Glossary of Pedology
A B C D E F G H I J K L M N O P Q R S T U V X Z W
A
Acric: chemical condition of a deeply weathered soil, presenting a B horizon characterized by low cation retention value (CR ≤ 1.5) and ∆pH value positive or null; or CR 1.5 and pH ( KCl ) > 5.0. In Brazil , such soils occur mainly at the States of Goiás , Minas Gerais ("Triângulo Mineiro"), Mato Grosso do Sul and northeast region of the São Paulo State (South American surface). Acric soils are usually very dry due to the strong clay micro-aggregation that causes fast water movement downward the soil profile. During field test, this soil gives the sand sensation in your hands and at first sight seems medium texture, but when wetted and hand-squeezed its clayey or very clayey texture is evidenced. Below the arable layer, it has low nutrient contents, CEC values and sum of bases (calcium, potassium and magnesium), but do not present high aluminum saturation values (m < 50%). When ∆pH is positive below the arable layer, it means that soil base concentrations (calcium, magnesium, potassium and sodium) are very low and the anion retention (sulfate, chloride, nitrate, etc.) is higher than the cation retention (calcium, magnesium, potassium and sodium). According to LANDELL (IAC - Sugarcane Research Center), the average yield of five sugarcane cuts ranges between 76-80 t ha-1 in the Acric Oxisols at the Ribeirão Preto region (State of São Paulo), but it is much lower (below 68 t ha-1) in the Acric Oxisols of Goianésia (State of Goiás), because this latter is a drier region. Yearly cycle crop plants (maize, soybeans, etc), may present high yields when grown in these soils, but require medium to high tech management level.
Alic: chemical condition of very poor soil below the arable layer (B or C horizon, or A horizon of the Litholic Neosols), due to high aluminum saturation values (m 50% and at the same time Al concentrations ranging between 0.3 and 4.0 cmol kg-1). These soils are present overall States of Brazil. Therefore, alic soil management requires gypsum application to improve the chemical environment below the arable layer, where toxic Al concentrations restrict root growth in depth. Consequently, the soil calcium, magnesium and potassium concentrations (sum of bases) are very low, because most CEC electrical charge sites are occupied with aluminum. It has been observed that gypsum application is well succeeded when the soil clay CEC is lower than 27 cmol kg-1 of soil, in the B horizon.
Alluviation : is the process of soil formation by horizontal transport of clay, silt, sand, gravel and organic matter by rivers or streamlets, and posterior deposition forming the soil profile in marginal dicks of rivers and streams. According to the new EMBRAPA nomenclature, the soil formed is a Fluvic Neosol .
Alluvion : is a term which describes the increase in the plain area of land due to sediment (alluvium) which is deposited by a river forming sedimentary clastic rocks.
Alluvium: is soil or sediments deposited by a river or other running water, typically made up of a variety of materials (including fine particles of silt and clay and larger particles of sand and gravel) .
Alteration: rock degrading by physical processes such as decompression caused by upper rock layers removal; salt, ice and root action into the fissures, and also by wind abrasion.
Aluminic: chemical condition of very poor soils below the arable layer (in general B horizon) due to very high aluminum (Al) saturation values (m and at the same time with Al concentrations greater than 4.0 cmol kg-1). The aluminic soils differ from alic soils by their higher Al concentrations in the B horizon.
Arenite: is a sedimentary clastic rock formed by sand fraction grains (0.063 mm and 2 mm).
Argilite: is a sedimentary clastic rock formed mainly by grains of clay particle sizes (< 0.002 mm).
Auger: sampling device used to collect soil samples.
B
Basalt: is a common mafic extrusive volcanic rock, poor in silica and rich in iron and magnesium. It is usually gray to black and fine-grained due to rapid cooling of lava. Occurring chemical weathering, clay minerals provide considerable amounts of calcium, magnesium, potassium and sodium to the soil.
Basin (hydrographic) : a hydrographic basin is (1) an area contributing with water and sediments to a river; (2) the drainage basin of a stream; and (3) an area occupied by a lake and its drainage basin .
