Glossary of Terms used in
Soil and Landscape Science
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iii
Contents
Glossary of Terms used in Soil and Landscape Science 1
A 1
B 6
C 9
D 15
E 18
F 23
G 27
H 30
I 32
J 34
K 34
L 35
M 39
N 42
O 43
P 45
Q 54
R 54
S 59
T 71
U 74
V 76
W 77
X 79
Y 80
Rankings for Physical Laboratory Test Results in Soil Landscape
Descriptions 81
Rankings for Chemical Laboratory Test Results in Soil Landscape
Descriptions 82
Glossary of Terms used in Soil and Landscape Science
1
Glossary of Terms used in Soil and Landscape
Science
This is a compilation of terms used to describe various aspects of a soil landscape’s
landform, topography, geology, native vegetation, land use, land degradation, soils, qualities,
limitations, hazards and recommendations for sustainable land use.
This document also includes rankings for laboratory test results used in Soil Landscape
Series products.
A
A horizon
Surface mineral horizon(s) with some organic accumulation; either
darker in colour than underlying horizons, or lighter in colour but with a
lower silicate clay/sesquioxide content.
abrupt boundary
Soil layer boundary 5 – 20 mm wide.
Acid Peats
(Great Soil Groups classification) These soils show little horizon
development, their main feature being the accumulation of a surface
horizon of almost black, strongly acid, peaty organic matter which is
maintained near saturation with water. The peat is generally well-
decomposed and sticky but significant amounts of fibrous roots and
partly decomposed plant remains occur near the surface. The lower
part is commonly clayey or gravelly grading into the underlying mineral
material.
acid rock
Igneous rocks with >10% free quartz e.g. rhyolite, granite.
acid soil
Any soil with pH of <6.5.
acid sulfate soils potential
Acid sulfate soils are clays, muds and sometimes sands associated
with pyrite-rich marine sediments. They may also occur in association
with some sulfidic ore bodies and sulfur-rich parent materials (e.g.
some coals). These soils become extremely acid following exposure or
drainage as sulfur compounds are oxidised and converted to sulfuric
acid. This makes them corrosive to iron, steel, aluminium alloys and
concrete. Underground services should be avoided or rustproofed.
Actual acid sulfate soils are too acid for most plant species and are
difficult to vegetate. Very acid drainage waters from these soils can
profoundly disturb aquatic ecosystems. 1:25 000 acid sulfate soil risk
maps and an accompanying report are available for all low lying
coastal areas in NSW from the NSW Office of Environment and
Heritage.
acid volcanics
Extrusive igneous rocks with a high percentage of silica-rich minerals
e.g. rhyolite, andesite.
acidification hazard
(Soil Landscape terminology) Poorly buffered soils, especially those
with expected buffering capacities of <30 kmol(+) ha/10 cm/pH unit
Glossary of Terms used in Soil and Landscape Science
2
show rapid increases in acidity. Soils can become more acid under
land management systems that have net acid input, such as nitrogen
leaching. Poorly buffered soils are usually sandy. In these soils, it is
very important to maintain high levels of organic matter.
acidity
(Soil Landscape terminology) Extremely and strongly acid soils with
laboratory measured pH (1:5 soil:water) values <5.5 often give rise to
acid soil infertility. Associated problems include toxic levels of
aluminium and/or manganese and deficiencies of most nutrients
(especially calcium and molybdenum). While many native plants in
eastern NSW have adapted to acid soil conditions, susceptible species
may require heavy applications of lime or dolomite and often fertiliser
to raise the pH (and nutrient supply) to a satisfactory level. Acid soils
may corrode untreated underground metal installations.
actual acid sulfate soil
Acidic soil material resulting from the oxidation of iron sulfides. The soil
material has a pH <4.0 (1:5 soil:water) when measured in dry season
conditions and can be identified by one of the following: Yellow mottles
and coatings of jarosite (straw yellow with a Hue of 2.5Y or more
yellow and with a Chroma of 6 or more); underlying potential acid
sulfate soils; or >0.05% water soluble sulfate. Can also be referred to
as sulfuric materials. See also potential acid sulfate soils.
adamellite
Quartz monzonite; a granitic rock in which quartz comprises 10 – 50%
of the felsic constituents and in which the alkali feldspar/total feldspar
ratio is between 35 – 50%; the approximate intrusive equivalent of
rhyodacite.
aeolian
A term applied to deposits of soil materials transported and/or
arranged by wind.
Aeolian Soil Landscape
(Soil Landscape terminology) Soil landscapes that have accumulated
by deposition of sand-sized particles by wind action. Aeolian soil
landscapes include dune fields, dunes, blow-outs, sand sheets,
lunettes and barrier ridges
agglomerate
Cemented mix of angular, fragmental volcanic material with fragments
>20 mm in size.
aggradation, aggraded
The process of the building up of surfaces, such as streambeds or
floodplains by the deposition of sediment and/or colluvium.
aggregate (soil)
A unit of soil structure consisting of primary soil particles held together
by cohesive forces or by secondary soil materials such as iron oxides,
silica or organic matter. Aggregates may be natural such as peds or
formed by tillage such as crumbs and clods.
aggregation
Soils in which the primary particles are bound together into units
known as aggregates. Forces contributing to aggregation include
electrostatic forces on clay particles, cementing substances from
organic matter or iron hydroxides, or plant roots and fungal hyphae.
AHD
Australian Height Datum, approximately mean sea level.
Glossary of Terms used in Soil and Landscape Science
3
air-filled porosity, AFP
(Soil Landscape terminology) Air-filled porosity is the amount of soil
occupied by air, which varies with moisture content. Most plants cease
to grow when air porosity is <10%; air-filled porosity of ≥10% is usually
considered to be suitable for most plants (Hazelton and Murphy 1992).
Air-filled porosity is rated as per Wesseling (1974).
• <1%— very low (VL)
• 1 – 5%— low (L)
• 5 – 20%— moderate (M)
• 20 – 30%— high (H)
• >30%— very high (VH).
alcove
Moderately inclined to very steep, short open depression with a
concave cross-section, eroded by collapse, landslides, creep or
surface wash.
alkaline soil
Alkaline soils have laboratory measured pH values >8.5. Alkalinity may
inhibit the growth of plants.
alkalinity
(Soil Landscape terminology) Alkaline soils have laboratory measured
pH (1:5 soil:water) values >8.5. Alkalinity may inhibit the growth of
plants. High levels of carbonate or bicarbonate may impair the uptake
of iron, manganese, copper and zinc. These soils are frequently sodic
or saline.
allelopathy
The effect of chemical products of one plant (usually reducing growth,
survival or reproduction) on another plant.
alluvial fan
Level to very gently inclined complex pattern of extremely low relief.
The rapidly migrating alluvial stream channels are shallow to
moderately deep, locally numerous, but elsewhere widely spaced. The
channels form a centrifugal to divergent, integrated, reticulated to
distributary pattern. Includes areas that are bar plains being aggraded
or eroded by frequently active channelled streamflow, and other areas
comprising terraces or stagnant alluvial plains with slopes that are
greater than usual formed by channelled stream flow but now relict;
incision in the upslope area may give rise to an erosional stream bed
between scarps. Typical elements are streambed, bar and plain.
Includes scarp. See also sheet-flood fan; pediment; stagnant alluvial
fan.
alluvial plain
Large flat area of alluvium. Although it includes floodplains, the
preferred use of the term is to describe former flood plains where there
is no recent accumulation of sediment. See also stagnant alluvial plain.
Alluvial Soils
(Great Soil Group classification) Soils developed from recently
deposited alluvium, normally characterise little or no modification of the
deposited material by soil forming processes, particularly with respect
to soil horizon development.
Alluvial Soil Landscape
(Soil Landscape terminology) Soil landscapes formed by deposition
along rivers and streams. Soil parent material is usually deep, sorted
and often stratified or previously stratified alluvium Alluvial soil
landscapes include current floodplains and alluvial deposits. Typical
landform elements include those found on meander plains including
Glossary of Terms used in Soil and Landscape Science
4
bars, back plains, scrolls, scroll plains, flood-outs, oxbows, levees,
lower terraces, prior and current stream channels.
alluvial terrace
Former floodplain which either no longer floods or rarely floods due to
deepening or enlargement of the stream channel.
alluvium/alluvial
A deposit of sand, mud or similar substances formed by flowing water.
