40–40–20% concentration of sand–sil ...

Loess Loess (, ; from german: Löss ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loess or similar deposits. Loess is a periglacial or aeolian ...

- Lunar soil

M

Martian soil Martian soil is the fine regolith (a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock) found on the surface of Mars. Its properties can differ significantly from those of terrestrial soil, including its to ...

Miami (soil) The Miami soil series is the list of U.S. state soils, state soil of Indiana. The less sloping Miami soils are used mainly for maize, corn, soybeans, or winter wheat. The steeper areas are used as pasture, hayland, or woodland. Significant area has ...

- Multi-Scale Soil Information Systems -

Mineralization (soil science) Mineralization in soil science is the decomposition (i.e., oxidation) of the chemical compounds in organic matter, by which the nutrients in those compounds are released in soluble inorganic forms that may be available to plants. Mineralization ...

Mollisols Mollisol is a soil type which has deep, high organic matter, nutrient-enriched surface soil (a horizon), typically between 60 and 80 cm in depth. This fertile surface horizon, called a mollic epipedon, is the defining diagnostic feature of M ...

Mud A MUD (; originally multi-user dungeon, with later variants multi-user dimension and multi-user domain) is a Multiplayer video game, multiplayer Time-keeping systems in games#Real-time, real-time virtual world, usually Text-based game, text-bas ...

- Multiscale European Soil Information System -

Muskeg Muskeg (Ojibwe: mashkiig; cr, maskīk; french: fondrière de mousse, lit. ''moss bog'') is a peat-forming ecosystem found in several northern climates, most commonly in Arctic and boreal areas. Muskeg is approximately synonymous with bog or ...

- Myakka (soil)

N

Narragansett (soil) -

Natchez silt loam In 1988, the Professional Soil Classifiers Association of Mississippi selected Natchez silt loam soil to represent the soil resources of the State. These soils exist on 171,559 acres (0.56% of state) of landscape in Mississippi. Mississippi state ...

- National Society of Consulting Soil Scientists -

Natural organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...

Newmark's influence chart {{cleanup, reason=Formatting of mathematical formulas., date=March 2018 Newmark's Influence Chart is an illustration used to determine the vertical pressure at any point below a uniformly loaded flexible area of soil of any shape. This method, like ...

- No till method

O

On-Grade Mat Foundation for Expansive Soils - OPAL Soil Centre - Orovada (soil) -

Orthent Orthents are soils defined in USDA soil taxonomy as entisols that lack due to either steep slopes or parent materials that contain no permanent weatherable minerals (such as ironstone). Typically, Orthents are exceedingly shallow soils. They ar ...

- Overburden pressure -

Oxisol Oxisols are a soil order in USDA soil taxonomy, best known for their occurrence in tropical rain forest within 25 degrees north and south of the Equator. In the World Reference Base for Soil Resources (WRB), they belong mainly to the ferralsols ...

P

Paleosol -

Particle size (grain size) Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which refer ...

Paxton (soil) The Paxton soil series was established in Worcester County, Massachusetts in 1922, and is named for the town of Paxton where it was first described and mapped, and is the state soil of Massachusetts. Taxonomic classification Coarse-loamy, mixed, ...

Peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...

Pedalfer Pedalfer is composed of aluminum and iron oxides. It is a subdivision of the 1938 USDA soil taxonomy, zonal soil order comprising a large group of soils in which sesquioxides increase relative to silica during pedogenesis, soil formation. Pedalfers ...

Pedocal Pedocal is a subdivision of the zonal soil order. It is a class of soil which forms in semiarid and arid regions. It is rich in calcium carbonate and has low soil organic matter. With only a thin A horizon (topsoil), and intermittent precipitati ...

Pedodiversity Pedodiversity is the variation of soil properties (usually characterised by soil classes) within an area. Pedodiversity studies were first started by analyzing soil series–area relationships (Beckett and Bie, 1978). According to Guo et al. (2003 ...

- Pedology - Permeability (earth sciences) -

Petrichor Petrichor () is the earthy olfaction, scent produced when rain falls on dry soil. The word is constructed , the ichor, ethereal fluid that is the blood of the gods in Greek mythology. Origins Long before this phenomenon received its name in 19 ...

Plaggen soil Plaggen soil or plaggic anthrosol is a type of soil created in parts of northwest Europe in the Middle Ages, as a result of so-called "plaggen" agriculture on marginal podzol soils. In order to fertilize the fields, pieces of heath or grass includ ...

- Plainfield (soil) - Planosol - Plough pan - Podzol -

Pore water pressure Pore water pressure (sometimes abbreviated to pwp) refers to the pressure of groundwater held within a soil or rock, in gaps between particles ( pores). Pore water pressures below the phreatic level of the groundwater are measured with piezometers. ...

Porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

- Port Silt Loam -

Prime farmland Prime farmland is a designation assigned by U.S. Department of Agriculture defining land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops and is also available for th ...

Psamment In USDA soil taxonomy, a Psamment is defined as an Entisol which consists basically of unconsolidated sand deposits,Pygmy forest In anthropology, pygmy peoples are ethnic groups whose average height is unusually short. The term pygmyism is used to describe the phenotype of endemic short stature (as opposed to disproportionate dwarfism occurring in isolated cases in a po ...

Q

Quick clay Quick clay, also known as Leda clay and Champlain Sea clay in Canada, is any of several distinctively sensitive glaciomarine clays found in Canada, Norway, Russia, Sweden, Finland, the United States and other locations around the world. The clay ...

Quicksand Quicksand is a colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a ...

R

Rankers -

Red Mediterranean soil Terra rossa (Italian for "red soil") is a well-drained, reddish, clayey to silty soil with neutral pH conditions and is typical of the Mediterranean region. The reddish color of terra rossa is the result of the preferential formation of hematite ...

Regosols A Regosol in the World Reference Base for Soil Resources (WRB) is very weakly developed mineral soil in unconsolidated materials. Regosols are extensive in eroding lands, in particular in arid and semi-arid areas and in mountain regions. Internat ...

- Rendzina -

Residual Sodium Carbonate Index The residual sodium carbonate (RSC) index of irrigation water or soil water is used to indicate the alkalinity hazard for soil. The RSC index is used to find the suitability of the water for irrigation in clay soils which have a high cation exchan ...

Reynolds' dilatancy Dilatancy is the volume change observed in granular materials when they are subjected to shear deformations. This effect was first described scientifically by Osborne Reynolds in 1885/1886 Reynolds, O., "Experiments showing dilatancy, a property ...

- Rill -

Rock flour Rock flour, or glacial flour, consists of fine-grained, silt-sized particles of rock, generated by mechanical grinding of bedrock by glacial erosion or by artificial grinding to a similar size. Because the material is very small, it becomes suspe ...

S

SahysMod -

Saline seep A saline seep is seep of saline water, with an area of alkali salt crystals that form when the salty water reaches the surface and evaporates. Various types of water movement form saline seeps, including capillary action from a water table under t ...

- Salinity in Australia -

Salt marsh A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated ...

- Salting the earth -

SaltMod SaltMod is computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable, and the drain discharge (hydrology) in irrigated agricultural lands, using different (geo)hydrologic cond ...

San Joaquin (soil) San Joaquin is an officially designated state insignia, the state soil of the U.S. state of California. The California Central Valley has more than 500,000 acres (2,000 km²) of San Joaquin soils, named for the south end of that valley. Thi ...

Sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

- Sand boil - Sandbag - Scobey (soil) - Seitz (soil) -

Serpentine soil Serpentine soil is an uncommon soil type produced by weathered ultramafic rock such as peridotite and its metamorphic derivatives such as serpentinite. More precisely, serpentine soil contains minerals of the serpentine subgroup, especially anti ...

- Shear strength (soil) - Shear strength test -

Shrub swamp Shrub swamps — also called scrub swamps or buttonbush swamps — are a type of freshwater wetland ecosystem occurring in areas too wet to become swamps (“true” or freshwater swamp forest), but too dry or too shallow to become marshes. They ...

Silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...

Slope stability Slope stability analysis is a static or dynamic, analytical or empirical method to evaluate the stability of earth and rock-fill dams, embankments, excavated slopes, and natural slopes in soil and rock. Slope stability refers to the condition of i ...

- Slump - Sodium adsorption ratio -

Soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

- Soil acidification -

Soil amendment A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...

Soil and water assessment tool Soil and Water Assessment Tool (SWAT) is a free and open source software, open source hydrology model and Geographic Information System, GIS computer simulation sponsored by the USDA. SWAT is a well known geographic hydrological model in use by m ...

- Soil Association - Soil biodiversity -

Soil biology Soil biology is the study of microbial and faunal activity and ecology in soil. Soil life, soil biota, soil fauna, or edaphon is a collective term that encompasses all organisms that spend a significant portion of their life cycle within a soil ...

Soil carbon Soil carbon is the solid carbon stored in global soils. This includes both soil organic matter and inorganic carbon as carbonate minerals. Soil carbon is a carbon sink in regard to the global carbon cycle, playing a role in biogeochemistry, clima ...

Soil cement Soil cement is a construction material, a mix of pulverized natural soil with small amount of portland cement and water, usually processed in a tumbler, compacted to high density. Hard, semi-rigid durable material is formed by hydration of the cem ...

- Soil chemistry - Soil classification -

Soil compaction In geotechnical engineering, soil compaction is the process in which stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water (or other ...

Soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...

