Glossary of Soil Science Terms - Browse
B horizon Refer to soil horizon and Appendix II.
back-barrier beach A narrow, elongate, intertidal, sloping landform that is generally parallel with the shoreline located on the lagoon or estuary side of the barrier island, or spit (Subaqueous Soil Subcommittee, 2005). Compare barrier island.
back-barrier flat A subaerial, gently sloping landform on the lagoon side of the barrier beach ridge composed predominantly of sand washed over or through the beach ridge during tidal surges; a portion of a barrier flat (Subaqueous Soil Subcommittee, 2005). Compare washover-fan flat.
backbone what remains in the percolation cluster after the dead ends are removed (Hunt and Ewing, 2009).
backfurrow Refer to tillage, backfurrow.
backshore The upper or inner, usually dry, zone of the shore or beach, lying between the high-water line of mean spring tides and the upper limit of shore-zone processes; it is acted upon by waves or covered by water only during exceptionally severe storms or unusually high tides. It is essentially horizontal or slopes gently landward, and is divided from the foreshore by the crest of the most seaward berm ( Jackson, 1997). Compare washover fan.
backshore terrace (not preferred) Refer to berm.
backslope The hillslope position that forms the steepest, and generally linear, middle portion of the slope. In profile, backslopes are bounded by a convex shoulder above and a concave footslope below. They may or may not include cliff segments (i.e., free faces). Backslopes are commonly erosional forms produced by mass movement, colluvial action, and running water (Schoeneberger and Wysocki, personal communication, 2013; Hawley and Parsons, 1980). Compare summit, shoulder, footslope, toeslope.
backswamp A flood-plain landform. Extensive, marshy or swampy, depressed areas of flood plains between natural levees and valley sides or terraces (Hawley and Parsons, 1980).
backswamp deposit Laminated silt and clay deposited in the flood basin between valley sides or terraces and the natural levees of a river ( Jackson, 1997).
backwearing Slope erosion that causes the parallel retreat of an escarpment, slope of a hill or mountain, or the sideways recession of a slope without changing its general slope; a process contributing to the development of a pediment ( Jackson, 1997).
bacteriophage Virus that infects soil bacteria, often with desctruction or lysis of the host.
bacteroid An altered form of bacterial cells. Refers particularly to the swollen, irregular vacuolated cells of Rhizobium and Bradyrhizobium in legume nodules.
badland [soil survey] A miscellaneous area (map unit) applied to areas generally devoid of vegetation, intricately dissected by a fine, drainage network with a high drainage density, and have short, steep slopes with narrow interfluves resulting from erosion of soft geologic materials. Most common in arid or semiarid regions (USDA, 1993).
badlands [geomorphology] A landscape which is intricately dissected and characterized by a very fine drainage network with high drainage densities and short, steep slopes with narrow interfluves. Badlands develop on surfaces with little or no vegetative cover, overlying unconsolidated or poorly cemented materials (clays, silts, or in some cases sandstones) sometimes with soluble minerals such as gypsum or halite ( Jackson, 1997).
bajada (colloquial: southwestern USA) A broad, gently inclined, alluvial piedmont slope extending from the base of a mountain range out into a basin and formed by the lateral coalescence of a series of alluvial fans. Typically it has a broadly undulating transverse profile, parallel to the mountain front, resulting from the convexities of component fans. The term is generally restricted to constructional slopes of intermontane basins (Hawley and Parsons, 1980; Schoeneberger and Wysocki, personal communication, 2013). Synonym coalescent fan piedmont. Compare fan apron.
bald (not preferred; colloquial: southeastern USA; use summit, mountaintop, etc.) An ecological term for the grass or shrub covered (naturally tree-less) summit of a high elevation hill or mountain, flanked by forested slopes; not above the local tree-line ( Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013). Compare glade.
ballena (colloquial: western USA) A fan remnant having a distinctively rounded surface of fan alluvium. The ballena’s broadly rounded shoulders meet from either side to form a narrow summit and merge smoothly with concave side slopes and then concave, short pediments which form smoothly rounded drainageways between adjacent ballenas. A partial ballena is a fan remnant large enough to retain some relict fan surface on a remnant summit (Peterson, 1981; Schoeneberger and Wysocki, personal communication, 2013). Refer to fan remnant.
ballon (colloquial: western USA) A rounded, domeshaped hill, formed either by erosion or uplift ( Jackson, 1997).
band application Refer to banding.
banding A method of fertilizer or other agrichemical application above, below, or alongside the planted seed row. Refers to either placement of fertilizers close to the seed at planting or subsurface applications of solids or fluids in strips before or after planting. Synonym band application.
bank failure Process of erosion involving mass failure (e.g., earth topple) of a stream or gully bank.
