Glossary of Soil Science Terms - Browse
fabric The physical constitution of soil material as expressed by the spatial arrangement of the solid particles and associated voids.
faceted spur The inverted V-shaped end of a ridge that has been truncated or steeply beveled by steam erosion (e.g., meander scar or bluff), glacial truncation, or fault scarp displacement (Schoeneberger and Wysocki, personal communication, 2013). Compare spur.
facies [stratigraphy] A distinctive group of characteristics that distinguish one group from another within a stratigraphic unit; the sum of all primary lithologic and paleontologic characteristics of sediments or sedimentary rock that are used to infer its origin and environment; the general nature of appearance of sediments or sedimentary rock produced under a given set of conditions; a distinctive group of characteristics that distinguishes one group from another within a stratigraphic unit; e.g., contrasting river-channel facies and overbank-flood-plain facies in alluvial valley fills.
facultative organism An organism that can carry out both options of a mutually exclusive process (e.g., aerobic and anaerobic metabolism). May also be used in reference to other processes, such as photosynthesis (e.g., a facultative photosynthetic organism is one that can use either light or the oxidation of organic or inorganic compounds as a source of energy).
faecal (fecal) pellets Rounded and subrounded aggregates of fecal material produced by the soil fauna. adsorption complex of a soil is occupied by a particularcation. It is expressed as:ECP = {[exchangeable cation (cm kg soil)]/[cation exchange capacity (cm kg soil)]}100.
fall [mass movement] A category of mass movement processes, associated sediments (fall deposit), or resultant landforms (e.g., rockfall, debris fall, soil fall) characterized by very rapid movement of a mass of rock or earth that travels mostly through the air by free fall, leaping, bounding, or rolling, with little or no interaction between one moving unit and another. Compare topple, slide, lateral spread, flow, complex landslide, landslide (Schoeneberger and Wysocki, personal communication, 2013; Varnes, 1978).
fall cone A variety of cone penetrometer that utilizes dropping weights to provide known increments of force applied to the cone, resulting in measured increments of soil penetration.
fall line (not recommended; obsolete) An imaginary line or narrow zone connecting the water falls on several adjacent or near-parallel rivers, marking the points where these rivers make a sudden descent from an upland to a lowland, as at the edge of a plateau; specifically, the Fall Line marking the boundaries between the ancient, resistant crystalline rocks of the Piedmont Plateau and the younger, softer sediments of the Atlantic Coastal Plain of the Eastern United States. It also marks the limit of navigability of the rivers. Now considered an archaic term because Coastal Plain materials occur several miles west or inland of the Fall Line and current research is showing it to be a broad zone of high-angle reverse faults ( Jackson, 1997).
falling dune An accumulation of sand that is formed as sand is blown off a mesa top or over a cliff face or steep slope, forming a solid wall, sloping at the angle of repose of dry sand, or a fan extending downward from a re-entrant in the mesa wall. Compare climbing dune, sand ramp ( Jackson, 1997).
fallow Refer to tillage, fallow.
family, soil [soil taxonomy] An intermediate category between the subgroup and the soil series. Families provide groupings of soils with ranges in texture, mineralogy, temperature, and thickness (USDA, 1999). Compare classification, soil.
fan [geomorphology] (a) A gently sloping, fan-shaped mass of detritus forming a section of a low-angle cone commonly at a place where there is a notable decrease in gradient; specifically an alluvial fan (not preferred – use alluvial fan). Refer to alluvial fan, alluvial cone. (b) A fan-shaped mass of congealed lava that formed on a steep slope by the continually changing direction of flow ( Jackson, 1997).
fan apron A sheet-like mantle of relatively young alluvium and soils covering part of an older fan piedmont (and occasionally alluvial fan) surface, commonly thicker and further down slope (e.g., mid-fan or midfan piedmont) than a fan collar. It somewhere buries an older soil that can be traced to the edge of the fan apron where the older soil emerges as the land surface, or relict soil. No buried soils should occur within a fan-apron mantle itself (Peterson, 1981). Compare fan collar.