Bauxite: a luminum ore most commonly formed in deeply weathered rocks. In some locations, deeply weathered volcanic rocks, usually basalt. It is essentially formed of Al-hydroxides (gibbisite, boehmite and diaspore).
Biotite: is a common phyllosilicate mineral within the mica group, of black-greenish color rich in potassium between the structure unities.
Brunizem: Class of dark-brown prairie mineral soils, non-hydromorphic, with chernozemic A horizon, and eutrophic B horizon; presenting CEC > 27 cmol kg-1 of clay (Ta), including the organic matter of textural B horizon or incipient B horizon, according to Camargo et al (1987); or textural B, nitic B or incipient B horizon of the Chernosols order, according to EMBRAPA (1999). In the USA Soil Taxonomy System it is related to the Mollisols order.
Bruno non - calcic: is a class of mineral soil, non-hydromorphic, generally showing weak A horizon and reddened eutrophic B horizon [CEC > 27 cmol kg-1 of clay (Ta) including the organic matter of the textural B horizon] according to Camargo et al. (1987); or textural B horizon of the Luvisols order according to EMBRAPA (1999) nomenclature. And it is connected to the Alfisols in the USA Soil Taxonomy System.
C
Calcification: soil formation process through the accumulation of calcium carbonate.
Calcite: is carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3).
Cation exchange capacity (CEC): is the clay capacity of adsorb chemical elements and exchange them by other elements in the soil solution. It is determined by the sum of positively charged elements, that is, the sum of bases (SB) (calcium + magnesium + potassium + sodium) plus aluminum and hydrogen. Therefore, the clay CEC is the total negatively charged electrical sites in the clay surface that bound to the positively charged elements, which are the main soil cation nutrients and also aluminum (Al) and hydrogen (H) . CEC = SB + Al + H, determined at soil pH = 7.
Chroma: The difference from gray at a given hue and lightness in the Munsell color system . Soil color intensity component that indicates the color purity and the proportion of black and white for a certain hue (red and yellow) and it is indicated in the rows across the page from as low as 0 to as much as 8 in the Münsell table.
Clastic : loose rock fragment.
Clay of high activity (Ta): B horizon with CEC 27 cmol kg-1 of clay, including the organic matter contribution. T is calculated by the formula: T = [CEC ( cmol kg-1 of soil) x 100] / %clay
Clay of low activity (Tb): B horizon with CEC < 27 cmol kg-1 of clay, including the organic matter contribution. T is calculated by the formula: T = [CEC (cmol kg-1 of soil) x 100] / %clay
Clay: granulometric fraction of grain size lower than 0.002 mm. Also, class of minerals termed silicates (kaolinite, montmorillonite, illite, etc.).
Colluvium: is the name for loose bodies of sediment that have been deposited or built up at the bottom of a low grade slope.
Color: s oil color is characterized by three features: hue, value, and chroma. Hue refers to the soil color in relation to red, yellow. Value refers to the lightness of the hue (proportion of black and white colors). Chroma refers to the strength of the color (proportion of red, yellow, black and white, or color purity). Soil colors are determined by use of a Munsell Color Book (Munsell Color, 1975): it has color charts of different hues, ranging from 10R to 10Y. Each page of hue has color chips that show values and chromas . Values are shown in columns down the page from as low as 0 to as much as 10, and chromas are shown in rows across the page from as low as 0 to as much as 8. In writing Munsell color notations, the sequence is always hue, value, and chroma (e.g. 10YR5/2).
Conglomerate: consolidated deposition formed by cemented gravel fragments.
D
Depression: in geology is a landform sunken or depressed below the surrounding area. Depressions may be formed by various mechanisms, and may be referred to by a variety of technical terms.
Desertification (or desertization) is the degradation of land in arid, semi arid and dry sub-humid areas resulting primarily from human activities and influenced by climatic variations. Climate and life processes, expansion of desert regions, savanna vegetation.
Dick (marginal dick) : special form of alluvial sediment accumulation in river margins.
Doline : sink or sinkhole is a closed depression draining underground in karst areas ( the landscape is largely shaped by the dissolving action of water on carbonate bedrock, usually limestone). A doline can be cylindrical, conical, or bowl- or dish-shaped. The diameter ranges from a few to many hundreds of meters.