bar [coast] A generic term for any of various elongate offshore ridges, banks, or mounds of sand, gravel, or other unconsolidated material submerged at least at high tide, and built up by the action of waves or currents, especially at the mouth of a river or estuary, or at a slight distance offshore from the beach ( Jackson, 1997). Compare longshore bar.
bar and channel topography A local-scale topographic pattern of recurring, small, sinuous or arcuate ridges separated by shallow troughs irregularly spaced across low-relief flood plains (slopes generally 2–6%); the effect is one of a subdued, sinuously undulating surface that is common on active, meandering flood plains. Micro-elevational differences between bars and channels generally range from <0.5 to 2 m and are largely controlled by the competency of the stream. The ridge-like bars often consist of somewhat coarser sediments compared to the finer textured sediments of the micro-low troughs (Schoenenberger and Wysocki, personal communication, 2013). Compare meander scroll, meander belt.
barchan dune A crescent-shaped dune with tips extending leeward (downwind), making this side concave and the windward (upwind) side convex. Barchan dunes tend to be arranged in chains extending in the dominant wind direction (Hawley and Parsons, 1980). Compare parabolic dune.
barrier beach [relict] (colloquial: western USA) A wide, gently sloping portion of a bolson floor comprising numerous, parallel, closely spaced, relict longshore-bars and lagoons built by a receding pluvial lake. Synonym offshore barrier, offshore beach, bar beach ( Jackson, 1997; Peterson, 1981). Refer to bar [coast], barrier island.
barrier island A long, narrow, sandy island, representing a broadened barrier beach that is above high tide and parallel to the shore, and that commonly has dunes, vegetated zones, and swampy or marshy terrains extending lagoonward from the beach. Also a long series of barrier beaches ( Jackson, 1997). Compare barrier beach.
barrier bar (not recommended) Use longshore bar.
barrier beach A narrow, elongate, coarse-textured, intertidal, sloping landform that is ridge rising slightly above high-tide level and generally parallel with the shore, but separated from it by a lagoon or marsh; it is rarely more than several kilometers long beach ridge component of a barrier island or spit and adjacent to the ocean (Subaqueous Soils Subcommittee, 2005). Refer to barrier island.
barrier cove A subaqueous area adjacent to a barrier island or submerged barrier beach that forms a minor embayment or cove within the larger basin (Subaqueous Soils Subcommittee, 2005). Compare cove, mainland cove.
barrier flat A relatively flat, low-lying area, often occupied by commonly including pools of water, separating the exposed or seaward edge of a barrier beach or barrier island from the lagoon behind it. An assemblage of both deflation flats left behind migrating dunes and/or storm washover sediments; may be either barren or vegetated (Subaqueous Soils Subcommittee, 2005; Jackson, 1997). Compare barrier beach, back-barrier flat.
barrow pit (not preferred) Use borrow pit.
basal till (a) (not preferred; obsolete, refer to subglacial till). Unconsolidated material of mixed composition deposited beneath a glacier and having a relatively high bulk density. [The term emphasizes only the relative position of deposition; i.e., subglacial till]. Types of basal till include lodgment, melt-out, and flow till ( Jackson, 1997; Schoenenberger and Wysocki, personal communication, 2013). (b) [obsolete use lodgment till]–A firm, dense, clay-rich till containing many abraded stones (coarse fragments) dragged along beneath a moving glacier and deposited upon bedrock or other glacial deposits ( Jackson, 1997).
basalt A fine-grained, basic igneous rock composed largely of pyroxene and calcium-rich plagioclase in about equal amounts.
base level The theoretical limit or lowest level toward which erosion of the Earth’s surface constantly progresses but seldom, if ever, reaches; especially the level below which a stream cannot erode its bed. The general or ultimate base level for the land surface is sea level, but higher temporary base levels may exist locally ( Jackson, 1997).
base saturation The ratio of the quantity of exchangeable bases to the cation-exchange capacity. The value of the base saturation varies according to whether the cation exchange capacity includes only the salt extractable acidity (refer to cation exchange capacity) or the total acidity determined at pH 7 or 8. Generally expressed as a percentage. [Note: Base saturation varies with the pH at which it is measured].
base slope [geomorphology] A geomorphic component of hills consisting of the concave to linear slope (perpendicular to the contour) which, regardless of the lateral shape, is an area that forms an apron or wedge at the bottom of a hillside dominated by colluvial and slope wash processes and sediments (e.g., colluvium and slope alluvium). Distal base slope sediments commonly grade to, or interfinger with, alluvial fills, or gradually thin to form pedisediment over residuum. Compare head slope, side slope, nose slope, interfluve, free face (Schoenenberger and Wysocki, personal communication, 2013).