fan collar A landform comprised of a thin, short, relatively young mantle of alluvium along the very upper margin (near the proximal end or apex) of a major alluvial fan. The young mantle somewhere buries an older soil that can be traced to the edge of the collar where the older soil emerges at the land surface as a relict soil (Peterson, 1981). Compare fan apron.
fan piedmont The most extensive landform on piedmont slopes, formed by (i) the lateral, downslope, coalescence of mountain-front alluvial fans into one generally smooth slope with or without the transverse undulations of the semi-conical alluvial fans, and (ii) accretions of fan aprons (Peterson, 1981).
fan remnant A general term for landforms that are the remaining parts of older fan-landforms, such as alluvial fans, fan aprons, inset fans, and fan skirts, that either have been dissected (erosional fan-remnants) or partially buried (nonburied fan-remnants). An erosional fan remnant must have a relatively flat summit that is a relict fan-surface. A nonburied fan-remnant is a relict surface in its entirety. Compare eroded fan remnant, ballena (Peterson, 1981).
fan remnant sideslope (not preferred) Use eroded fan-remnant sideslope.
fan skirt The zone of smooth, laterally-coalescing, small alluvial fans that issue from gullies cut into the fan piedmont of a basin or that are coalescing extensions of the inset fans of the fan piedmont, and that merge with the basin floor at their toeslopes. These are generally younger fans which onlap older fan surfaces (Peterson, 1981).
fan terrace (not preferred) Use fan remnant.
fanglomerate
A sedimentary rock consisting of waterworn, heterogeneous fragments of all sizes, deposited in an alluvial fan and later cemented into a firm rock (Jackson, 1997).
fanhead trench A linear depression formed by a drainageway that is incised considerably below the surface of an alluvial fan ( Jackson, 1997).
fault A descrete surface (fracture) or fracture zone of the earth with displacement along one side in respect to the other.
fault block A displaced crustal unit, formed during block faulting, that is bounded by faults, either completely or in part, and behaves as a coherent unit during tectonic activity. Compare fault-block mountain (Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997).
fault line The trace of a fault plane on the ground surface or on a reference plane. Compare fault zone, faultline scarp ( Jackson, 1997).
fault zone A fault that is expressed as a zone of numerous small fractures or of breccia or fault gouge. A fault zone may be as wide as hundreds of meters. Compare fault, fault-scarp ( Jackson, 1997).
fault-block mountains Mountains that formed primarily by block faulting, and commonly exhibit asymmetrical rotation and vertical displacement from a horizontal plane by large, coherent fault-block units hinged along fault lines; common in, but not limited to, the Basin and Range region of the USA. The term is not applied to mountains formed by thrust-faulting (Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997).
fault-line scarp (a) A steep slope or cliff formed by differential erosion along a fault line, as by the more rapid erosion of soft rock on the side of a fault as compared to that of more resistant rock on the other side; e.g., the east face of the Sierra Nevada in California. (b) (not recommended) A fault scarp that has been modified by erosion. This usage is not recommended because the scarp is usually not located on the fault line ( Jackson, 1997).
felsenmeer
Use block field (Jackson, 1997).
felsic rock
A general term for igneous rock containing abundant, light-colored minerals (granite, etc.); also applied to those minerals (quartz, feldspars, feldspathoids, muscovite) as a group. Compare mafic rock (Jackson, 1997).
fen A peat accumulating wetland that receives some drainage from surrounding mineral soils and usually supports marshlike vegetation. These areas are richer in nutrients and less acidic than bogs. The soils under fens are peat (Histosols) if the fen has been present for a while. Compare bog, pocosin, swamp, and wetland.
fenster (not preferred) Use window.
fermentation The metabolic process in which an organic compound serves as both an electron donor and the final electron acceptor.
ferran A cutan composed of iron oxides, hydroxides, or oxyhydroxides.
ferri-argillan A cutan consisting of a mixture of clay minerals and iron oxides, hydroxides, or oxyhydroxides.
ferrihydrite Fe5O7(OH) •4H2O. A dark reddish-brown, poorly crystalline iron oxide mineral that forms in wet soils. Occurs in concretions and placic horizons and often can be found in ditches and pipes that drain wet soils.