Alpine Humus Soils
(Great Soil Group classification) Characterised by a marked
accumulation of well-humified organic matter that is intimately
incorporated into the mineral soil to form thick surface horizons of
profiles otherwise showing little horizon development.
Aluminium toxicity
potential
High levels of soluble aluminium are often toxic to non-native plants
such as some pasture, crop and ornamental species. Toxicity can be
expected when exchangeable aluminium levels are >5%, and soils are
strongly acid. Many species of native plants tolerate soils with high
concentrations of soluble aluminium. Lime or dolomite can be applied
to raise soil pH and thus reduce exchangeable aluminium.
ameliorant
A substance used to improve the chemical or physical qualities of the
soil. For example, the addition of lime to the soil to increase pH to the
desired level for optimum plant growth or the addition of gypsum to
improve soil structure.
amphibolite
Crystalloblastic rock consisting mainly of amphibole and plagioclase
with little or no quartz.
amygdaloidal
Descriptive term for lavas (i.e. basalt) with cavities formed by the
evolution of gas by the lava. The cavities are often subsequently filled
by a mineral such as quartz.
anaerobic
Describes soil conditions in which free oxygen is deficient and
chemically-reducing processes prevail. Such conditions are usually
found in waterlogged or poorly drained soils in which water has
replaced soil air.
anastomotic plain
A floodplain with slowly migrating deep stream channels, usually
moderately spaced, forming a divergent to unidirectional integrated
reticulated network. There is frequently active aggradation by overbank
and channelled stream flow. Typical elements are stream channel,
levee, back plain (dominant) See also alluvial plain; floodplain.
andalusite
An aluminium nesosilicate mineral (Al
2
SiO
5
) that forms under high
pressure and/or temperature; its presence is indicative of higher grade
metamorphism.
andesite
Dark coloured, fine-grained intermediate extrusive rock dominated by
plagioclase, pyroxene and/or hornblende with lesser quantities of
biotite, quartz, magnetite or sphene. The extrusive equivalent to
diorite.
angular blocky
Soil particles are arranged around a point and bounded by six
relatively flat, roughly equal faces with re-entrant angles between
adjoining faces few or absent. There is usually considerable
Glossary of Terms used in Soil and Landscape Science
5
accommodation of ped faces to the faces of surrounding peds. Most
vertices between adjoining faces are angular.
Anthroposols
(Australian Soil Classification) Soils resulting from human activities.
anticline
A fold in rock that is bowed upward with the oldest rocks at the centre
of the fold.
apedal
In the moderately moist to moist state, none of the soil material occurs
in the form of peds. It is massive or single-grained and, when
disturbed, separates into fragments or primary particles.
aplite
A fine to medium-grained light-coloured igneous rock typically
occurring as thin (<20 cm) veins within coarser-grained plutonic rocks.
aquiclude
A regolith or rock material which will not transmit water.
aquifer
A porous regolith or geological formation, often lying between
impermeable subsurface strata, which holds water, through which
water can percolate slowly over long distances and which yields
groundwater to springs and wells. Aquifers may, however, be
unconfined and the water level subject to seasonal inflow.
arboreal
Pertaining to trees.
arenite
The general term for any sedimentary rock with sand-sized grains.
argic horizon
A subsoil horizon consisting of distinct lamellae.
argillite
A low-grade metamorphic rock intermediate between mudstone and
shale.
arkose
A sandstone, usually derived from a granitic rock, which usually
contains ≥25% feldspars.
artesian basin
A structural basin of sedimentary rocks in the earth’s crust which
produces a constant supply of water. This rises to the ground surface
by means of a natural artesian spring or via a man-made bore from a
subterranean aquifer.
Associated Soil
Landscape
(Soil Landscape terminology) Soil landscapes whose area on the map
is of limited extent (usually <5 km
2
). Often, associated soil landscapes
occur on adjacent map sheets. Associated Soil Landscapes are briefly
described in the appropriate section (by soil landscape grouping).
Laboratory tests are not usually carried out on soil materials within
associated soil landscapes.
Associated Soil Material
(Soil Landscape terminology) Associated soil materials, that are
ephemeral or have limited extent, are briefly described. Soil tests are
not usually undertaken on these materials.
Australian Soil
Classification, ASC
Australia's national soil classification, a multi-category scheme with
classes defined by diagnostic horizons or materials and their
Glossary of Terms used in Soil and Landscape Science
6
arrangement in vertical sequence as seen in an exposed soil profile;
developed by the late Ray Isbell (CSIRO).
ash
Unconsolidated fine-grained material ejected during volcanic eruptions.
augite
((Ca,Na)(Mg,Fe,Al)(Si,Al)
2
O
6
) The most common type of pyroxene.
available soil water
That part of the water in the soil that can be absorbed by plant roots,
that can be held between field capacity and the moisture content at
which plant growth ceases.
available water holding
capacity
The ability to hold that part of the water in the soil that can be
absorbed by plant roots. Available water is the difference between field
capacity and permanent wilting point.
B
B horizon
Subsoil horizon(s) characterised by one or more of the following:
concentration of silicate clay, iron, aluminium, and/or organic material;
different structure and/or consistency to adjacent horizons; and/or
stronger colours than adjacent horizons.
backplain
Large flat resulting from aggradation by overbank stream flow at some
distance from the stream channel and, in some cases, having
biological (peat) accumulations; often characterised by a high
watertable and the presence of swamps or lakes; part of a covered
plain.
backswamp
Almost level, closed or almost closed depression bounded in part by
either hillslopes or dunes. Has a seasonal or permanent watertable at
or above the surface.
bank (streambank)
Very short but laterally extensive slope, moderately inclined to
precipitous, forming the margin of a stream channel and resulting from
erosion or aggradation by channelled streamflow; part of a stream
channel.
bar
Elongated, gently to moderately inclined low ridge built up by
channelled stream flow; part of a streambed.
bar plain
A floodplain with numerous rapidly migrating, shallow, alluvial channels
forming a unidirectional integrated reticulated network. Active
aggradation and erosion by channelled stream flow are frequent.
Typical elements are streambed, bar (dominant). See also alluvial
plain; floodplain.
barrier beach
A narrow body of deposited sediment, extending along the coast,
which is permanently exposed above sea level (Langford-Smith and
Thom 1969).
barrier system
A compound formation comprising several beach ridges usually
parallel to each other. A barrier system is developed by progradation of
Glossary of Terms used in Soil and Landscape Science
7
a coast and involves the seaward development of one beach ridge
after another (Langford-Smith and Thom 1969).
basalt
A fine-grained, dark-coloured basic volcanic rock primarily composed
of plagioclase and pyroxene (low silica and high ferromagnesian
content).
basanite
Feldspathoidal olivine basalt.
base saturation
The percentage of total cation exchange capacity (CEC) saturated with
basic ions.
batholith
Large body of intrusive igneous rock, often in the form of several
distinct plutons.
batter
The excavated or constructed face of a dam wall, cutting or
embankment.
bauxites
Aluminous duricrusts.
bauxitic horizon
A soil horizon containing >20% (visual abundance estimate) of bauxite
nodules or concretions which are mostly uncemented. It has a
thickness of >0.1 m.
beach
Short, low, laterally extensive slope, gently or moderately inclined, built
up or eroded by waves, forming the shore of a lake or sea.