Dolomite: mineral of calcium and magnesium carbonate composition [Ca.Mg (CO3)2], the main mineral component of dolomitic limestone.
Drainage (dendritic pattern): the d endritic drainage pattern takes the form of "dendrites" and looks like the branching roots of a tree. In practice, this type of drainage pattern is typical of areas where mainly Ultisols, Luvisols, Cambisols and Litholic Neosols occur.
Drainage (external): water removal through the soil surface (runoff).
Drainage (internal): internal water flow movement through the pores of soil profile horizons or layers. According to the water flow velocity, the drainage can be excessive, strong, good, moderate, poor and very poor.
Drainage (parallel pattern): the parallel drainage pattern is a pattern of rivers caused by steep slopes with some relief. Because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction. In practice, this drainage pattern is typical of areas where mainly Oxisols and Quartzarenic Neosols occur.
Dunes: sand hills of varied shapes and sizes built by eolian processes (wind action).
Duripan: is a diagnostic soil horizon that is cemented by illuvial silica into a subsurface hardpan . And it can be as hard as concrete which makes plowing very difficult to impossible. It does not solubilize in water or hydrochloric acid.
Dystrophic: chemical condition below the arable layer (B or C horizon when there is no B horizon; or A horizon in the Litholic Neosols) with low sum of bases (SB) and low base saturation (V) values. According to PRADO, dystrophic soils present V values ranging between 30 and 50%, but at the same time, SB values lower than 1.2 cmol kg-1 of soil. Also are dystrophic soils the ones that present V< 30%, but at the same time, low aluminum saturation (m < 50%) and high cation retention (CR >1.5 cmol kg-1), excluding the possibility of confusion with the alic or acric adjective terms. These soils require different management, because despite their poor nutritional potential below the arable layer, they have lower aluminum contents.
E
Edaphology: is the science that deals with the influence of soil and other media on the growth of plants.
Eluvium : in soil science, eluvium or eluvial deposits are those soil deposits that are derived by in situ weathering or weathering plus gravitational movement or accumulation. The process of removal of materials from soil horizons is called eluviation . In soil science, eluviation is the transport of soil material from upper layers of soil to lower levels by downward precipitation of water across soil horizons.
Eutrophic: chemical condition of a soil showing high nutritional potential below the arable layer (B horizon, or C horizon when there is no B horizon, or A horizon of Litholic Neosols). These soils present sum of bases (SB) values 1.5 cmol kg-1 of soil, and base saturation values (V) 50%. They are high productivity soils, since salinity is not simultaneously present, like some cases occurring in the northeast region of Brazil. Eutrophic soils occur in all Brazilian States.
F
Factors of soil formation: agents of soil formation such as climate, parent material, organisms, relief and weather.
Family: category of the soil classification system that includes data required for soil management (texture, mineralogy, acidity degree, depth) for agriculture purposes or not.
Feldspar: aluminum-silicate mineral containing potassium, sodium and calcium commonly found in igneous and metamorphic rocks. Clays are originated from this mineral chemical alteration.
Firm: a firm soil is consistent, when moistened and moderately pressed between fingers.
Floculation : clay flocculation is the clay precipitation forming aggregates.
Floodplain : floodable lowlands around rivers.
Friable: A friable soil is the one that easily crumbles in your hands when slightly pressed between fingers. A friable soil allows easy cultivation.
G
GIS: A geographic information system (GIS), also known as geospatial information system , is any system for capturing, storing, analyzing, managing and presenting data and associated attributes which are spatially referenced to Earth. In certain countries such as Canada, GIS is more well known as Geomatics. The other definition is, GIS is a system or tool or computer based methodology to collect, store, manipulate, retrieve and analyse spatially (georeferenced) data.
Gleization: a process of soil formation in saturated or nearly saturated (hydromorphism) soil conditions which involves the reduction of iron, its segregation into mottles and concretions, forming the typical gley horizon of Gleysols.
Gley ( Humic gley soil): class of hydromorphic soil, rich in organic material, and occupy low depth areas. It presents a prominent A or chernozemic A horizon, according to Camargo et al. (1987); suborder Gleysol Melanic according to EMBRAPA (1999). According to the USA Soil Taxonomy, it is related to the suborders Aquox , or Aquept , or Aqualf , or Aquult .