baseflow That part of stream flow derived from groundwater seeping into the stream from the adjoining water table with delayed response to storms.
basic fertilizer One that, after application to and reaction with soil, decreases residual acidity and increases soil pH.
basic slag A by-product in the manufacture of steel, containing lime, phosphorus, and small amounts of other plant nutrients such as sulfur, manganese, and iron.
basin (a) Drainage basin; (b) A low area in the Earth’s crust, of tectonic origin, in which sediments have accumulated ( Jackson, 1997). (c) (colloquial: western USA) A general term for the nearly level to gently sloping, bottom surface of an intermontane basin (bolson). Landforms include playas, broad alluvial flats containing ephemeral drainageways, and relict alluvial and lacustrine surfaces that rarely, if ever, are subject to flooding. Where through-drainage systems are well developed, flood plains are dominant and lake plains are absent or of limited extent. Basin floors grade mountainward to distal parts of piedmont slopes (Peterson, 1981).
basin floor A general term for the nearly level, lower-most part of intermontane basins (i.e., bolsons, semi-bolsons). The floor includes all of the alluvial, eolian, and erosional landforms below the piedmont slope. Compare basin, piedmont slope (Peterson, 1981).
basin-floor remnant (colloquial: western USA) A relatively flat, erosional remnant of any former landform of a basin floor that has been dissected following the incision of an axial stream (Peterson, 1981).
batch culture A method for culturing organisms in which the organism and supporting nutritive medium are added to a closed system. Compare chemostat.
batholith
A large, generally discordant plutonic rock body exposed at the land surface, with an aerial extent > 40 sq. mi. (100 km2) and no known bottom (e.g., Idaho batholith; Jackson, 1997; Schoenenberger and Wysocki, personal communication, 2013). Compare stock.
bauxite An off-white to dark red brown weathered detritus or rock composed of aluminum oxides (mainly gibbsite with some boehmite and diaspore), iron hydroxides, silica, silt, and especially clay minerals. Bauxite originates in tropical and subtropical environments as highly weathered residue from carbonate or silicate rocks and can occur in concretionary, earthy, pisolitic or oolitic forms ( Jackson, 1997; Schoenenberger and Wysocki, personal communication, 2013).
bay [coast] (a) A wide, curving open indentation, recess, or arm of a sea (e.g., Chesapeake Bay) or lake (e.g., Green Bay, WI) into the land or between two capes or headlands, larger than a cove [coast], and usually smaller than, but of the same general character as, a gulf. (b) A large tract of water that penetrates into the land and around which the land forms a broad curve. By international agreement a bay is a water body having a baymouth that is less than 24 nautical miles wide and an area that is equal to or greater than the area of a semicircle whose diameter is equal to the width of the bay mouth ( Jackson, 1997). Compare gulf.
bay bottom The nearly level or slightly undulating central portion of a submerged, low-energy, depositional estuarine embayment characterized by relatively deep water (1.0 to >2.5 m; Subaquesous Soils Subcommittee, 2005). Compare lagoon bottom.
bayou A term applied to many local water features in the lower Mississippi River basin and in the Gulf Coast region of the USA. Its general meaning is a creek or secondary watercourse that is tributary to another body of water; especially a sluggish and stagnant stream that follows a winding course through alluvial lowlands, coastal swamps or river deltas ( Jackson, 1997). Compare oxbow, slough.
beach (a) (landform) A gently sloping zone of unconsolidated material, typically with a slightly concave profile, extending landward from the low-water line to the place where there is a definite change in material or physiographic form (e.g., a cliff), or to the line of permanent vegetation (usually the effective limit of the highest storm waves); a shore of a body of water, formed and washed by waves or tides, usually covered by sand or gravel. (b) (material) the relatively thick and temporary accumulation of loose water-borne material (usually well-sorted sand and pebbles) accompanied by mud, cobbles, boulders, and smoothed rock and shell fragments, that is in active transit along, or deposited on, the shore zone between the limits of low water and high water ( Jackson, 1997). Compare beach sand.
beach plain A continuous and level or undulating area formed by closely spaced successive embankments of wave-deposited beach material added more or less uniformly to a prograding shoreline, such as to a growing compound spit or to a cuspate foreland ( Jackson, 1997). Compare wave-built terrace, chenier plain.
beach ridge A low, essentially continuous mound of beach or beach-and-dune material heaped up by the action of waves and currents on the backshore of a beach, beyond the present limit of storm waves or the reach of ordinary tides, and occurring singly or as one of a series of approximately parallel deposits. The ridges are roughly parallel to the shoreline and represent successive positions of an advancing shoreline. ( Jackson, 1997).
beach sands [soil survey] Well sorted, sand-sized, clastic material transported, deposited primarily by wave action and deposited in a shore environment. Compare eolian sands (Schoenenberger and Wysocki, personal communication, 2013).