Ferrods [Soil Tax.] (obsolete) Prior to 1999, this was a suborder of Spodosols that have more than six times as much free iron (elemental) than organic carbon in the spodic horizon. Ferrods are rarely saturated with water or do not have characteristics associated with wetness (USDA, 1999; Appendix I).
ferrolysis Clay destruction process involving disintegration and solution in water based upon the alternate reduction and oxidation of iron.
fertigation Application of plant nutrients in irrigation water.
fertility, soil The relative ability of a soil to supply the nutrients essential to plant growth.
fertilization, foliar Application of a dilute solution of liquid fertilizers to plant foliage.
fertilizer
Any organic or inorganic material of natural or synthetic origin (other than liming materials) that is added to a soil to supply one or more plant nutrients essential to the growth of plants.
fertilizer analysis
The percentage composition of a fertilizer as determined in a laboratory and expressed as total N, available phosphoric acid (P2O5) equivalent, and water-soluble potash (K2O) equivalent.
fertilizer fixation Refer to fixation.
fertilizer grade The guaranteed minimum analysis in percent of the major plant nutrient elements contained in a fertilizer material or in a mixed fertilizer. The analysis is usually designated as N–P2O5–K2O; but it may be N–P–K where permitted or required as specified by state law. Grades must be expressed in percentages of N-P-K for SSSA publications (oxide values may be included in parentheses). Compare fertilizer analysis.
fertilizer ratio The relative proportions of primary nutrients in a fertilizer grade divided by the highest common denominator for that grade, e.g., grades 10– 6–4 and 20–12–8 have a ratio 5–3–2.
fertilizer recommendation Refer to soil test interpretation.
fertilizer requirement The quantity of certain plant nutrients needed to increase nutrient availability in the soil with the objective of increasing plant growth to a designated level.
fibric material Organic soil material that contains 3/4 or more recognizable fibers (after rubbing between fingers) of undecomposed plant remains. Bulk density is usually very low and water holding capacity very high.
Fibrists
[soil taxonomy] A suborder of Histosols that are wet and have a high content of undecomposed plant fibers (e.g., the botanic origin of much of the organic material can be readily determined) and a low bulk density(less than about 0.1 g cm-3). The fiber content is more than two-fifths or more than three-fourths (depending on solubility in a sodiumpyrophosphate solution) after rubbing between the thumb and fingers. Commonly, Fibrists are saturated with ground water at or near the surface for periods long enough to limit their use for most crops unless they are artificially drained; the ground water fluctuates but seldom drops much below the bottom of the surface tier (USDA, 1999; Appendix I).
Fick's law The law describing the movement of ions or molecules by diffusion as caused by a concentration gradient.
field capacity, in situ (field water capacity) The content of water, on a mass or volume basis, remaining in a soil 2 or 3 days after having been wetted with water and after free drainage is negligible. Compare available water.
field strip cropping Refer to tillage, strip cropping.
fifteen-atmosphere percentage (no longer used in SSSA publications) The percentage of water contained in a soil that has been saturated, subjected to, and is in equilibrium with an applied pressure of 15 atm. Approximately the same as fifteen-bar percentage. Compare soil water.
fifteen-bar percentage (no longer used in SSSA publications) The percentage of water contained in a soil that has been saturated, subjected to, and is in equilibrium with, an applied pressure of 15 bars. Approximately the same as the fifteen-atmosphere percentage. Compare soil water.
fill [engineering geology] (a) Human-constructed deposits of natural earth materials (e.g., soil, gravel, rock) and waste materials (e.g., tailings or spoil from dredging) used to fill a depression, to extend shore land into a body of water, or in building dams. (b) Soil or loose rock used to raise the surface level of low-lying land, such as an embankment to fill a hollow or ravine in roads construction ( Jackson, 1997).
filled marshland A subaerial soil area composed of fill materials (construction debris, dredged or pumped sandy or shell-rich sediments, etc.) deposited and smoothed to provide building sites and associated uses (e.g., lawns, driveways, parking lots). These fill materials are typically 0.5 to 3 m thick and have been deposited unconformably over natural soils (Schoeneberger and Wysocki, personal communication, 2013). Compare dredge spoil bank.