Gley (Low humic gley soil): class of hydromorphic soil, with moderate A horizon (according to Camargo et al., 1987); suborder Haplic Gleysol according to the EMBRAPA (1999). According to the USA Soil Taxonomy, it is related to the suborders Aquox , or Aquept , or Aqualf , or Aquult .
Granite: it is a common and widely occurring type of intrusive, felsic, igneous rock, constituted of quartz, mica, feldspar and acessory minerals. Outcrops of granite tend to form tors, and rounded massifs. Granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels. It is very resistent to chemical weathering and, consequently, present little developed soils.
Gravel: is any loose rock fragment, which diameter is at least two millimeters (2 - 20 mm).
H
Hematite: iron oxide (Fe2O3) responsible for the soil red color.
Hillside: The side or slope of a hill, situated between the foot and the summit.
Horizon (A): the outermost (most superficial) soil horizon in a soil profile is termed the "A" horizon (once not eroded). Generally, it presents darker color, due to root decomposition, and high microbiological activity. It is considered an alluvial horizon, because its fine particles and soluble substances can move down in depth accumulating into the B horizon. It is also considered, the diagnostic superficial horizon, but it is not necessarily correspondent to the epipedon of the USA Soil Taxonomy. A n epipedon is not the same as an A horizon, because the epipedon may include part or all of an illuvial B horizon if the darkening by organic matter extends from the soil surface into the B horizon).
Horizon (AB): the transitional horizon between A and B horizons, which characteristics are closer to the A horizon; AB horizon was previously termed A3 horizon.
Horizon (B): the illuvial horizon, that is, it accumulates the particles displaced from A horizon. It is commonly referred to as ‘subsoil' and presents the maximal expression of soil color, texture, structure and serosity (if it exists). It is the diagnostic horizon, that is, the main horizon for soil classification.
Horizon (BA): the transitional horizon between A and B horizons , which characteristics are closer to the B horizon; BA horizon was previously termed B1.
Horizon (BC): the transitional horizon between B and C horizons, which characteristics are much closer to the C than to the B horizon. BC horizon was previously termed B3.
Horizon (soil horizon): a specific soil layer, which is parallel to the soil surface and presents physical characteristics which differ from the layers above and beneath by color, texture and structure. Horizon formation is a function of a range of geological, chemical, and biological processes and occurs over long time periods through weathering and parent material pedogenesis (in general rock material).
Horizon (C): the soil parent material from which the A and B horizons were developed along the time through the weathering action.
Hue or Nuance: the color hue or nuance represents the combination of red and yellow and for soil colors may vary from 10R (100% red and 0% yellow) to as much as 10Y (100% yellow and 0% red). For instance, the hue 5YR is a combination of 50% red plus 50% yellow; and the 7.5YR is 62.5% yellow plus 37.5% red; and in the 10Y is 0% red and 100% yellow. In the case of the color notation 5YR 5/3, the hue or nuance is given by 5YR.
I
Illuvium: is material (silicate clays, organic matter and iron and aluminum hydroxides) displaced across a soil profile, in depth, by the action of rainwater. The process of deposition of illuvium is termed illuviation and i t is a water-assisted transport in basically vertical direction, as compared to alluviation, the horizontal running water transfer. The resulting deposits are called illuvial deposits.
J
Jarosite: is a mineral of basic hydrous sulfate of potassium and iron. This mineral is formed in ore deposits by the oxidation of iron sulfides in a soil sulfuric horizon.
K
Ki: is the silica/aluminum molecular ratio (Ki = SiO2/Al2O3 x 1.7), that represents the soil weathering degree. The lower the Ki index the higher the soil weathering degree, indicating that silica has been intensively removed from the system.
K w: is the soil weathering index calculated by: [Kw = SiO2/Al2O3 x 1.7]. The lower the Kw value the more weathered is the soil. This index evaluates the soil clay fraction decomposition degree. For example, the Kw values in the decreasing weathering sequence are as follows: montmorillonite Kw (2:1 type clay) > kaolinite Kw (1:1 type clay) > gibbisite Kw (Al oxides).