beach terrace (a) A landform that consists of a wavecut scarp and wave-built terrace of well-sorted sand and gravel of marine and lacustrine origin. (b) (colloquial: western USA) relict shorelines from pluvial lakes, generally restricted to valley sides (Peterson, 1981). Compare strandline, shoreline.
beaches [soil survey] A miscellaneous are (map unit) applied to areas of sandy, gravelly, or cobbly shores actively reworked by waves (commonly at least partly covered with water during high tides or storms (USDA, 1993).
beaded stream pattern A characteristic pattern of small streams in areas underlain by ice wedges. The course of the stream channel is controlled by the pattern of the wedges, with beads (pools) occurring at the junctions of the wedges (National Research Council of Canada, 1988).
beaded drainage pattern (not recommended; refer to beaded stream pattern.)
bed [agronomy] A raised (usually) cultivated area between furrows or wheel tracks of tractors that is specially prepared, managed and/or irrigated to promote the production of a planted crop.
bed load Refer to erosion, bed load.
bed planting Refer to tillage, bed planting.
bed shaper Refer to tillage, bed shaper.
bedded Formed, arranged, or deposited in layers or beds, or made up of or occurring in the form of beds; especially said of a layered sedimentary rock, deposit, or formation ( Jackson, 1997).
bedding Refer to tillage, bedding.
bedding plane A planar or nearly planar bedding surface that visibly separates each successive layer of stratified sediment or rock (of the same or different lithology) from the preceding or following layer; a plane of deposition. It often marks a change in the circumstances of deposition, and may show a parting, a color difference, a change in particle size, or various combinations. A term commonly applied to any bedding surface even when conspicuously bent or deformed by folding ( Jackson, 1997; Schoenenberger and Wysocki, personal communication, 2013).
bedrock A general term for the solid rock that underlies the soil and other unconsolidated material or that is exposed at the surface ( Jackson, 1997). Compare regolith, residuum.
beidellite A dioctahedral smectite with the majority of the charge originating in the tetrahedral layer.
bench (not preferred) Use structural bench.
bentonite A relatively soft rock formed by chemical alteration of glassy, high silica (acidic) content volcanic ash. This material shows extensive swelling in water and has a high specific surface area. The principal mineral constituent is clay-size smectite.
berm [beach] A low, impermanent, nearly horizontal or landward-sloping shelf, ledge, or narrow terrace on the backshore of a beach, formed of material thrown up and deposited by storm waves; it is generally bounded on one side or the other by a beach ridge or beach scarp. Some beaches have no berms, others have one or several ( Jackson, 1997).
Bernoulli’s Principal The soil water potential decreases in the direction of flow.
beryl
A berllium aluminum silicate mineral containing Si6O18–12 rings.
beveled base The lower portion of a canyon wall or escarpment marked by a sharp reduction in slope gradient from the precipitous cliff above, and characteristically composed of thinly mantled colluvium (e.g., <1 m) and/ or carapaced with a thin surficial mantle of large rock fragments from above, which overly residuum of less resistant rock (e.g., shale) whose thin strata intermittently outcrop at the surface; a zone of erosion and transport common in the canyonlands of the semi-arid, southwestern USA (Schoenenberger and Wysocki, personal communication, 2013). Compare talus slope.
beveled cut A bank or slope portion of a cut excavated into unconsolidated material (regolith) or bedrock as in a roadcut, whose slope gradient has been mechanically reduced to a subdued angle (e.g., to <33%) to increase slope stability, reduce erosion, or to facilitate revegetation (Schoenenberger and Wysocki, personal communication, 2013). Compare cut, cutbank, roadcut.
bioassay A method for quantitatively measuring a substance by its effect on the growth of a suitable microorganism, plant, or animal under controlled conditions.
biodegradable A substance able to be decomposed by biological processes.
biofertilizer Mixture of selected beneficial microorganisms and/or other organic substances (i.e., growth hormones, vitamins, etc.) for sustainable soil management and plant productivity.
biofilm Organized microbial systems consisting of layers of microbial cells attached to surfaces, with complex structural (i.e., extracellular polysacchrides) and functional (i.e., anaerobic degradion) characteristics; can form on roots, organic residues, and water pipes, for example.
biological immobilization Refer to immobilization, biological interchange.
biological availability That portion of a chemical compound or element that can be taken up readily by living organisms.
biological denitrification Refer to denitrification.
biological interchange The interchange of elements between organic and inorganic states in a soil or other substrate through the action of living organisms. It results from the biological decomposition of organic compounds with the liberation of inorganic materials (mineralization) and the utilization of inorganic materials with synthesis of microbial tissue (immobilization).