film water A thin layer of water, in close proximity to soil-particle surfaces, that varies in thickness from 1 or 2 to perhaps 100 or more molecular layers.
fine sand (a) A soil separate. Compare soil separates.(b) A soil textural class. Compare soil texture.
fine sandy loam A soil textual class. Compare soil texture.
fine texture (a) A broad group of textures consisting of or containing large quantities of the fine fractions, particularly of silt and clay. (Includes all sandy clay, silty clay, and clay textural classes.) (b) [soil taxonomy] A family particle-size class having 35 to 60% clay. Compare soil texture.
finger [water movement] A vertically elongated path of preferential water flow in soil. Compare preferential flow.
finger ridge [geomorphology] One in a group of small, tertiary spur ridges that form crudely palmate extensions of erosional remnants along the flanks or nose of larger ridges. Compare ballena, rib (Schoeneberger and Wysocki, personal communication, 2013).
fire, ground [forestry] A fire that consumes all organic material of the forest floor and also burns into the underlying soil itself, as, e.g., a peat fire. Differentiated from a surface fire on the basis of vulnerability to wind; in a surface fire, the flames are visible and burning is accelerated by wind, whereas in a ground fire, wind is generally not a serious factor.
firm A soil consistence term. Compare consistence.
firming Refer to tillage, firming.
first bottom (obsolete; colloquial: Midwest USA) An obsolete, informal term loosely applied to the lowest and most frequently flooded part of the flood plain (flood-plain step) of a stream. However, the frequency of flooding is inconsistently specified (Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997).
fissure vent An opening in earth’s surface of a volcanic conduit in the form of a crack or fissure rather than a localized crater; a roughly linear crack or area along which lava, generally mafic and of low viscosity, wells up to the surface, usually without any explosive activity. The results can be an extensive lava plateau (e.g., Columbia River Plateau; Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997). Compare crater [volcanic].
fixation The process by which available plant nutrients are rendered less available or unavailable in the soil. Not to be confused with dinitrogen fixation.
fjord A long, narrow, winding, glacially eroded, U-shaped and steep-walled, generally deep inlet or arm of the sea between high rocky cliffs of slopes along a mountainous coast. Typically it has a shallow sill or threshold of solid rock or earth material submerged near its mouth and becomes deeper far inland. A fjord usually represents the seaward end of a deep, glacially excavated valley that is partially submerged by drowning after melting of the ice ( Jackson, 1997).
flaggy [soil classification] Containing ≥15 but <35% of flagstones. Compare rock fragments.
flagstone A relatively thin, flat rock fragment, from 150 to 380 mm on the long axis. Compare rock fragments.
flat [geomorphology] (a) (adjective) Said of an area characterized by a continuous surface or stretch of land that is smooth, even, or horizontal, or nearly so, and that lacks any significant curvature, slope, elevations, or depressions. (b) (noun) An informal, generic term for a level or nearly level surface or small area of land marked by little or no local relief (Jackson, 1997). Compare mud flat.
flat planting Refer to tillage, flat planting.
flatwoods (colloquial–southeastern USA) Broad, low gradient (generally <1% slope but up to 2% near drainageways), low relief interstream areas and characterized by non-hydric, poorly drained soils (seasonal saturation or water table) at depths of 15 to 45 cm (6–18”), and naturally forested by pines that dominate the Lower Coastal Plain of the southeastern USA. Regional differences occur in dominant vegetation and soil material (e.g., in south Florida, soils are dominantly sandy Spodosols and the understory is dominantly saw palmetto). Hydropedologically and elevationally this landform occurs slightly above minor depressions (which have a seasonal water table at or above the surface), drainageways, and drainhead complexes, but below better drained and slightly higher small rises or knolls. Generally they are most extensive toward the interiors of low, broad interstream divides and away from drainageways (Schoeneberger and Wysocki, personal communication, 2013).
flexible cropping A strategy of growing adapted crops with cropping and fallow decisions at each prospective date of planting based on available water in the soil plus expected growing season precipitation and without regard to a predetermined rigidly adhered to cropping sequence.
flocculation The coagulation of colloidal soil particles due to the ions in solution. In most soils, the clays and humic substances remain flocculated due to the presence of doubly and triply charged cations.