Beach Soil Landscape,
Beach/Barrier Soil
Landscape
(Soil Landscape terminology) Soil landscapes which have ground
surfaces and soil parent materials that have been deposited by wave
action, including accumulation of sand-sized coastal sediments during
sea level changes. They typically occur near sandy coastlines or close
to lake edges. Typical landform elements include bars, beaches,
berms, beach ridges, dunes, swales, foredunes and some sandplains.
beach ridge
Elongated, nearly straight, low ridge built up by waves and usually
modified by wind; often a relict feature remote from the beach.
beach ridge plain
Level to gently undulating with extremely low relief on which stream
channels are absent or very rare. Consists of relict parallel beach
ridges. Typical elements are beach ridge (co-dominant), swale (co-
dominant). Includes beach, foredune, tidal creek. See also chenier
plain.
bedrock
Solid rock underlying the soil profile or other surface materials. It does
not necessarily represent the parent material of the overlying soil.
bench
Short, gently or very gently inclined minimal mid-slope or flat, eroded
or aggraded by any agent.
bentonite
A clay usually formed by the weathering of volcanic ash and which is
largely composed of montmorillonite type clay minerals. It has great
capacity to absorb water and swell accordingly. For this reason, it is
used to seal dams and/or earth embankments built of coarse materials
or which contain a coarse-textured seam causing them to leak.
Glossary of Terms used in Soil and Landscape Science
8
berm
A level area of loose sand between the upper limit of the swash zone
and toe of the foredune, formed from marine deposition.
biotite
(K(Mg,Fe)
3
(AlSi
3
O
10
)(OH)
2
) A brown/green mica, a layered silicate.
bioturbation
Movement of soil material within the soil profile by animals or plants.
Black Earth
(Great Soil Group classification) Black, heavy clay, alkaline to neutral
soil with wide, deep cracks when dry.
bleach/bleaching
The near-white colouration of an A
2
horizon which has been subjected
to chemical depletion because of soil-forming processes including
eluviation. The colour is defined for all Hues as having a value of ≥7
with a chroma of ≤4, on dry soils. Conspicuous bleaching means that
>80% of the horizon is bleached, whereas sporadic bleaching means
that <80% of the horizon is bleached, with affected portions appearing
irregularly through the horizon.
bleached loams
Soils with a uniform loam texture and a conspicuously bleached A
2
horizon.
bleached red earths
Red earths with a bleached A
2
horizon.
bleached yellow earths
Yellow earths with a bleached A
2
horizon.
block gliding
Displacement of blocks of sandstone gliding away from cliff faces.
blow-out
Usually small, open or closed depression excavated by wind.
bole
A fossil soil now interbedded between two basaltic lava flows. The
presence of a bole indicates that tropical climates prevailed during its
formation.
bolus
A small handful of soil which has been moistened and kneaded into a
soil ball which just fails to stick to the fingers.
borrow area
An area or excavation from which soil, clay, sand, rock or gravel has
been excavated for a specific purpose.
boundaries
The boundary between soil horizons defines the nature of the change
from one horizon to the next below. It is specified by two terms: one is
a measure of the width of the transition zone between the two
horizons; the other is a description of its shape.
breccia
Rocks comprising sharp angular fragments in a fine-grained matrix.
Brown Clay
See Grey, Brown and Red Clays.
Brown Earth
(Great Soil Group classification) Uniform yellowish, reddish or brown,
moderately acid to neutral light loams to clay with a crumb or fine
subangular blocky structure, showing little profile differentiation.
Brown Hardpan Soil
See Red and Brown Hardpan Soils.
Glossary of Terms used in Soil and Landscape Science
9
Brown Podzolic Soil
(Great Soil Group classification) Acid, mainly brownish to yellowish
soils, lacking or with a weak A
2
horizon and generally have weakly to
moderately differentiated profiles with merging horizons.
buffering capacity
The ability of the soil to resist changes in pH. The buffering action is
mainly to the properties of clay and fine organic matter. Thus, with the
same pH level, more lime is required to neutralise a clayey soil than a
sandy soil or a soil rich in organic matter than one low in organic
matter.
bulk density, estimated
(BD PAWCER)
(Soil Landscape terminology) Bulk density is the dry weight of soil per
unit volume. It affects air porosity and soil strength. The assessment of
bulk density is based on a model to estimate plant available capacity
called Plant Available Water Capacity Estimation Routine (PAWCER)
from version 2.1 developed from Littleboy (1997). The algorithm for
estimating bulk density requires 15 bar (pressure) moisture content,
clay, silt, coarse sand, fine sand and lower depth.
This method has been tested on soil data from Queensland and
northern NSW. All soil materials submitted for soil analysis have
PAWCER bulk density undertaken as routine laboratory testing
procedure for all soils within the following texture ranges: 5 – 75% clay,
5 – 50% silt, 15 – 80% fine and coarse sand totals. Soil materials
whose texture ranges fall outside these parameters are not calculated
by PAWCER, and the Interp software provides default ranking of 1.4.
The PAWCER program provides estimates based on the mineral
components of the soil. Higher than expected estimates are likely to
occur for soils higher in organic matter.
Rankings for bulk density are based on Table 8.2 in Handreck and
Black (1984), Growing media for ornamental plants and turf. The
categories are:
• Very open— Sandy soils with very low bulk densities have large
pore spaces between soil aggregates. This makes it difficult for
the plant roots to extract moisture and nutrients. These soils are
highly permeable and have little capacity to retain moisture.
• Satisfactory— Bulk density is normally satisfactory for plant
growth and the medium is suitable for root growth with good pore
space, good water infiltration and adequate water availability.
• Very compact— Bulk density is high and soils are likely to be too
compact for plant roots to penetrate easily. The small soil pores
that are often present limit the availability of air to the roots; and
water can be held tightly by the soil making it more difficult for
plant roots to extract water and nutrients.
• Extremely compact— Bulk density is extreme and soils are
generally not suitable for plant growth without amelioration, such
as improving soil structure with gypsum and organic matter, and
reducing the movement of vehicles when soils are wet.
C
C factor
(Soil Landscape terminology) The mulch or armouring effect of surface
rocks can be roughly estimated from estimates of rock volume. The
Glossary of Terms used in Soil and Landscape Science
10
mulch effect may be considered as a minimum USLE cover factor
when estimating sheet and rill erosion on soil devoid of vegetation.
Estimated rock volume percentage ranges for multiplication factors
have been averaged for field-recorded gravel factors from Table 603-5
of United States Department of Agriculture (1983).
Minimum USLE cover factors do not equate with projected ground
cover factors. These can be obtained from Wischmeier and Smith
(1978).
C horizon
Layer(s) of consolidated or unconsolidated, generally partially
weathered material showing lack of pedological development and/or
presence of remnant geological structure or organisation e.g.
sedimentary laminae, ‘ghost’ rock structures such as saprolite.
Cainozoic period
Geological period from 65 million years ago, to present.
calcareous
Calcareous materials, particularly soils, contain significant amounts of
calcium carbonate. Describes rocks composed largely of, or cemented
by, calcium carbonate. A calcareous soil is one containing carbonate in
sufficient quantity to effervesce visibly when treated with cold dilute (N)
hydrochloric acid.
Calcareous Red Earth
(Great Soil Group classification) Red, massive, sandy to loamy soils
which are porous and 'earthy' in fabric with some free carbonates in
the lower part of the profile.
Calcareous Sand
(Great Soil Group classification) Sands that show no profile
development beyond some accumulation of organic matter in the
surface horizon when they have been fixed by vegetation for sufficient
time.
Calcarosol
(Australian Soil Classification Soil Order) Soils that are either
calcareous throughout the solum or at least directly below the A
1
horizon.
calcrete
Calcareous duricrust; a conglomerate of sand and gravel cemented by
calcium carbonate into a hard mass.
calcrete pan
A moderately, strongly or very strongly cemented layer of calcrete
which is continuous, or if discontinuous or broken, consists of >90% of
hard calcrete fragments.
caldera
Large basin-shaped depression, generally circular, around a volcanic
vent; may be a product of erosion (erosion caldera) or of collapse
following withdrawal or ejection of supporting lava below (collapse
caldera).
carbic materials
Organic debris (e.g. charcoal) accumulated by colluvial and alluvial
processes when torrential rain occurs following bushfires.
Carboniferous period
Geological period from 280 – 345 million years before present.
catena
A repetitive sequence of soils generally of similar age and parent
material encountered between hill crests and the valley floor. The soils
Glossary of Terms used in Soil and Landscape Science
11
in the sequence occur under similar climatic conditions but have
different characteristics due to variation in relief, drainage and the
history of the land surface. Such variations normally manifest in
differential transport of eroded material and the leaching, translocation
and re-deposition of mobile chemical constituents. In soil mapping, the
use of this term has been largely replaced by the more general term
toposequence.
cation exchange capacity
(CEC)
The total amount of exchangeable cations that a soil can absorb,
expressed in centimoles of positive charge per kilogram of soil.