biomass (a) The total mass of living organisms in a given volume or mass of soil. (b) The total weight of all organisms in a particular environment. Compare microbial biomass.
biopore A macropore in the soil due to activity of roots or mesoor macrofauna.
bioremediation The use of biological agents to reclaim soil and water polluted by substances hazardous to the environment or human health.
biosequence A group of related soils that differ, one from the other, primarily because of differences in kinds and numbers of plants and soil organisms as a soil-forming factor.
biostimulation Addition of nutrients to contaminated soil to stimulate indigenous microorganisms to carry out bioremediation.
bioswale An artificially constructed or modified, closed or semi-open basin or drainageway designed to capture storm water runoff primarily from impervious surfaces (e.g., parking lots, roofs) and to maximize onsite infiltration in order to reduce runoff, to improve water quality by soil filtration, and to recharge local ground (Schoenenberger and Wysocki, personal communication, 2013).
biotechnology Use of living organisms, often soil microorganisms, to carry out defined physiochemical processes having agricultural or industrial application.
biotic enzymes Enzymes associated with viable proliferating cells located (i) intracellularly in cell protoplasm; (ii) in the periplasmic space; and (iii) at the outer cell surfaces.
biotite A brown, trioctahedral layer silicate of the mica group with Fe(II) and Mg in the octahedral layer and Si and Al in a ratio of 3:1 in the tetrahedral layer. Compare Appendix I, Table A3.
birefringence The numerical difference between the highest and lowest refractive index of a mineral. Minerals with birefringence exhibit interference colors in thin section or grain mounts when viewed in crossed-polarized light.
birnessite (Na0.7Ca0.3)Mn7O14 • 2.8H2O A black manganese oxide that is common in iron-manganese nodules of soils and cutans. It has a layer structure.
bisect A profile of plants and soil showing the vertical and lateral distribution of roots and tops in their natural position.
bisequal Soils in which two sequa have formed, one above the other, in the same deposit.
biuret
H2NCONHCONH2A product formed at high temperature during the manufacturing of urea. It is toxic to plants. Synonym carbamoylurea.
Black Earth [Soil Class.] A term used by some as synonymous with “Chernozem”; used by others (e.g., Australia) to describe self-mulching black clays (Not used in soil taxonomy).
Black Soils [Canadian Soil Class.] Soils with dark-colored surface horizons of the black (Chernozem) zone; includes Black Earth or Chernozem, Wiesenboden, Solonetz, etc. (Not used in soil taxonomy.)
bleicherde The light-colored, leached A2(E) horizon of Podzol soils (Not used in U.S. soil taxonomy).
blind valley A valley, commonly in karst, that ends abruptly downstream at the point at which its stream disappears underground ( Jackson, 1997).
block stream An accumulation of boulders or angular blocks, with no fine sizes in the upper part, overlying solid or weathered bedrock, colluvium, or alluvium, and lying below a cliff or ledge from which coarse fragments originate. Block streams usually occur 2 2 at the heads of ravines as narrow bodies that are more 2 2 at the heads of ravines as narrow bodies that are more temperature during the manufacturing of urea. It is toxic to plants. Synonym carbamoylurea.
block checking Refer to tillage, block.
block field A thin accumulation of stone blocks, typically angular, with only coarse fragments in the upper part, over solid or weathered bedrock, colluvium, or alluvium, without a cliff or ledge above as an apparent source. Block fields occur on high mountain slopes above tree-line, or in polar or paleo-periglacial regions; they are most extensive along slopes parallel to the contour; and they generally occur on slopes of <5% ( Jackson, 1997). Synonym felsenmeer. Compare block stream, talus, scree. extensive downslope than along the slope. They may exist on any slope angle, but ordinarily not steeper than 90 percent slope (approx. 40 degrees; Jackson, 1997). Compare block field.
block glide [mass movement] The process, associated sediments (block glide deposit) or resultant landform characterized by a slow type of slide, in which largely intact units (blocks) of rock or soil slide downslope along a relatively planar surface, such as a bedding plane, without any significant distortion of the original mass; a type of translational slide (Schoenenberger and Wysocki, personal communication, 2013; Varnes, 1978). Compare rotational landslide, debris slide, lateral spread, landslide.
block lava Lava having a surface of angular blocks; it is similar to a a lava but the fragments are larger and more regular in shape, somewhat smoother, and less vesicular ( Jackson, 1997). Compare a a lava, pahoehoe lava, pillow lava.
block lava flow A lava flow dominated by block lava (Schoenenberger and Wysocki, personal communication, 2013). Compare a a lava flow, pahoehoe lava flow, pillow lava flow.
block thinning Refer to tillage, block.