flood plain The nearly level plain that borders a stream and is subject to inundation under flood-stage conditions unless protected artificially. It is usually a constructional landform built of sediment deposited during overflow and lateral migration of the stream.
flood-plain playa A landform consisting of very low gradient, broad, barren, axial-stream channel segments in an intermontane basin. It floods broadly and shallowly and is veneered with barren fine-textured sediment that crusts. Commonly, a flood-plain playa is segmented by transverse, narrow bands of vegetation, and it may alternate with ordinary narrow or braided channel segments (Peterson, 1981). Compare playa.
flood-plain splay A fan-shaped deposit or other outspread deposit formed where an overloaded stream breaks through a levee (natural or artificial) and deposits its material (often coarse-grained) on the flood plain ( Jackson, 1997). Compare crevasse.
flood-plain landforms A variety of constructional and erosional features produced by stream channel migration and flooding, e.g., backswamp, braided stream, floodplain splay, meander, meander belt, meander scroll, oxbow lake, and natural levee (Hawley and Parsons, 1980).
flood-plain step An essentially flat, terrace-like alluvial surface within a valley that is frequently covered by flood water from the present stream (e.g., below the 100 year flood level); any approximately horizontal surface still actively modified by fluvial scour and/or deposition (i.e., cut and fill and/or scour and fill processes). May occur individually or as a series of steps (Schoeneberger and Wysocki, personal communication, 2013; Rhue, 1975). Compare stream terrace.
flood-tidal delta A largely subaqueous (sometimes intertidal), crudely fan-shaped deposit of sand-sized sediment formed on the landward side of a tidal inlet (modified from Boothroyd et al., 1985; Davis, 1994; Ritter et al., 1995). Flood tides transport sediment through the tidal inlet and into the lagoon over a flood ramp where currents slow and dissipate (Davis, 1994). Generally, flood-tidal deltas along microtidal coasts are multi-lobate and unaffected by ebbing currents (modified from Davis, 1994; Subaqueous Soils Subcommittee, 2005). Compare flood-tidal delta slope.
flood-tidal delta flat The relatively flat, dominant component of the flood-tidal delta. At extreme low tide this landform may be exposed for a relatively short period (modified from Boothroyd et al., 1985; Subaqueous Soils Subcommittee, 2005).
flood-tidal delta slope An extension of the flood-tidal delta that slopes toward deeper water in a lagoon or estuary, composed of flood channels, inactive lobes (areas of the flood-tidal delta that are not actively accumulating sand as a result of flood tides), and parts of the terminal lobe of the flood-tidal delta (modified from Boothroyd et al., 1985; Subaqueous Soils Subcommittee, 2005).
flooding Accumulation of large amounts of runoff on the landscape as a result of rainfall in excess of the soil’s ability to drain water from the landscape before extensive inundation and ponding occurs. Compare irrigation.
floodwall (not recommended) Use levee.
floodway (a) A large-capacity channel constructed to divert floodwaters or excess streamflow from populous, flood-prone areas, such as a bypass route bounded by levees. (b) The part of the flood plain kept clear of encumbrances and reserved for emergency diversion of floodwaters ( Jackson, 1997).
floor [geomorphology] (a) (not preferred; refer to basin floor, valley floor). A general term for the nearly level, lower part of a basin or valley; (b) The bed of any body of water; e.g., the nearly level surface beneath the water of a stream, lake, or ocean ( Jackson, 1997).
flow The movement of a fluid through the soil or over its surface.
flow rate The volume of fluid that flows through a given area per unit of time. Refer to flux.
flow region Conceptualization that a representative elemental volume of soil at any point consists of distinguishable pore classes, each with unique flow and transport properties.
flow till A till, that may be either subglacial or supraglacial in origin. Flow till displays secondary transport, sorting, and/or fabric modification by plastic mass flow. Flow till exhibits weak stratification and sorting and may contain distorted layers indicative of lateral displacement and soft sediment deformation. The secondary flow processes obliterate most original till fabric and clast orientation. Compare subglacial till, supraglacial till, lodgment till, melt-out till (Schoenenberger and Wysocki, personal communication, 2013).