Cations are positive ions such as calcium, magnesium, potassium,
sodium, hydrogen, aluminium and manganese, these being the most
important ones found in soils. Cation exchange is the process whereby
these ions interchange between the soil solution and the clay or
organic matter complexes in the soil. The process is very important as
it has a major controlling effect on soil properties and behaviour,
stability of soil structure, the nutrients available for plant growth, soil
pH, and the soil’s reaction to fertilisers and other ameliorants added to
the soil.
channel
Linear, generally sinuous, open depression, in parts eroded, excavated
and aggraded by channelled stream flow; may include stream bed,
banks and bars.
channel bench
A flat at the margin of a stream channel aggraded and, in part, eroded
by overbank and channelled stream flow; an incipient floodplain; is
sometimes referred to as ‘low terrace’, but the term ‘terrace’ should be
restricted to landform patterns above the influence of active
streamflow.
chenier plain
Level to gently undulating landform pattern of extremely low relief on
which stream channels are very rare. Consists of relict, parallel linear
ridges built up by waves, separated by and built over flats (mudflats)
aggraded by tides or overbank streamflow. Typical elements are beach
ridge (co-dominant), flat (co-dominant). Includes tidal flat, swamp,
beach, foredune, tidal creek. See also beach ridge plain.
Chernozem
(Great Soil Group classification) Like Black Earths, but of lower clay
content and more friable, having porous structural units. The profile
shows weak horizon differentiation with gradual boundaries. Soil
reaction is neutral to alkaline. See also degraded chernozems.
chert
A hard, dense sedimentary rock of interlocking quartz crystals, often
white or coloured; also called flint.
Chocolate Soil
(Great Soil Group classification) Brownish, acid, friable, moderately
pedal to fine blocky structured, clay loam soils with weak to moderate
horizon differentiation.
Chromosol
(Australian Soil Classification Soil Order) Soils with a clear or abrupt
textural B horizon where the major half of the B
2
horizon is not strongly
acid.
cirque
Precipitous to gently inclined and typically closed depression of
concave cross-section and profile excavated by ice; the closed part of
Glossary of Terms used in Soil and Landscape Science
12
the depression may be shallow, the larger part being an open
depression like an alcove.
clay
Fine-grained material with particles <0.002 mm diameter; composed
normally of hydrated aluminium silicate minerals and plastic when
moist. Forms a smooth plastic bolus; slight to firm resistance to
shearing between thumb and forefinger; handles like plasticine; will
form ribbon of 50–75 mm or more; approximate clay content 35 – 50%
or more.
clay loam
Coherent plastic bolus; smooth to manipulate; will form ribbon of
40 – 50 mm; approximate is clay content 30 – 35%.
claypan
A pan consisting of a concentration of dense clays in the subsoil. The
term is also used (colloquially) for the impermeable clay surface
produced because of scalding.
claystone
A sedimentary rock composed primarily of clay-sized particles. It does
not exhibit strong close-spaced planes of cleavage as slate does.
clear boundary
Boundary 20 – 50 mm wide.
cliff-footslope
Slope situated below a cliff, with its contours generally parallel to the
line of the cliff eroded by sheetwash or water-aided mass movement
and aggraded locally by collapsed material from above.
closed-grassland
Vegetation structure dominated by tussock, hummock or sod grasses
having foliage cover <70%.
closed-sedgeland
Vegetation structure dominated by sedges with a canopy cover
between 70 – 100% of the ground area.
coal
The metamorphic product of stratified plant remains.
coffee rock
A type of brownish sand rock or soil pan formed where iron oxides and
organic matter, which have leached through the soil profile, are
precipitated at or above a fluctuating watertable.
coherent
Two-thirds or more of the soil material, whether composed of peds or
not, will remain united at the given moisture stage unless force is
applied.
columnar
This ped shape is like prismatic but the peds are larger and their tops
are domed. Like prismatic, but the peds are usually larger and have
domed tops.
colluvial
Describes soil and rock material transported largely by gravity.
colluvial fills
Deep layer/s of materials transported by gravity and water down a
slope which accumulate in drainage lines.
Colluvial Soil Landscape
(Soil Landscape terminology) Soil landscapes affected by mass
movement. Soil parent material consists mostly of colluvial mass
movement debris including scree and talus along with other landslide,
mudflow and creep deposits. Colluvial soil landscapes usually include
Glossary of Terms used in Soil and Landscape Science
13
alcoves, cliffs, cliff-footslopes, scarps, landslides, talus, some
moderately inclined to precipitous hillslopes, and areas with
commonplace evidence of mass movement. Slope wash processes
are considered less dominant.
colluvium
Heterogeneous rock and soil detritus transported by non-fluvial
downslope processes, e.g., mass movement, sheetflow.
comendite
A glassy type of rhyolite.
competent
Ability of flowing water to transport large particles.
complex soils
(Soil Landscape terminology) Areas with two or more soil types that
switch over relatively short horizontal distances and have different
capabilities or require different management techniques. Management
practices cannot be satisfactorily matched to any single soil type. It is
often difficult to predict soil type distribution.
complex terrain
(Soil Landscape terminology) Areas where the nature of the land
surface changes over relatively short distances, forming a mosaic of
lands with different capabilities that are too small to manage
individually. Examples include badlands, steeply dipping banded rock
outcrops, intensively branched gullies and melonhole gilgai.
concavo-convex
A landform with a convex (waxing) upper slope and a concave
(waning) lower slope.
concretions
Spheroidal mineral aggregates; crudely concentric internal fabric can
be seen with naked eye; includes pisoliths and oliths.
cone
A hillock with a circular symmetry built up by volcanism; the crest may
form a ring around a crater.
conglomerate
Detrital sedimentary rock substantially composed of rounded particles
which are >2 mm diameter.
consistence
Consistence is a statement of the strength and nature of cohesion of a
hand sample of soil material as it occurs in the field. Like field texture,
it is determined by manipulation. It varies considerably by the moisture
content of the sample, so it is important to also record a value for soil
water status when testing.
contact metamorphism
Thermal metamorphism formed in country rocks adjacent to the
contact with an igneous intrusion.
coral reef
Continuously active or relict landform pattern built up to sea level of the
present day or of a former time by corals and other organisms. Mainly
level, with moderately inclined to precipitous slopes below sea level.
Stream channels are generally absent, but there may occasionally be
fixed deep erosional tidal stream channels forming a disintegrated non-
tributary pattern. Typical elements are reef flat, lagoon, cliff
(submarine). Includes beach and beach ridge.
Glossary of Terms used in Soil and Landscape Science
14
cordierite
((Mg,Fe)
2
Al
4
Si
5
O
18
.nH
2
O) A hydrated cyclosilicate (ring silicate)
commonly found in metamorphic rocks.
country rock
The rock bodies into which an intrusive mass of igneous rock intrudes.
coupe
A felling area within a logging operation.
covered plain
Floodplain with slowly migrating deep alluvial channels, usually widely
spaced and forming a unidirectional integrated non-tributary network.
There is frequently active aggradation by overbank streamflow. Typical
elements are stream channel, levee, backplain (dominant). Includes
swamp. See also alluvial plain; floodplain.
cowal
A swamp, small lake, small swampy depression or an old stream bed
often associated with stagnant and alluvial plains.
crabhole gilgai
Irregularly distributed small depressions and mounds separated by a
generally continuous shelf. The vertical interval is usually <0.3 m and
the horizontal interval is usually 3 – 20 m. The surface is almost level.
crater
Steep to precipitous closed depression excavated by explosions due to
volcanism, human action, or impact of an extra-terrestrial object
creep
Generally imperceptible but continuous movement of soil down a
slope.
crest
Landform standing above all or almost all points in the adjacent terrain.
It is characteristically smoothly convex upwards.