Krasnozem: A Great Soil Group, which soils are typically red, deep, well-structured, acid and porous soils. They have relatively high clay contents and tend to display a gradual increase in clay with depth. It corresponds to the Red Nitosol in the Brazilian System of Soil Classification.
L
Laterite: is a material formed in hot and wet tropical areas which is rich in iron and aluminum, poor in organic matter, and developed by intensive and long lasting weathering of the underlying parent rock. It turns irreversibly hardened in contact with air.
Latosol : class of deep soils with low textural gradient between A and B horizons, low CEC, low or null primary mineral contents, easily weathered, presenting low Kw index, according to the criteria of Camargo et al. (1987) and EMBRAPA (1999). It corresponds to the Oxisol order in the USA Soil Taxonomy.
Latosolization: process of soil formation characterized by a high silica displacement during the weathering process; this term substitutes the term lateritization , the same as ferritization.
Layer: soil material constituted of mineral and organic compounds which origin was not influenced by soil formation factors (such as climate, parent material, relief, organisms and time) and by pedogenetic processes.
Lessivage: mechanical migration or translocation of clay from A to B textural horizon or nitic B horizon.
M
Mesoalic: term used to designate an intermediate chemical condition between dystrophic and alic soil attributes beneath the arable layer (B horizon, or C horizon in case of B horizon does not exist, or A horizon in the Litholic Neosols). According to PRADO, H., mesoalic soils present aluminum saturation (m) values ranging between 15 and 50%, and at the same time, aluminum contents 0.4 cmol kg-1 of soil. These soils occur all over the Brazilian States.
Mesotrophic: term used to designate an intermediate chemical condition between dystrophic and eutrophic soil attributes beneath the arable layer (B horizon, or C horizon when there is no B horizon, or A horizon in the Litholic Neosols). According to PRADO, H., a mesotrophic soil sum of bases (SB) ranges between 1.2 and 1.5 cmol kg-1 of soil, and at the same time, the base saturation (V%) ranges between 30-50%; or else, when V > 50%, but SB is lower than 1,5 cmol kg-1 of soil.
Mica: type 2:1 clay mineral ( sheet silicate mineral) presenting two layers of tetrahedral silicate and one layer of octahedral aluminum.
Mineral (felsic): Felsic minerals are referred to silicate minerals which are poor in iron and enriched in the lighter elements such as silicon, oxygen, aluminum, sodium, and potassium. The term combines the words "feldspar" and "silica." Felsic minerals are usually light in color (quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars) .
Mineral (mafic): mafic mineral is a silicate mineral that is rich in magnesium and iron. Most mafic minerals are dark in color (olivine, pyroxene, amphibole, and biotite). Common mafic rocks include basalt and gabbro.
Mineral: inorganic material with well-defined chemical composition and crystalline structure. Ex.: quartz, feldspar.
Mineraloid: is a mineral-like substance with defined chemical composition that does not demonstrate crystallinity. Ex.: water in the liquid state.
Morphogenesis: all processes that give origin to the landscape relief forms. Morphogenesis and pedogenesis (or soil evolution, or formation, is the process by which soil is created) can in certain situations be opposite, because soil genesis might be retarded or inhibited in places where the morphogenetic processes are more intense, like for instance in beaches and dunes.
N
Nuance or Hue: the color hue or nuance represents the combination of red and yellow and for soil colors may vary from 10R (100% red and 0% yellow) to as much as 10Y (100% yellow and 0% red). For instance, the hue 5YR is a combination of 50% red plus 50% yellow; and the 7.5YR is 62.5% yellow plus 37.5% red; and in the 10Y is 0% red and 100% yellow. In the case of the color notation 5YR 5/3, the hue or nuance is given by 5YR.
O
Order: first level in the soil classification hierarchy.
Organic matter: when referred to as soil organic matter is the decaying plant and animal or living organism material that is decayed to the point it is no longer recognizable .
Oxisol: soil order of the American Soil Classification (Soil Taxonomy).
Oxides: iron, aluminum, manganese and titanium oxides and hydroxides with the same coordination number.