flow velocity (of water in soil) The volume of water transported per unit of time and per unit of cross-sectional area normal to the direction of water flow.
flume (a) Open conduit for conveying water across obstructions. (b) An entire canal elevated above natural ground. An aqueduct. (c) A specially calibrated structure for measuring open channel flows.
fluorescent antibody An antiserum conjugated with a fluorescent dye (e.g., fluorescein or rhodamine). Fluorescent-labeled antiserum can be used to stain burred slides or other preparations and visualize the specific microorganism (antigen) of interest by fluorescence microscopy. Compare immunofluorescence.
flute [glacial] A lineation or streamlined groovefurrow or ridge parallel to the direction of ice movement, formed in newly deposited till or older drift. They range in height from a few centimeters to 25 m, and in length from a few meters to 20 km. Refer to glacial groove ( Jackson, 1997).
fluve (Use drainageway) A roughly linear or elongated depression (topographic low) of any size, along which water flows, at some time. Compare interfluve (Petersen, 1981; Schoeneberger and Wysocki, personal communication, 2013).
Fluvents [soil taxonomy] A suborder of Entisols that form in recent loamy or clayey alluvial deposits. Commonly, they are stratified, and have an organic carbon content that decreases irregularly with depth. Fluvents are frequently flooded, unless protected by dams or levees, but are not saturated with water for periods long enough to limit their use for most crops (USDA, 1999; Appendix I).
fluvial (adjective) Of, or pertaining to, rivers or streams; produced by stream or river action. Compare alluvial, colluvial (Hawley and Parson, 1980).
fluvioglacial Refer to glaciofluvial deposits.
fluviokarst A karst landscape dominated by both (i) karst features (deranged and subsurface drainage, blind valleys, swallow holes, large springs, closed depressions, and caves), generally limited to low-lying interfluve areas, and (ii) surface drainage by large rivers, with associated fluvial features (adjacent stream terraces) and sediments (alluvium), that commonly maintain their surface courses and are fed by underground tributaries; the dominant karst in the eastern USA. Compare sinkhole karst, pavement karst, glaciokarst, karst (Monroe, 1980; Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013).
fluviomarine bottom The nearly level or slightly undulating, relatively low-energy, depositional environment with relatively deep water (1.0 to >2.5 m) directly adjacent to an incoming stream and composed of interfingered and mixed fluvial and marine sediments (fluviomarine deposits; Subaqueous Soil Subcomittee, 2005).
fluviomarine deposits Stratified materials (clay, silt, sand, or gravel) formed by both marine and fluvial processes, resulting from non-tidal sea level fluctuations, subsidence, and/or stream migration (i.e., materials originally deposited in a nearshore environment and subsequently reworked by fluvial processes as sea level fell, or visa versa as sea level rose. Compare estuarine deposit, lacustrine deposit, lagoonal deposit, marine deposit, overbank deposit (Schoeneberger and Wysocki, personal communication, 2013).
fluviomarine terrace A constructional coastal strip, sloping gently seaward and/or down valley, veneered or completely composed of fluviomarine deposits (typically silt, sand, fine gravel). Compare terrace, stream terrace, marine terrace (Schoeneberger, and Wysocki, 2013).
flux The time rate of transport of a quantity (e.g., mass or volume of fluid, electromagnetic energy, number of particles, or energy) across a given area. Compare flux density.
flux concentration The mass of solute per unit volume of fluid passing a unit area of soil during a unit time period, equivalent to the ratio of the solute flux to the water flux.
flux density The time rate of transport of a quantity (e.g., mass or volume of fluid, electromagnetic energy, number of particles, or energy) per unit area perpendicular to the direction of flow.
fly ash All particulate matter that is carried in a gas stream, especially in stack gases at a coal-fired plant for the generation of electric power; also name given to sediments from the same source, stock piled in settling ponds or spoil piles (Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997).
foc
(foc) Fraction of organic carbon in a soil.
fold [structural geology] A curve or bend of a planar structure such as rock strata, bedding planes, foliation, or cleavage ( Jackson, 1997).
fold-thrust hills A landscape along an orogenic belt margin underlain dominantly by sedimentary rocks that have undergone intensive structural deformation via a series of sub-parallel thrust faults and associated folds. The thrust faults typically merge along a regional, subhorizontal displacement (decollement) at the basement contact. The land area displays considerable relief, characterized by cuestas, hogbacks, strike valleys, dip slopes, scarp slopes, and structurally-controlled hills; also know as an overthrust belt (e.g., the Wyoming overthrust belt; Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997).
foliar diagnosis An estimation of plant mineral nutrient status from the chemical composition of selected plant parts, and the color and growth characteristics of the plant foliage.