block [volcanic] A pyroclast that was ejected in a solid state; it has a diameter greater than 64 mm. Compare bomb, cinder, lapilli, tephra ( Jackson, 1997).
blocky soil structure A type of soil structure. Compare soil structure and soil structure types.
blown-out land [soil survey] A miscellaneous area (map)-unit from which most of the soil has been removed by wind erosion. The areas are generally shallow depressions with flat, irregular floors, which in some instances have a layer of pebbles or cobbles (USDA, 1993).
blowout A hollow saucer-, cup-, or trough-shaped depression of the land surface, formed by wind erosion especially in an area of shifting sand, loose soil, or where vegetation is disturbed or destroyed; the adjoining accumulation of sand derived from the depression, where recognizable, is commonly included. Commonly small, some blowouts may be large (kilometers in diameter; Jackson, 1997). Compare deflation basin.
blue rock
[volcanic] (colloquial – Hawaii) The very dense (e.g., 2.75 g cm-1), extremely hard and massive, nominally vesicular lava that commonly forms the inner core of an a a lava flow (Schoenenberger and Wysocki, personal communication, 2013).
bluff (a) A high bank or bold headland, with a broad, precipitous, sometimes rounded cliff face overlooking a plain or body of water, especially on the outside of a stream meander; e.g., a river bluff. (b) (not preferred) use cliff. Any cliff with a steep, broad face ( Jackson, 1997). temperature during the manufacturing of urea. It is toxic to plants. Synonym carbamoylurea.
BOD (biochemical oxygen demand) The quantity of oxygen used in the biochemical oxidation of organic and inorganic matter in a specified time, at a specified temperature, and in specified conditions. An indirect measure of the concentration of biologically degradable material present in organic wastes.
bog An organic-accumulating wetland that has no significant inflows or outflows and supports acidophilic mosses, particularly Sphagnum. Compare fen, marsh, pocosin, swamp, and wetland.
bog iron ore Impure ferruginous deposits developed in bogs or swamps by the chemical or biochemical oxidation of iron carried in solution.
Bog soil [soil classification](obsolete; not used in soil taxonomy.) A great soil group of the intrazonal order and hydromorphic suborder. Includes muck and peat. (Baldwin et al., 1938)
bolson (colloquial: western USA.) A landscape term applied to for an internally drained (closed) intermontane basin in arid regions where into which drainages from surroundingadjacent mountains converge inward toward a central depression. Bolsons are often tectonically formed depressions, depressed areas and, according to Peterson (1981), a bolson can include alluvial flat, alluvial plain, beach plain, barrier beach, lake plain, sand sheets, dunes, and playa landforms. The piedmont slope above a bolson includes slopes of erosional surfaces origin adjoining the mountain front (pediments) and complex older depositional surfaces construction surfaces (fans) that adjoin the mountain front. A semi-bolson is an externally drained (open) bolson (Schoenenberger and Wysocki, personal communication, 2013; Jackson, 1997). Synonym intermontane basin.
bomb [volcanic] A pyroclast > 64 mm in at least one dimension that was ejected while still viscous and solidified into it’s rounded form in flight ( Jackson, 1997). Compare block, cinder, lapilli, tephra.
boom Refer to irrigation, sprinkler irrigation systems terms: boom.
boom side-move sprinkler Refer to irrigation, sprinkler irrigation systems terms: boom, side-move sprinkler.
boom sprinkler distribution pattern Refer to irrigation, sprinkler irrigation systems terms:, boom, sprinkler distribution pattern.
boom center pivot Refer to irrigation, sprinkler irrigation systems terms: boom, center pivot.
boom corner pivot Refer to irrigation, sprinkler irrigation systems terms: boom, corner pivot.
boom lateral move Refer to irrigation, sprinkler irrigation systems terms: boom, lateral move.
boom microirrigation Refer to irrigation, sprinkler irrigation systems terms, boom, microirrigation.
boom mist irrigation Refer to irrigation, sprinkler irrigation systems terms: boom, mist irrigation.
boom nozzle Refer to irrigation, sprinkler irrigation systems terms, boom, nozzle.
boom side-roll sprinkler Refer to irrigation, sprinkler irrigation systems terms: boom, side-roll sprinkler.
boom towed sprinkler Refer to irrigation, sprinkler irrigation systems terms: boom, towed sprinkler.
Boralfs [soil taxonomy] (obsolete; not used in current soil taxonomy) Prior to 1999 this was a suborder of Alfisols that have formed in cool places. Boralfs have frigid or cryic but not pergelic temperature regimes, and have udic moisture regimes. Boralfs are not saturated with water for periods long enough to limit their use for most crops (USDA, 1999; Appendix I).
border dikes Refer to irrigation, border dikes.
border ditch Refer to irrigation, border ditch.
border-strip Refer to irrigation, border-strip.