P
Peak: is the summit; t he highest point or part; the top; the highest altitude point of the landscape; line along which two opposite hillsides intercept each other.
Pedogenesis: soil evolution, soil formation; it is the process by which soil is formed.
Pedology: in soil science, it is the study of soils in its natural environment. Pedology deals with pedogenesis, soil morphology (color, texture, structure, etc.) and soil classification .
Pedon: The smallest (three-dimensional) unit or volume of soil that contains all the soil horizons of a particular soil type, usually having a surface area of approximately 1 square meter and extending from the ground surface down to bedrock.
Permeability: soil permeability refers to the soil porous space that can be occupied by solids (like roots), liquids and gases.
Petroplinthite: it is irreversibly hardened plinthite material (the term plinthite has substituted the term Laterite).
Photopedology: photographic interpretation of the landscape pedological condition.
Phyllite: phyllo (sheet) + ite (stone), it is a type of foliated metamorphic rock primarily composed of quartz, sericite mica, and chlorite; the rock represents a gradation in the degree of metamorphism between slate and mica schist.
Phyllosilicate: phyllo (sheet) + silicate (tetrahedral mineral atom arrangement of 1 silicon and 4 oxygen atoms). It is the clay mineral structure type of arrangement. The tetrahedral sheet is one of the two basic sheet components of the phyllosilicate minerals.
Plain (fluvial): fluvial plain is the area near rivers and streams with little declivity level .
Planosol: Class of hydromorphic soil with abrupt textural B horizon according to Camargo et al (1987); and a suborder of Hydromorphic Planosols according to the nomenclature of EMBRAPA (1999). Intrazonal group of soils underlain by B-horizons strongly compacted by material leached from surface horizons, developed on nearly flat uplands. In the USA Soil Taxonomy is related to the Aqualf or Aqult suborder.
Podzolization: a process of soil formation in which mechanical (clay, organic matter) or chemical (bases, Fe, Al) migration from A to B horizon occurs. When mechanical migration occurs the soil presents a textural B horizon and when chemical migration occurs the soil presents a spodic B horizon.
Porosity: soil or rock porosity is referred to the volume of pores ( void space in the material) that may contain air or water (not solid particles).
Profile: the soil profile is the series of horizon layers extending from the ground surface down to bedrock.
Pyrite: t he mineral pyrite , or iron pyrite , is an iron sulfide (formula FeS2) with metallic luster and pale-to-normal brass-yellow nuance.
Q
Quartz: is the most abundant mineral in the Earth's continental crust. It is made up of a lattice of silica (SiO2) tetrahedra. Quartz belongs to the rhombohedral crystal system .
Quartzite: is a hard, metamorphic rock which was originally sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to grey. Quartzites often occur in various shades of pink and red due to varying amounts of iron oxide. Other colors are commonly due to impurities of minor amounts of other minerals.
R
Ratio silica/alumina: see Ki
Ratio silt /clay: it is used to discriminate Oxisols from Cambisols together with other soil attributes.
Rendzina: Rendzina is a dark, grayish-brown, humus-rich soil. It is one of the soils most closely associated with the bedrock type and an example of initial stages of soil development. It is usually formed by weathering of soft rock types, most frequently carbonate rocks (dolomite, limestone, marl, chalk) but occasionally sulfate rocks (gypsum). It is a soil class according to Camargo et al. (1987); but belongs to the soil order of Chernosols according to Embrapa (1999) nomenclature. It is related to the soil order of Mollisols in USA soil taxonomy.
Rock (acidic): acidic rocks are igneous rocks with high silica content (> 65% of SiO2).
Rock (basic): basic rocks are igneous rocks with low silica content (52-45% of SiO2).
Rock (igneous): igneous rocks are rocks formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks .
Rock (intermediate): intermediate rocks are igneous rocks with intermediate silica content (52-65% of SiO2).
Rock (metamorphic): a metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith , subjected to heat and pressure (temperatures greater than 150 to 200 °C and pressures of 1500 bars) causing profound physical and/or chemical change. The protolith may be sedimentary rock, igneous rock or another older metamorphic rock.