Folists [soil taxonomy] A suborder of Histosols that are more or less freely drained, have an accumulation of organic soil materials mainly as forest litter that is<1 m deep to bedrock or to fragmental materials with interstices filled with organic materials. Folists are not saturated with water for periods long enough to limit their use if cropped. (i.e., saturated less than 30 cummulative days, annually), and are not artificailly drained. Commonly, folists have a udic or perudic soil moisture regime, but may have ustic, aridic, or torric regimes (USDA, 1999; refer to Appendix I).
food chain Movement of soil nutrients from one life form to another as a result of the different feeding habits and dietary requirements of the organisms in the soil ecosystem.
food web Diagram of interconnections of nutrient flow in soil ecosystems through food chains.
foothills A steeply sloping upland composed of hills with relief of 30 up to 300 m and fringes a mountain range or high-plateau escarpment. Compare hill, mountain, plateau (Schoeneberger and Wysocki, personal communication, 2013; Hawley and Parson, 1980).
footslope The hillslope position that forms the inner, concave surface at the base of a slope, and situated between the backslope and a toeslope. Compare summit, shoulder, backslope, and toeslope.
force An influence that produces or tends to produce motion or change in motion.
foredune A coastal dune or dune ridge oriented parallel to the shoreline, occurring at the landward margin of the beach, along the shoreward face of a beach ridge, or at the landward limit of the highest tide, and more or less stabilized by vegetation ( Jackson, 1997).
forest floor All organic matter generated by forest vegetation, including litter and unincorporated humus, on the mineral soil surface.
forest productivity The capacity of a forest to produce specific products (i.e., biomass, lumber) over time as influenced by the interaction of vegetative manipulation and abiotic factors (i.e., soil, climate, physiography). Net primary productivity (NPP) provides the fundamental measure of forest productivity. When measured at the point of foliar carrying capacity for all potential flora, NPP is a measure of potential site productivity. Rate of product growth, an economic component, is occasionally used as a partial measure of forest productivity.
formation [stratigraphy] The basic lithostratigraphic unit in the local classification of rocks. A body of rock (commonly a sedimentary stratum or strata, but also igneous and metamorphic rocks) generally characterized by some degree of internal lithologic homogeneity or distinctive lithologic features (such as chemical composition, structures, textures, or general kind of fossils), by a prevailing (but not necessarily tabular) shape, and is mappable at the earth’s surface (at scales of the order of 1:25,000) or traceable in the subsurface. Formation may be combined into Groups or subdivided into members. Compare bed (Hawley and Parson, 1980).
fosse [glacial geology] A long, narrow depression or trough-like hollow between the edge of a retreating glacier and the wall of its valley, or between the front of a moraine and its outwash plain ( Jackson, 1997).
fractal
A tangible object or mathematical function made up of parts similar to the whole in some way, such that any small part of it, enlarged, has the same statistical character as the original. Fractals are often employed in soil science to model soil aggregation, pore networks and soil fragmentation.
fractal dimension Refer to fractal, fractal dimension.
fractal, fractal dimension A measure of the dimensionality of a fractal object or function. Its value is generally a fractional number that is either less or greater than the Euclidean dimension of the space in which the fractal is embedded.
fracture A planar void between aggregates.
fragile land Land that is sensitive to degradation when disturbed such as with highly erodible soils, soils where salts can and do accumulate, and soils at high elevations.
fragipan [soil taxonomy] A natural, diagnostic subsurface horizon with very low organic matter, high bulk density, and/or high mechanical strength relative to overlying and underlying horizons; has hard or very hard consistence (seemingly cemented) when dry, but showing a moderate to weak brittleness when moist. The layer typically has redoximorphic features, is slowly or very slowly permeable to water, is considered to be root restricting, and usually has few to many bleached, roughly vertical planes that are faces of coarse or very coarse polyhedrons or prisms (USDA,1999).