Cretaceous period
Period of geological time from 65 – 135 million years before present.
crevasse splay
Sediment fan deposited on a floodplain from a rupture in the levee of a
river.
cropping land
Land normally cultivated for agricultural production such as grain and
fodder production, rice and cotton but not for improved pasture or for
vegetables, flowers or trees. Alternative term is dryland farming.
crumb
A soft, porous, generally rounded soil aggregate 1 – 5 mm in diameter.
cryptogams
Collective term which includes mosses, algae, lichen and liverworts.
cusp
A small, horn shaped beach feature formed in the swash zone.
cut face
Slope eroded by human activity.
cutans
Coatings on ped surfaces which may include clay skins or coatings of
sesquioxide, manganese, ferromanganese, organic matter or
carbonate.
cut-over surface
A flat eroded by human activity.
Glossary of Terms used in Soil and Landscape Science
15
D
D horizon
Layer(s) showing contrast in pedological organisation to overlying A
and/or B horizons, but not C horizon or buried soil.
dacite
An extrusive igneous rock of quartz plagioclase, hornblende and
pyroxene. A fine-grained rhyolite, the extrusive equivalent of diorite.
dam
A ridge built up by human activity that closes a depression.
debris avalanche
A form of mass movement in which a combination of slumps, slides
and rock falls occur as a large mass of material that falls down valley
sides extremely rapidly under the influence of gravity.
debris dam
A small dam-shaped accumulation of debris on a slope which
obstructs the natural flow of water.
deflation basin
A hollow formed in sand by the removal of loose material by the wind.
degraded Chernozems
Chernozems with topsoil of unstable, inferior structure.
delta
Floodplain projecting into a sea or lake, with slowly migrating, deep
alluvial channels, usually moderately spaced, typically forming a
divergent integrated distributary network. Aggraded by frequently
active overbank and channelled stream flow that is modified by tides.
Typical elements are stream channel, levee, backplain (co-dominant),
swamp (co-dominant), lagoon (co-dominant). Includes beach ridge,
swale and tidal creek. See also alluvial plain; floodplain; chenier plain.
Deltaic/Estuarine Soil
Landscape
(Soil Landscape terminology) Occur where rivers and streams enter
large bodies of water such as the sea or inland lakes. Channel flow is
dissipated and is also modified by wave and/or (in the case of
estuarine soil landscapes) tidal action. Soil materials may also be
influenced by saline conditions in both cases. Typical landform
elements within estuarine soil landscapes include estuaries, deltas,
tidal creeks and flats, and parts of coastal lagoons. Typical landform
elements within deltaic soil landscapes include stream channels,
levees, back plains and some swamps and lagoons.
dense clays
Like Plastic Clays and Structured Clays (i.e. no suitable Great Soil
Group classification) but with densely-packed peds.
densipan
Earthy pan of very fine sand (0.02 – 0.05 mm). Fragments, both wet
and dry, slake in water. Densipans are less stable on exposure than
overlying or underlying horizons.
depression
Landform element that stands below all, or almost all, points in the
adjacent terrain. A closed depression stands below all such points; an
open depression extends at the same elevation, or lower, beyond the
locality where it is observed.
Glossary of Terms used in Soil and Landscape Science
16
Dermosol
(Australian Soil Classification Soil Order) Soils other than those with B
2
horizons that have structure more developed than weak throughout the
major part of the horizon.
Desert Loam
(Great Soil Groups classification) Soils which have moderate texture
contrast with thin, loamy A horizons clearly separated from structural
clay B horizons. brown to red colour, and alkaline reaction, commonly
strongly so in the deeper subsoil. Surface soil pH ranges from alkaline
to neutral.
Devonian period
Geological period from 395 – 345 million years ago.
diatomite, diatomaceous
earth
A soft rock compound consisting of siliceous remains of diatoms.
diatreme
A small explosive volcanic intrusion comprising varying amounts and
types of pyroclastic debris and surrounding country rock.
diffuse boundary
Soil layer boundary >100 mm wide.
dilatent
A diagnostic feature of soil materials with high silt content, this term
refers to the ability of the soil to flow when wet due to its low wet-
bearing strength.
dieback
(Soil Landscape terminology) Widespread death of branch tips and
senescent trees that may indicate any of several soil, land use or
landscape-related problems including salinity and rising water tables,
ecosystem imbalances, high grazing pressures, drought or changes in
soil fertility. Dieback may be addressed by establishing tree species
suited to soil landscape conditions.
diorite
A medium-grained intermediate plutonic rock composed primarily of
sodic plagioclase and hornblende, biotite or pyroxene.
dispersible soils
(Soil Landscape terminology) Often highly erodible and may have low
wet-bearing strengths. Often very hardsetting when dry, and form
surface crusts, restricting water entry and hampering seedling
emergence. They are prone to erosion and structural degradation and
require very careful management. They may be treated with lime or
gypsum. Dispersible soils have a Dispersion Percentage (D%) >50%,
or an Emerson Aggregate class of 1, 2 or 3, and may also have a
sufficiently high sodium content to be considered sodic.
dispersion percentage,
DP
(Soil Landscape terminology) A measure of soil dispersibility
representing the proportion of clay and fine silt (approximately <0.005
mm) in a soil which is dispersible, expressed as a percentage. It is
determined in the laboratory by comparing the amount of fine material,
in a soil sample, dispersed by a ten-minute shaking in water, with the
amount dispersed by a 120-minute shaking in water containing
dispersant. Highly dispersible clays have a high dispersion percentage.
dispersion, dispersible
The characteristic of soils relating to their structural breakdown into
individual particles in water. Usually associated with high levels of
exchangeable sodium on the clay fraction and low levels of soluble
Glossary of Terms used in Soil and Landscape Science
17
salts in the soil. These factors cause clay particles to separate in
water. As clay is one of the chief agents holding soil materials
together, this leads to collapse of the soil structure and consequent
instability.
Disturbed Soil Landscape
(Soil Landscape terminology) Soil landscapes dominated by ground
surfaces arising from human activity. Soil parent materials have been
moved, accumulated, removed or replaced (with soil or other items).
Landform elements include fill-tops, embankments, cut faces, cut-over
surfaces, dams, mounds and pits
dolerite
Intrusive igneous rock with lath-shaped plagioclase crystals included in
pyroxene crystals; also called diabase.
dolomite
A sedimentary rock consisting of calcium magnesium carbonate
(CaMg(CO
3
)
2
).
dominant peds
The most obvious peds in a disturbed soil sample. The relative
difference between the strength of cohesion within peds and the
strength of adhesion between peds is greater for dominant peds than
for subdominant peds.
drainage
(Soil Landscape terminology) Drainage is affected by soil permeability,
hydraulic gradient and the permeability of materials below the soil
profile. Soils that drain water quickly are highly permeable. They
usually have coarse textures (sands) and many interconnected pores.
Soils with rapid drainage often have low waterholding capacities.
Seedlings and newly established plants require regular, light irrigation.
Drainage is assessed per McDonald et al. (1990). The categories are:
• very poorly drained
• poorly drained
• imperfectly drained
• moderately well-drained
• well-drained
• rapidly drained.
For the ‘Landscape qualities and limitations for each soil landscape’
table (if included), poor drainage indicates very poorly or poorly
drained soils. These soils are likely to pond water for long periods.
They usually have clayey textures and mottled or greyish colours.
Special drainage may be required. Rapidly draining soils often lack
water storage capacity and may transmit pollutants rapidly to
groundwater.
drainage depression
A level to gently inclined, long, narrow, shallow, open depression with
smoothly concave cross-section, rising to moderately inclined
sideslopes, eroded or aggraded by sheetwash.
drainage plain
A longitudinally-extensive, level or gently-inclined area of sediment,
adjacent to a drainage line, built up by alluvial deposition during the
current regime of the drainage line. Such areas are subject to periodic
overland flow of water, may be subject to seasonal waterlogging and
have vegetation types that often indicate a wetter microenvironment
than the surrounding country.
Glossary of Terms used in Soil and Landscape Science
18
Dry Peat Podzol
Dry peat soils underlaid by a bleached mineral layer.
Dry Peat
Soils in which the profile is dominated by dry organic matter (e.g.,
Allocasuarina needles).
dry sclerophyll
Canopy cover between 30 – 70% and with maximum height >10 m;
dominated by sclerophyllous trees with a single lower stratum of
xerophytic shrubs and herbs.
dune
Moderately inclined to very steep ridge or hillock built up by wind.