Rock (sedimentary): sedimentary rock is one of the three main rock groups (the others being igneous and metamorphic rock). Rock formed from sediments transported by the water or ice. It covers 75-80% of the Earth's land area, and includes common types such as chalk, limestone, dolomite, sandstone, conglomerate and shale .
Rock (ultrabasic): ultrabasic rocks are igneous rocks with very low silica content (< 45% of SiO2).
S
Salinization: is the process of soil formation characterized by high salt accumulation and often occurs i n semiarid regions (on the rims of depressions and edges of drainage ways, at the base of hill slopes, and in flat, low-lying areas surrounding sloughs and shallow bodies of water). These areas receive additional water from below the surface, which evaporates, and the salts are left behind on the soil surface.
Sand: granulometric fraction of quartz particles with grain size between 0.002 and 2 mm.
Scarp: hillside of highest slope.
Silt: a sedimentary material consisting of very fine particles intermediate in size between sand and clay (particle diameter between 0.05 and 0.0002 mm in the USA scale, or 0.002 and 0.0002 mm in the international scale of Atterberg ).
Sink: duct buried into the soil to drain the excess water.
Soil (intermediate order): an intermediate soil differs from the two typical adjacent soils as concerned to the first level of soil taxonomy (order) on some morphological or chemical or mineralogical attributes. In the Brazilian System of Soil Classification, an intermediate soil belongs to the 4 th level or subgroup. For example: a Latosolic Eutrophic Red Nitosol and an Argisolic Red-Yellow Latosol (Oxisol). In the first example, the adjective " Latosolic" is justified by the lower serosity distinctness, lower structure development and lower B horizon friability just below a typical Nitic B horizon. In the second example, the adjective "Argisolic" is justified by the slightly greater textural gradient than the observed in a Latosol (Oxisol), since that the Latosol (Oxisol) morphological attributes are maintained.
Soil (typical): a typical soil fulfills all requirements (criteria) of the first level (order) of soil classification. For example: a typical Eutrophic Red Nitosol , a typical Red-yellow Oxisol (Hapludox). These soils correspond to the 4th level or subgroup, in the Brazilian System of Soil Classification.
Soil: is the naturally occurring, unconsolidated or loose covering of broken rock particles and decaying organic matter (humus) on the surface of the Earth, capable of supporting life.
Solonization: th is process begins with the leaching of salt by rainwater, causing clay dispersion. The Sodic Planosol (according to the nomenclature of EMBRAPA, 1999; previously termed Solodized Solonetz) was formed by the solonization process.
Solum : The solum (plural, sola) in soil science consists of the surface (A horizon) and subsoil (B horizon) layers that have undergone the same soil forming conditions. The base of the solum is the relatively unweathered parent material, termed substratum.
Spodosol: in Brazil, it is a class of mineral soil, hydromorphic or not, with a weak to moderate A horizon, and a Podzol B horizon, according to Camargo et al. (1987) nomenclature; or Spodic B horizon according to EMBRAPA (1999) nomenclature. In the USA Soil Taxonomy, it is related to the Spodosols ' Order.
Stereoscopy: optical device that allows three-dimensional (3-D) visualization of aerial photoimages .
Structure: soil structure is the arrangement of the solid parts of the soil, considering the aggregate types (platy, prismatic, columnar, granular, and blocky), sizes and development degree (large units are composed of smaller units separated by persistent planes of weakness).
Sum of bases (SB): is the sum of calcium, magnesium, potassium and sodium contents in the soil CEC (cation exchange capacity).
T
Texture: soil texture consists on the relative proportion of different grain sizes of mineral particles in a soil ( clay, silt and sand fractions).
Terrace (Fluvial): a fluvial terrace is the portion of a river valley lying adjacent to the floodplain.
V
Value (color): value is the soil color component that considers the black and white contribution. It is indicated in the Munsell Color Book in columns, varying from 0 (absolute black) as much as 10 (absolute white). In writing Munsell color notations, the sequence is always hue, value and chroma. In the example, 5 YR 4/3, the value is 4 (60% of black and 40% white).
W
Weathering:The destructive processes that change the physical and chemical characteristics of rocks and minerals at the earth's surface by means of chemical reactions such as hydration, hydrolysis, carbonation and oxidation.
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