- Soil conservation -

Soil Conservation and Domestic Allotment Act The Soil Conservation and Domestic Allotment Act , enacted February 29, 1936) is a United States federal law that allowed the government to pay farmers to reduce production so as to conserve soil and prevent erosion. Legislative history The Act ...

- Soil Conservation and Domestic Allotment Act of 1936 - Soil contamination - Soil crust -

Soil depletion Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent Crop yield, yields of high quality.

- Soil ecology -

Soil erosion Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and ...

Soil fertility Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality.

Soil food web The soil food web is the community of organisms living all or part of their lives in the soil. It describes a complex living system in the soil and how it interacts with the environment, plants, and animals. Food webs describe the transfer of en ...

Soil functions Soil functions are general capabilities of soils that are important for various agricultural, environmental, nature protection, landscape architecture and urban applications. Soil can perform many functions and these include functions related to th ...

Soil gradation Soil gradation is a classification of a coarse-grained soil that ranks the soil based on the different particle sizes contained in the soil.Holtz, R. and Kovacs, W. (1981), ''An Introduction to Geotechnical Engineering'', Prentice-Hall, Inc. Soi ...

Soil guideline value Soil Guideline Values (SGVs) are figures which are used in non-statutory technical guidance for assessors carrying out risk assessments to determine whether land is considered Contaminated land, ‘contaminated’ under United Kingdom law, that is ...

- Soil health -

Soil horizon A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...

- Soil inoculant - Soil life -

Soil liquefaction Soil liquefaction occurs when a cohesionless saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake or other sudden change in stress condition, in ...

- Soil management - Soil mechanics -

Soil moisture Soil moisture is the water content of the soil. It can be expressed in terms of volume or weight. Soil moisture measurement can be based on ''in situ'' probes (e.g., capacitance probes, neutron probes) or remote sensing methods. Water that enters ...

Soil moisture sensors Soil moisture sensors measure the volumetric water content in soil. Since the direct Gravimetric analysis, gravimetric measurement of free soil moisture requires removing, drying, and weighing of a sample, soil moisture sensors measure the volumet ...

Soil nailing Soil nailing is a remedial construction measure to treat unstable natural soil slopes or unstable man-made (fill) slopes as a construction technique that allows the safe over-steepening of new or existing soil slopes. The technique involves the in ...

Soil organic matter Soil organic matter (SOM) is the organic matter component of soil, consisting of plant and animal detritus at various stages of decomposition, cells and tissues of soil microbes, and substances that soil microbes synthesize. SOM provides numerous b ...

Soil pH Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...

Soil physics Soil physics is the study of soil's physical properties and processes. It is applied to management and prediction under natural and managed ecosystems. Soil physics deals with the dynamics of physical soil components and their phases as solid ...

- Soil policy (Victoria, Australia) - Soil profile -

Soil resilience Soil resilience refers to the ability of a soil to resist or recover their healthy state in response to destabilising influences. This is a subset of a notion of '' environmental resilience''. Overview Soil resilience should first be looked at ...

Soil respiration Soil respiration refers to the production of carbon dioxide when soil organisms respire. This includes respiration of plant roots, the rhizosphere, microbes and fauna. Soil respiration is a key ecosystem process that releases carbon from the ...

Soil salinity Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization. Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the ...

- Soil salinity control -

Soil science Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to th ...

- Soil Science Society of America - Soil series -

Soil solarization Soil solarization is a non-chemical environmentally friendly method for controlling pests using solar power to increase the soil temperature to levels at which many soil-borne plant pathogens will be killed or greatly weakened. Soil solarization ...

- Soil steam sterilization - Soil structure -

Soil survey Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former term ...

- Soil test - Soil texture -

Soil type A soil type is a taxonomic unit in soil science. All soils that share a certain set of well-defined properties form a distinctive soil type. Soil type is a technical term of soil classification, the science that deals with the systematic categoriz ...

Soil water (retention) Soils can process and hold considerable amounts of water. They can take in water, and will keep doing so until they are full, or until the rate at which they can transmit water into and through the pores is exceeded. Some of this water will steadil ...

- Soils retrogression and degradation - Solonchak - Solonetz -

Specific storage In the field of hydrogeology, ''storage properties'' are physical properties that characterize the capacity of an aquifer to release groundwater. These properties are storativity (S), specific storage (Ss) and specific yield (Sy). According to '' ...

- Specific weight - Spodic soils - Stagnosol -

Strip farming Strip cropping is a method of farming which involves cultivating a field partitioned into long, narrow strips which are alternated in a crop rotation system. It is used when a slope is too steep or when there is no alternative method of preventin ...

Stuttgart (soil) Stuttgart soil series is an officially designated state symbol, the State Soil of Arkansas. Stuttgart soils are named for the City of Stuttgart in southeast Arkansas. They are used primarily for crops, mainly rice, soybeans, small grains, and ...