Dune formation may be initiated by the entrapment of transported
material by wind-reducing vegetation or structures. Series of parallel
dunes are known as dune ridges. In the coastal environment, dune
ridges develop during periods of sea level fall.
dunefield
Level to rolling with very low or extremely low relief without stream
channels, built up or locally excavated, eroded or aggraded by wind.
Typical elements are dune, swale and blow-out. Dunes are normally
linear in form. However, when a blowout proceeds unchecked a U-
shaped dune results. This is known as a parabolic dune.
Duplex soil
A soil in which there is a sharp change in soil texture between the A
and B horizons (e.g., loam to clay). The soil profile is dominated by the
mineral fraction with a texture contrast of 1½ texture groups or greater
between the A and B horizons. Horizon boundaries are clear to sharp.
The texture change from the bottom of the A horizon to the top of the B
horizon occurs over a vertical distance of <10 cm (Northcote 1979).
See also Gradational soil, Principal Profile Form, Uniform soil.
duricrust
The hardened crust of soil formed by accumulation through
groundwater evaporation of iron, alumina, manganese, silica and other
elements.
dyke
An intrusive, generally vertically-oriented sheet-like body of igneous
rock that cuts across the bedding planes or structures of the
surrounding country rocks.
dystrophic
Soil with effective cation exchange capacity (eCEC) divided by 100 g
clay <5 mol(+)kg clay.
E
earthflow
A category of mass movement involving earth materials flowing
downslope like a viscous fluid. Displacement varies from extremely
slow to extremely rapid.
earthy fabric
The soil material is cohesive and contains pores but few, if any, peds.
Earthy Sands
(Great Soil Groups classification) A mainly sandy soil with an earthy
fabric and little texture differentiation from topsoil to subsoil
Glossary of Terms used in Soil and Landscape Science
19
edaphic
Referring to soil factors affecting plant growth; an edaphic plant
community is one distinguished by soil conditions rather than by other
factors such as climate.
electrical conductivity
(EC)
A measure of the conduction of electricity through water or a water
extract of soil. It can be used to determine the soluble salts in the
extract and hence soil salinity. The unit of electrical conductivity is the
siemens and soil salinity is normally expressed as millisiemens per
centimetre at 25
0
C. Conductivity values of 1.5 (1:5 soil:water) or 4.0
(saturation extract) indicate the likely occurrence of plant growth
restrictions.
eluviation
The downward removal of soil material in suspension or in solution,
from a layer or layers of a soil. The loss of material in solution is
described by the term leaching. Some of the eluviated materials are
typically deposited in lower layers or horizons.
embankment
Slope or ridge built up by human activity.
Emerson Aggregate Test
(EAT)
(Soil Landscape terminology) A classification of soil aggregates based
on their coherence in water. Small, dry aggregates are placed in
dishes of distilled water and their behaviour is observed. The
conditions under which they slake, swell and disperse allow the
different aggregates to be separated into eight classes. The test is
particularly valuable in a soil conservation context as it grades soil
aggregates by their stability in water. Values are:
Class Result
1 slakes complete dispersion
2 slakes some dispersion
3 slakes some dispersion after remoulding
4 slakes no dispersion, carbonate or gypsum present
5 slakes dispersion in shaken suspension
6 slakes flocculates in shaken suspension
7 no slaking swells in water
8 no slaking does not swell
Charman and Murphy (2007) modifies classes 2 and 3 by dividing
them into the following subclasses:
Subclass Dispersion
(1) slight milkiness immediately adjacent to the aggregate
(2) obvious milkiness, less than 50% of the aggregate is affected
(3) obvious milkiness, more than 50% of the aggregate is
affected
(4) total dispersion, leaving only sand grains.
The sub-class is shown in brackets. For example, a Class 3 aggregate
that disperses completely on working, leaving only sand grains, is
recorded as Class 3(4).
Glossary of Terms used in Soil and Landscape Science
20
engineering capability
ratings
(Soil Landscape terminology) Engineering capability ratings rely mostly
on USCS classifications. They serve only as a guide to what can be
expected. Where dual (borderline) USCS classifications are given, the
most dominant classification is used for the interpretation. Seek
specialised engineering advice for specific recommendations.
engineering hazard
(Soil Landscape terminology) An assessment of the susceptibility of a
parcel of land to the prevailing soil and landscape qualities present that
will affect the stability of foundations for roads, buildings and related
infrastructure. Inappropriately designed structures built on land with
high engineering hazard can crack and become deformed, sometimes
also damaging underground services. In some areas, entire buildings
have been demolished, e.g. by mass movements. Geotechnical
engineering advice should be sought before development on land
identified as having moderate or high engineering hazard.
Eocene epoch
Geological epoch from 54 – 38 million years ago. It is the oldest
division of Tertiary rocks.
erodibility
The susceptibility of a soil to the detachment and transportation of soil
particles by erosive agents. It is a composite expression of those soil
properties that affect the behaviour of the soil and is a function of the
mechanical, chemical and physical characteristics of the soil. It is
independent of the other factors influencing soil erosion such as
topography, land use, rainfall intensity and plant cover, but may be
changed by management. The qualitative categories of soil erodibility
are low, moderate, high, very high and extreme. The most highly-
erodible soils are those that are most easily detached and transported
by erosive forces. High soil dispersibility is a good indicator of high soil
erodibility.
erodibility
(Soil Landscape terminology) The susceptibility of a soil to the
detachment and transportation of soil particles by erosive agents. It is
a composite expression of those soil properties that affect the
behaviour of the soil and is a function of the mechanical, chemical and
physical characteristics of the soil. It is independent of the other factors
influencing soil erosion such as topography, land use, rainfall intensity
and plant cover, but may be changed by management. The most
highly-erodible soils are those that are most easily detached and
transported by erosive forces. High soil dispersibility is a good indicator
of high soil erodibility.
For sheet and rill erodibility, the USLE K factor (Wischmeier and Smith
1978) of >0.04 is highly erodible. In some cases, sheet and rill
erodibility is modified by field assessment of factors such as existing
indications of previous sheet erosion, fabric and consistency that are
out of range or not accounted for by the USLE. Rankings for USLE K
factors are:
• very low (<0.01)
• low (0.01 – 0.02)
• moderate (0.02 – 0.04)
• high (0.04 – 0.06)
• very high (>0.06).
Glossary of Terms used in Soil and Landscape Science
21
These may be more broadly defined as:
• low (<0.01 – 0.02)
• moderate (0.02 – 0.04)
• high (>0.04).
erodibility, wind
(Soil Landscape terminology) Wind erodibility is the susceptibility of a
dry soil to detachment and transport by wind. It does not include other
factors such as climate or surface roughness. Wind erodibility is
assessed by measuring the percentage of air dry soil aggregates
retained by a
0.85 mm hand sieve (Craze et al. 1993). A wind erodible soil will have
a low percentage of retained aggregates. It is expected that sample
handling and transport of samples before reaching the laboratory will
decrease the proportion of retained aggregates.
If the volume of rocks (or gravel, if no coarse fragment data are
available) is <9.5%, then wind erodibility is very low (VL). For samples
where wind erodibility test results are available, the assessment based
on the US Soil Survey has been used (United States Department of
Agriculture 1983).
erosion
The wearing away of the land by running water, rainfall, wind, ice or
other geological agents including such processes as detachment,
entrainment, suspension, transportation and mass movement.
erosion hazard
(Soil Landscape terminology) The susceptibility of a parcel of land to
the prevailing agents of erosion. It is dependent on a combination of
climate, landform, soil, land use and land management factors. The
qualitative categories of erosion hazard are:
• Slight— indicates no appreciable erosion damage may occur
during development of a land use. Soil conservation management
should include simple practices such as establishment of
groundcover as rapidly as possible.
• Moderate— implies significant erosion may occur during
development of a land use. Provided appropriate soil conservation
measures are adopted during development, both short-term and
long-term erosion problems may be avoided.