Borolls
[soil taxonomy] (obsolete; not used in current soil taxonomy) Prior to 1999 this was a suborder of Mollisols with a mean annual soil temperature of <8°C that are never dry for 60 consecutive days or more within the 90 days following the summer solstice. Borolls do not contain material that has a CaCO3 equivalent >400 g kg-1 unless they have a calcic horizon, and they are not saturated with water for periods long enough to limit their use for most crops (USDA, 1999; Appendix I).
borrow pit An excavated area from which earthy material has been removed typically for construction purposes offsite; also called barrow pit ( Jackson, 1997).
bottomland (obsolete; use flood plain). An informal term, loosely applied to varying portions of a flood plain.
boulder field (not recommended) use block stream. Compare block field.
boulders Rock or mineral fragments >600 mm in diameter. Compare rock fragments.
bouldery Containing appreciable quantities of boulders. Compare rock fragments.
bouyance The upward force acting on a particle because it is suspended in water.
bowl [gilgai] A cup-or trough-shaped subsurface feature centered under and surrounding the microlow of a gilgai, commonly 3 to 5 m across and 1.5 to 3 m thick, containing numerous slickensides (oblique slip/shear faces) within it and bounded at its base by master slickensides. A bowl contains turbated material produced in soils containing substantial smectitic clay (e.g., Vertisols). Bowl morphology is distinct from that in adjacent microhighs (chimney) and underlying horizons. Substratum morphology is not preserved within the bowl. Compare chimney [gilgai], intermediate position [gilgai], gilgai (Schoenenberger and Wysocki, personal communication, 2013).
box canyon (a) A narrow gorge or canyon containing an intermittent stream following a zigzag course, characterized by high, steep rock walls and typically closed upstream by a similar wall, giving the impression, as viewed from its bottom, of being surrounded or “boxed in” by almost vertical walls. (b) A steep-walled canyon heading against a cliff a dead-end canyon ( Jackson, 1997).
bradyrhizobia Collective common name for the genus Bradyhizobium. Compare rhizobia.
Bragg's law The relationship between x-ray wavelength (λ), the crystal planar spacings (d), and the x-ray beam incident angle (θ) when diffraction occurs; nλ = 2dsinθ.
braided channel (not recommended) Use braided stream.
braided stream A channel or stream with multiple channels that interweave as a result of repeated bifurcation and convergence of flow around interchannel bars, resembling (in plan view) the strands of a complex braid. Braiding is generally confined to broad, shallow streams of low sinuosity, high bedload, noncohesive bank material, and a steep gradient. At a given bank-full discharge, braided streams have steeper slopes and shallower, broader, and less stable channel cross sections than meandering streams. Compare meandering channel, floodplain landforms (Hawley and Parsons, 1980).
breached anticline A structurally controlled landscape or landform typically underlain by sedimentary rocks in which an anticline crest has been eroded such that the former crest has become a canyon or valley flanked by inward-facing erosional scarp slopes or cliffs and outward-facing dip slopes. Associated landforms include cuestas and strike valleys ( Jackson, 1997; Schoenenberger and Wysocki, personal communication, 2013).
break [slopes] An abrupt change or inflection in a slope or profile. Compare knickpoint, shoulder, escarpment. (geomorphology) A marked variation of topography, or a tract of land distinct from adjacent land, or an irregular or rough piece of ground ( Jackson, 1997). Compare breaks.
breaklands An assemblage of very steep (e.g., 60–90%), high relief slopes flanking major rivers and streams in mountainous terrain that form the walls of a v-shaped river valley. Breaklands are characterized by colluviated slopes of which the majority of the ground surface drains directly to a large axial stream at the base, and the remainder consists of shallowly incised, parallel drainageways. Breaklands have shallow to very deep soils, substantial rock outcrop, and have more frequent fires than lower gradient mountain slopes above; extensive along the rivers and streams of the Idaho Batholith (Holdorf and Donahue, 1990; Schoenenberger and Wysocki, personal communication, 2013). Compare dissected breaklands.
breaks (colloquial: western USA) A landscape or large tract of steep, rough or broken land dissected by ravines and gullies and marks a sudden change in topography as from an elevated plain to lower hilly terrain, or a line of irregular cliffs at the edge of a mesa or a river (e.g., the Missouri River breaks; Jackson, 1997; Schoenenberger and Wysocki, personal communication, 2013).
breakthrough curve The relative solute concentration in the outflow from a column of soil or porous medium after a step change in solute concentration has been applied to the inlet end of the column, plotted against the volume of outflow (often in number of pore volumes).
breakthrough time (tb) The time at which the center of mass of a solute reaches the soil column outlet.