Subaqueous soil Subaqueous soils are soils formed in sediment found in shallow, permanently flooded environments or soils in any areas permanently covered by water too deep for the growth of rooted plants. The study of subaqueous soils is a relatively new field i ...

Subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...

Subsoil Subsoil is the layer of soil under the topsoil on the surface of the ground. Like topsoil, it is composed of a variable mixture of small particles such as sand, silt and clay, but with a much lower percentage of organic matter and humus, and it ...

T

Talik A talik is a layer of year-round unfrozen ground that lies in permafrost areas. In regions of continuous permafrost, taliks often occur underneath shallow thermokarst lakes and rivers, where the deep water does not freeze in winter and thus the ...

- Tanana (soil) -

Technosols A Technosol in the World Reference Base for Soil Resources is a Reference Soil Group that combines soils whose properties and pedogenesis are dominated by their technical origin. They contain either a significant amount of artefacts (something in t ...

Tepetate Tepetate (Spanish ''tepetate''; Nahuatl ''tepetlatl'') is a Mexican term for a geological horizon, hardened by compaction or cementation, found in Mexican volcanic regions. Tepetates at the surface are problematic for agriculture, because of thei ...

Terrace (agriculture) In agriculture, a terrace is a piece of sloped plane that has been cut into a series of successively receding flat surfaces or platforms, which resemble steps, for the purposes of more effective farming. This type of landscaping is therefore ...

- Terracette - Terramechanics -

Terra preta ''Terra preta'' (, locally , literally "black soil" in Portuguese) is a type of very dark, fertile anthropogenic soil ( anthrosol) found in the Amazon Basin. It is also known as "Amazonian dark earth" or "Indian black earth". In Portuguese its ful ...

Terra rosa (soil) Terra rossa (Italian for "red soil") is a well-drained, reddish, clayey to silty soil with neutral pH conditions and is typical of the Mediterranean region. The reddish color of terra rossa is the result of the preferential formation of hematite ...

Terzaghi's Principle Terzaghi's Principle states that when stress is applied to a porous material, it is opposed by the fluid pressure filling the pores in the material. Karl von Terzaghi's introduced the idea in a series of papers in the 1920s based on his examinatio ...

Thaw depth In soil science, the thaw depth or thaw line is the instantaneous level down to which the soil has warmed to zero degrees celsius. The active layer thickness is the maximum thaw depth over a period of two years. The layer of soil over the thaw dept ...

- Thixotropy -

Threebear (soil) Threebear soil is the official state soil of the U.S. state of Idaho. Profile The Threebear series consists of moderately well drained soils formed in silty sediments with a thick mantle of volcanic ash. These soils are moderately deep to a fragi ...

- Throughflow - Tifton (soil) -

Tillage Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoein ...

Topsoil Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs. Description Topsoil is composed of mineral particles and organic matt ...

Tropical peat Tropical peat is a type of histosol that is found in tropical latitudes, including South East Asia, Africa, and Central and South America. Tropical peat mostly consists of dead organic matter from trees instead of spaghnum which are commonly foun ...

U

Umbric horizon -

Ultisols Ultisols, commonly known as red clay soils, are one of twelve soil orders in the United States Department of Agriculture soil taxonomy. The word "Ultisol" is derived from "ultimate", because Ultisols were seen as the ultimate product of continu ...

Umbrisols In soil classification, an Umbrisol is a soil with a dark topsoil and in which organic matter has accumulated within the mineral surface soil—in most cases with low base saturation—to the extent that it significantly affects the behavi ...

- Unified Soil Classification System -

USDA soil taxonomy USDA soil taxonomy (ST) developed by the United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters (most commonly their properties) and in sev ...

- Ustochrept

V

Vegetation and slope stability Vegetation and slope stability are interrelated by the ability of the plant life growing on slopes to both promote and hinder the stability of the slope. The relationship is a complex combination of the type of soil, the rainfall regime, the plan ...

- Vertisol -

Vibro stone column Vibro stone columns or aggregate piers are an array of crushed stone pillars placed with a vibrating tool into the soil below a proposed structure. This method of ground improvement is also called vibro replacement. Such techniques increase the loa ...

Void ratio The void ratio of a mixture is the ratio of the volume of voids to volume of solids. It is a dimensionless quantity in materials science, and is closely related to porosity as follows: :e = \frac = \frac = \frac and :\phi = \frac = \frac = \fr ...

W

Water content -

Weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

- Windsor (soil) -

World Congress of Soil Science The World Congress of Soil Science (WCSS) is a conference held every four years (although interrupted by World War II) under the guidance of the International Union of Soil Sciences (IUSS). The purpose of a congress is to: (i) ensure the advancem ...

Y

Yedoma