• High— implies significant erosion may occur. Intensive soil
conservation measures are required to control erosion which will
occur during development of a land use. Short-term measures are
required in the initial stages of development, but long-term erosion
control would involve intensive measures being implemented.
• Very high— implies that significant erosion will occur both during
and after development of a land use. Planning will need to
carefully consider the balance between long-term erosion damage
and the maintenance and repair needed to ensure the viability of
the land use.
• Extreme— implies that erosion will occur to such an extent that
soil erosion control is impractical and uneconomic. These areas
are best retained as green timber and not used. Where urban
development proceeds despite this recommendation, detailed
engineering, geotechnical and other studies will be necessary.
Glossary of Terms used in Soil and Landscape Science
22
erosion hazard, water
(Soil Landscape terminology) Water erosion includes both sheet, rill
and gully erosion. Soil landscape descriptions typically provide an
assessment of erosion hazard for both non-concentrated flows (sheet
erosion) and concentrated flows (rill and gully erosion) under relevant
land uses. In these assessments, it is assumed that erosion hazard on
land under cultivation or permanent pasture is long-term whereas
erosion hazard in urban development is often confined to the
construction phase, i.e., from time of initial disturbance until a good
groundcover and appropriate stormwater drainage controls are
established. See also gully erosion, rill erosion, sheet erosion.
erosion hazard, wind
(Soil Landscape terminology) Areas subject to wind erosion typically
are exposed and have easily transported, unconsolidated, loose,
sandy and often dry topsoils. Soil landscape descriptions typically
provide an assessment of wind erosion hazard under relevant land
uses. Vegetative cover should be maintained to prevent erosion.
Erosional Soil Landscape
(Soil Landscape terminology) Soil landscapes that have been sculpted
primarily by the erosive action of running water. Streams are
well-defined and capable of transporting their sediment load. Soils are
usually shallow (with occasional deep patches) and mode of origin is
variable and complex. Soils may be either absent, derived from water-
washed parent materials or derived from in situ weathered bedrock. In
many instances, subsoils have formed in situ while topsoils have
formed from materials washed from further upslope. Erosional soil
landscapes usually consist of steep to undulating hillslopes and may
include tors, benches and areas of rock outcrop. Evidence of mass
movement is rare.
escarpment
Steep to precipitous landform pattern, forming a linearly extensive,
straight or sinuous, inclined surface which separates terrain at different
altitudes. A plateau will commonly be found atop the escarpment.
Relief may be high (hilly) or low (planar). The upper margin is often
marked by an included cliff or scarp. Typical elements are hillcrest and
hillslope. Includes cliff, scarp, talus, footslope and alcove.
estuarine
Pertaining to or formed in an estuary (brackish water). Relates to those
soil materials which have been under the influence of brackish water
during their deposition.
Estuarine Soil Landscape
See Deltaic/Estuarine Soil Landscape.
estuary
A stream channel close to its junction with a sea or lake where the
action of channelled stream flow is modified by tides and waves. The
width typically increases downstream.
Euchrozem
(Great Soil Groups classification) Red, strongly-structured clay soils
with a somewhat lower clay content near the surface. They resemble
Krasnozems but are more alkaline.
eutrophic
Base status >15 cmol(+)kg
-1
clay.
exchangeable sodium
percentage (ESP)
The proportion of the cation exchange capacity occupied by sodium
ions, expressed as a percentage. Sodic soils are categorised as those
Glossary of Terms used in Soil and Landscape Science
23
with an ESP of 6 – 14%, strongly sodic soils are those with an ESP
≥15%. Soils with a high ESP are typically unstable and consequently
have high erodibility and often present problems in soil conservation
earthworks.
extratidal flat
Tidal flat characterised by infrequent tidal inundation and seasonally
common freshwater inundation.
F
fabric
The appearance of the soil material using an 10 hand lens.
Differences in the presence or absence of peds, the lustre (or lack
thereof), ped surfaces, and the size and arrangement of pores in the
soil mass are noted. See also earthy fabric; sandy fabric; rough-ped
fabric; smooth-ped fabric.
facet
A part of a soil landscape, distinguished by topography, lithology
and/or soil type. Within individual soil landscape descriptions, facets
may be labelled on cross-section diagrams, or their positions may be
interpreted from type profile and topographic labelling. Facets are not
depicted on soil landscape maps of this series.
facies
A body of rock with specified characteristics, ideally a distinctive rock
that forms under certain conditions, reflecting a certain process or
environment. See also green schist facies.
fan
Large, gently inclined to level element with a radial slope inclined away
from a point, resulting from aggradation or occasionally from erosion
by channelled, often braided streamflow, or possibly by sheet flow.
fault
A planar rock fracture showing evidence of relative movement.
faunal casts
Soil matter reworked by passing through the digestive tracts of soil
animals.
feldspar/felspar
Aluminosilicates of potassium, sodium and calcium. Feldspar is
characterised by two cleavages at nearly right angles and is among
the most important constituents of igneous rock.
ferric horizon
One which contains >20% ferruginous nodules or concretions which
are mostly uncemented. Its thickness is >0.1 m.
ferricrete
Indurated material rich in hydrated oxides of iron (usually goethite and
hematite) occurring as cemented nodules and/or concentrations, or as
massive sheets; may be referred to as laterite, duricrust or ironstone.
ferromanganese
Pertaining to red and black concretions or nodules consisting of iron
(red) and manganese (black). These are often precipitated from
groundwaters that have fluctuating watertables.
ferromanganiferous
Ironstone gravels containing oxides of manganese; may be localised
within or scattered throughout the soil profile.
Glossary of Terms used in Soil and Landscape Science
24
Ferrosol
(Australian Soil Classification Soil Order) Soils with B
2
horizons in
which the major part has a free iron oxide content >5% iron (Fe) in the
fine earth fraction (<2 mm). Soils with a B
2
horizon in which >0.3 m has
vertic properties are excluded.
ferruginous cementation
The bonding of soil particles into a hard mass by the concentration of
iron around a nucleus.
fertility
(Soil Landscape terminology) As a soil quality, ‘fertility’ is an
assessment of the typical ability of a soil material to support plant
growth. However, the fertility of a soil material can be influenced by
many factors, and may vary for individual sites. Soil materials with poor
fertility usually require the application of chemical fertilisers or suitable
organic matter to support highly productive plant growth, although
some soil materials do not respond well to normal applications of
fertiliser. For example, soil materials with high aluminium or iron oxide
contents readily immobilise phosphate, making it unavailable to plants.
A soil material’s physical condition can also reduce plant growth. The
rankings used to describe the fertility of soil materials are:
• Low— not generally, or only marginally, suitable for highly
productive plant growth. It will have toxicity or extremely poor
chemical fertility, and/or significant structural or water storage
problems that will be expensive to overcome.
• Moderate— moderately suitable for highly productive plant
growth. It will have few chemical, structural and/or water storage
problems.
• High— well-suited for highly productive plant growth. It will have
modest to good physical and chemical fertility with few or no
structural or water storage problems.
As a landscape quality, ‘fertility’ is an assessment of the typical ability
of whole soil profiles to support plant growth. Properties of soil profiles
that contribute to fertility include the level of nutrients, toxic elements,
structural condition, the depth to which plant roots can penetrate,
stoniness, drainage and the typical sequences and thicknesses of soil
materials within the profile that may promote or restrict plant growth.
This assessment of fertility is a guide only and does not constitute
advice for any specific crop, pasture or horticultural use. Fertility is
ranked as low, moderate, high or variable.
The general concept of soil fertility may also be divided into three
components:
• Chemical fertility— refers to the supply of plant nutrients in the soil
• Physical fertility— refers to soil structural conditions providing for
aeration, water supply and root penetration
• Biological fertility— refers to the population of micro-organisms in
the soil and its activity in recycling organic matter.
fibric
Organic and fibrous; dark organic stain discolours fingers; greasy feel
in clayey textures and coherence in sandy textures. Fibres (excluding
living roots) or plant tissue remains are visible to the naked eye or
easily visible with ×10 hand lens.