fragmentation Refer to fractal, fragmentation.
fragmentation – The act of breaking apart a tangible object or mathematical function into pieces or fragments.
monofractals – Fractals that can be characterized by a single fractal dimension.
framework silicate Silicate type in which all four oxygens of each silica tetrahedron are shared with other tetrahedra.
free face
The part of a hillside or mountainside consisting of an outcrop of bare rock (scarp or cliff) that sheds colluvium to slopes below and commonly stands more steeply than the angle of repose of the colluvial slope (e.g., talus slope) immediately below (Jackson, 1997).
free iron oxides A general term for those iron oxides that can be reduced and dissolved by a dithionite treatment. Generally includes goethite, hematite, ferrihydrite, lepidocrocite, and maghemite, but not magnetite. Compare iron oxides.
freshwater marl A soft, grayish to white, earthy or powdery (dry), usually impure calcium carbonate precipitated on the bottoms of present-day freshwater lakes and ponds largely through the chemical action of algal mats and organic detritus, or forming deposits that underlie marshes, swamps, and bogs that occupy the sites of former (glacial) lakes. The calcium carbonate may range from 90% to less than 30%. Freshwater marl is usually gray; it has been used for fertilizer for acid soils deficient in lime. Compare marl, coastal marl (Schoeneberger and Wysocki, personal communication, 2013).
friable A consistency term pertaining to the ease of crumbling of soils. Compare consistence.
friction cone penetrometer A cone penetrometer with the additional capacity of measuring the local side-friction component of penetration resistance. The resistance to penetration developed by the friction sleeve equals the vertical force applied to the sleeve divided by its surface area. Compare cone penetrometer, cone index, and penetration resistance.
frigid [soil taxonomy] A soil temperature regime that has mean annual soil temperatures of >0°C but <8°C,>5°C difference between mean summer and mean winter soil temperatures at 50 cm below the surface, and warm summer temperatures. Isofrigid is the same except the summer and winter temperatures differ by <5°C.
fringe-tidal marsh Narrow salt marsh adjacent to a relatively higher energy environment (Subaqueous Soil Subcommittee, 2005).
fritted trace elements Sintered silicates having total guaranteed analyses of micronutrients with controlled, relatively slow, release characteristics.
frost bursting (not recommended) Use frost shattering.
frost splitting (not recommended) Use frost shattering.
frost weathering (not recommended) Use frost shattering.
frost boil A small mound of fresh soil material formed by frost action. A type of nonsorted circle commonly found in fine-grained sediment underlain by permafrost, or formed in areas affected by seasonal frost. Compare patterned ground.
frost churning (not recommended) Use cryoturbation.
frost heaving Lifting or lateral movement of soil as caused by freezing processes in association with the formation of ice lenses or ice needles.
frost polygons (not recommended) use (periglacial) patterned ground.
frost riving (not recommended) use frost shattering.
frost shattering The mechanical disintegration, splitting, or breakup of a rock or soil caused by the pressure exerted by freezing water in cracks or pores, or along bedding planes. Sometimes referred to as congelifraction ( Jackson, 1997).
frost stirring (not recommended) Use cryoturbation.
frost wedging (not recommended) Use frost shattering.
frost, concrete Ice in the soil in such quantity as to constitute a virtually solid block.
frost, honeycomb Ice in the soil in insufficient quantity to be continuous, thus giving the soil an open, porous structure permitting the ready entrance of water.
fulvic acid The pigmented organic material that remains in solution after removal of humic acid by acidification. It is separated from the fulvic acid fraction by adsorption on a hydrophobic resin at low pH values. Compare soil organic matter.
fulvic acid fraction Fraction of soil organic matter that is soluble in both alkali and dilute acid.
functional nutrient Chemical elements that function in plant metabolism whether or not their action is specific.
fungistat A compound that inhibits or prevents fungal growth.
furrow Compare tillage, furrow; irrigation, furrow.
furrow mulching
Compare erosion, furrow mulching.