Glossary of Soil Science Terms - Browse

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).

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 fragmentationfractal 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