breccia A coarse-grained, clastic rock composed of angular fragments (>2 mm) bonded by a mineral cement or in a finer-grained matrix of varying composition and origin. The consolidated equivalent of rubble. Compare conglomerate.
broad interstream divide (colloquial: southeastern USA) A type of very wide, low gradient (level to nearly level) interfluve that lacks a well developed drainage network such that large portions of the local upland lack stream channels or other drainageways; extensive in lower coastal plains and some lake plains, till plains and alluvial plain remnants. Compare interfluve (Raymond Daniels, personal communication, 1993; Schoenenberger and Wysocki, personal communication, 2013).
broadcast The application of solid or liquid fertilizer or other agrichemical on the soil surface. Usually done prior to planting and normally incorporated with tillage, but may be unincorporated in no-till systems.
broadcast application The application of material scattered or sprayed on surface of the soil.
broadcast planting Refer to tillage, broadcast planting.
brook [streams](not preferred, use ephemeral stream) Generally a very small, ephemeral stream, especially one that issues from a spring or seep and conducts less water volume and over shorter distances than a creek. Compare intermittent stream ( Jackson, 1997).
Brown Earths [soil classification](obsolete; not used in soil taxonomy) Soils with a mull horizon but having no horizon of accumulation of clay or sesquioxides (Baldwin et al., 1938).
Brown Forest soils [soil classification] (obsolete; not used in soil taxonomy) A great soil group of the intrazonal order and calcimorphic suborder, formed on calcium-rich parent materials under deciduous forest, and possessing a high base status but lacking a pronounced illuvial horizon (Baldwin et al., 1938).
Brown Podzolic soils [soil classification] (obsolete; not used in soil taxonomy) A zonal great soil group similar to Podzols but lacking the distinct A2 (E) horizon characteristic of the Podzol group (Baldwin et al., 1938).
Brown soils [soil classification] (obsolete; not used in soil taxonomy) A great soil group of the temperate to cool arid regions, composed of soils with a brown surface and a light-colored transitional subsurface horizon over calcium carbonate accumulation (Baldwin et al., 1938).
brucite
The mineral Mg(OH)2; it has a layer type structure with magnesium ions in octahedral coordination and is the structure model for the trioctahedralsheet in layer silicates.
Brunizem [soil classification] (obsolete; not used in soil taxonomy). A zonal great soil group consisting of soils formed under temperate to cool-temperate, humid regions under tall grass vegetation (Baldwin, et al., 1938). Synonym Prairie soils.
bubbling pressure Refer to air-entry value.
buffer power The ability of solid phase soil materials to resist changes in ion concentration in the solution phase. Can be expressed as ∂Cs/∂Cl where Cs represents the concentration of ions on the solid phase in equilibrium with Cl, the concentration of ions in the solution phase. Includes pH buffering as well as the buffering of other ionic and molecular components.
bulk blending Mixing dry, individually granulated materials to form a mixed fertilizer.
bulk area The total area, including solid particles and pores, of a cross-section through an arbitrary quantity of soil; the area counterpart of bulk volume.
bulk density, soil
(ρb or Db) The mass of dry soil per unit bulk volume. The value is expressed as megagram per cubic meter, Mg m-3.
bulk fertilizer Solid or liquid fertilizer in a non-packaged form.
bulk length The total length, including solid particles and pores, of a straight-line path through the soil; the length counterpart of bulk volume or bulk area.
bulk specific gravity (no longer used in SSSA publications) The ratio of the mass of a unit volume of dry soil to the mass of the same unit volume of water.
bulk volume The volume, including the solids and the pores, of an arbitrary soil mass. The bulk volume is determined before drying to constant weight at 105°C.
burial mound A human-made pile, hillock or hill, composed of debris or earth heaped up to mark a burial site (International Committee of Anthropogenic Soils, 2013; Jackson, 1997).
buried (adjective) Landforms, geomorphic surfaces, or paleosols covered by younger sediments (e.g., eolian, glacial, and alluvial). Compare exhumed, relict (Hawley and Parsons, 1980).
buried soil Soil covered by an alluvial, loessal, or other earthy mantle of more recent depositional material, usually to a depth greater than 50 cm; recent surface deposits < 50 cm thick are generally considered as part of the ground soil. Refer to ground soil, exhumed, relict (Soil Survey Staff, 1978).
burying Refer to tillage, burying.
butte An isolated, generally flat-topped hill or mountain with relatively steep slopes and talus or precipitous cliffs and characterized by summit width that is less than the height of bounding escarpments, commonly topped by a caprock of resistant material and representing an erosion remnant carved from flat-lying rocks. Compare mesa, plateau, cuesta (Hawley and Pasons, 1980; Jackson, 1997).
bypass flow Rapid flow of water around solutes in the immobile soil matrix.