Glossary of Terms used in Soil and Landscape Science
25
fibric (or fibrous) peat
Undecomposed or weakly decomposed organic material. Plant fibres
(other than living roots) are distinct, readily identifiable and make up
more than two-thirds of the material.
field capacity, FC
(Soil Landscape terminology) Field capacity is arbitrarily the amount of
water remaining after a saturated soil material has drained against
gravity. Field capacity is meaningful only for in situ soils that are
relatively freely-draining.
Field capacity is generally accepted to be equivalent to the water
content of an undisturbed core soil sample that has been drained by
10 kPa suction in a pressure vessel. Field capacity for soil survey is
measured on disturbed soil samples where some feld capacity-
contributing pores may have been destroyed; hence it is considered to
generally underestimate feld capacity for undisturbed soils. Field
capacity results may, however, be considered approximate for
disturbed soils. Gravimetric water content is converted to volumetric
water content by multiplication by soil bulk density. If bulk density is not
available, Interp assumes that bulk density is 1.4.
Soils with high field capacity can hold more soil water against drainage
by gravity than soil with low field capacity. All other things being equal,
soil materials in well-drained profiles with low field capacities are more
likely to dry faster than soil materials with higher feld capacities. High
field capacities tend to be more important where rainfall is low, erratic
or seasonal.
fill
Man-made deposits of rock, soil, tailings, etc.
fill-top
A flat aggraded by human activity.
fissile
A descriptive term for fine-grained sedimentary rocks that can split
easily along bedding plains.
floc condition
Refers to the general flocculent or aggregated appearance of the soil
mass especially when viewed under a ×10 hand lens.
flood hazard
(Soil Landscape terminology) Areas subject to periodic flooding by
stormwater run-off and overland flow by rivers and streams should be
retained as drainage reserves. Flood hazard is assessed from
geomorphic context and the presence of unconsolidated flood deposits
floodout
A flat inclined radially away from a point on the margin or at the end of
a stream channel, aggraded by overbank stream flow or by channelled
stream flow associated with channels developed within the overbank
flow; part of a covered plain.
floodplain
An alluvial plain characterised by frequently active erosion and
aggradation by channelled or overbank stream flow. Includes other
patterns: bar plain, meander plain, covered plain, anastomotic plain
and delta. See also alluvial plain.
flowline
A well-defined route down which water naturally concentrates and
flows. It is a general term including drainage depression, gully,
drainage line, creek and river.
Glossary of Terms used in Soil and Landscape Science
26
fluffy
Term used to describe soil (e.g. some Krasnozem topsoils) that is very
light and finely-structured.
fluted
Pattern of steep, closely-spaced ridges that occurs on basalts,
generally in those areas with <1,400 mm annual rainfall.
Fluvial Soil Landscape
See Alluvial Soil Landscape.
fold belt
An area of bending of the earth’s crust due to compressional force.
folding
Buckling or warping of rock due to compressional force.
footslope
A moderate to gently sloping landform at the lower end of a slope,
resulting from aggradation or erosion by sheetflow, earthflow or creep.
foredune
Elongated, nearly straight, moderately inclined to very steep ridge, built
up by the wind from material from an adjacent beach.
forest land grazing
The grazing of stock in uncleared forest areas ranging from woodland
(savannah woodland) to tall open forest (wet sclerophyll forest).
foundation hazard
(Soil Landscape terminology) The susceptibility of a parcel of land to
prevailing soil and landscape limitations that will affect the foundation
stability of roads, buildings and related infrastructure. It is primarily
determined by soil movement, which in turn is related to the soil’s
physical properties, soil moisture regime and weight loadings. Soil
chemical properties such as extreme acidity and salinity can also affect
foundations through corrosion of concrete and services.
Inappropriately designed buildings, structures and services built on or
in land with high foundation hazard may experience cracks and
deformations, whilst in some areas whole houses have been
demolished through mass movement. These conditions are expensive
to overcome but can often be avoided through appropriate planning
and design. When moderate to high foundation hazards occur, you
should seek advice from a professional geotechnical engineer. Further
investigation to identify and locate the whereabouts of these significant
hazards to foundation stability is required.
In soil landscape reports, foundation hazard refers to foundations
placed on or within in situ soil materials. It does not refer to structures
placed on fill or into bedrock or for large structures which require
detailed site investigation.
foundation stability rating
(Soil Landscape terminology) This assessment is based solely on soil
properties after Finlayson (1982). Final assessment should be
modified by many site conditions including drainage, geology, slope,
climate and soil depth. Building foundation stability is assessed for
small structures such as sheds and houses built on 300 mm wide
footings. Larger structures would require generally deeper sampling
depths.
If volume expansion is >21% or linear shrinkage is >13%, then the
very low (VL2) ranking applies. These soils normally require special
foundations depending on seasonal variations in soil moisture.
Glossary of Terms used in Soil and Landscape Science
27
frets
The wearing away or weathering of batter surface particles.
friable
Easily crumbled or cultivated.
fungal mat
Layer of soil material held together by fungal hyphae.
G
gabbro
A group of dark coloured, basic intrusive igneous rocks; the
approximate intrusive equivalent of basalt.
genus
A classification group composed of closely-related species.
geological time
Units of time in descending order of magnitude, i.e. era, period and
epoch.
geomorphic time
Scale of time, usually tens to hundreds of thousands of years, over
which geomorphic features are formed.
geomorphology
Relates to the form of the earth, the general configuration of its
surface, and the changes that take place in the evolution of landforms.
geotechnical report
Report on the engineering properties of the soil and terrain.
gilgai
Surface micro-relief associated with some clayey soils consisting of
hummocks and/or hollows of varying size, shape and frequency. This
phenomenon is a continuing long-term process due to the shrinking
and swelling of deep subsoils with changes in moisture content. It is
usually associated with the occurrence of expansive soils. See also
crabhole gilgai; lattice gilgai; linear gilgai; melonhole gilgai; normal
gilgai.
Gilgai Soil Landscape
(Soil Landscape terminology) Soil landscapes where seasonal
shrink-swell is the dominant soil process. They are characterised by
undulating microrelief, with small depressions, holes, shelves and
mounds. Drainage is typically disintegrated. Gilgai types include
crabhole, normal, linear, lattice, melonhole and contour.
gley, gleying
The grey or greenish-grey colouration found in soils. Gley is often
produced under conditions of poor drainage giving rise to chemical
reduction of iron and other elements. Any colour on the Munsell ‘gley’
charts.
Gleyed Podzolic Soil
(Great Soil Groups classification) Poorly-drained, acid soils with
strongly-differentiated profiles, including a bleached A
2
overlying
greyish or yellowish B horizons.
Gneiss
Coarse-grained banded crystalline rock formed during high-grade
regional metamorphism; most have a granitic composition with
minerals separating into schistose bands of micas and amphiboles and
granulose bands of quartz and feldspar.
Glossary of Terms used in Soil and Landscape Science
28
Gossan
A ferruginous deposit consisting principally of hydrated oxide of iron
which is the result of oxidation and removal of sulfur and copper. The
presence of pyrite is common.
Gradational soil
A soil in which there is a gradual change in soil texture between the A
and B horizons, e.g., loam over clay loam over clay (Northcote 1966).
See also Duplex soil, Principal Profile Form, Uniform soil.
gradual boundary
Boundary 50 – 100 mm wide.
Granite
Coarse-acidic plutonic igneous rock.
granitic
Pertaining to granite or granite-like rocks such as granodiorite and
adamellite.
granitoid
A general term describing intrusive or plutonic igneous rocks in which
the crystals are irregular, interlocking and of uniform size.
granodiorite
Coarse-intermediate intrusive igneous rock; the intrusive equivalent of
rhyodacite; contains quartz, oligoclase or andesine, potassium feldspar
and mafic minerals.
granophyre
Microgranite which displays granophyric texture i.e. intricate quartz-
feldspar intergrowths that may resemble ancient cuneiform lettering
and are referred to as ‘micrographic’.
granular
Spheroidal or polyhedral peds having planar or curved surfaces which
have slight or no accommodation to faces of surrounding peds. Peds
are relatively non-porous.
grassland
Grasses, single stratum of grasses and forbs.
gravel
The amount (i.e., visual abundance estimate) of gravel-sized (>2 mm)
materials that occur on the surface and in the A
1
horizon and, when
moist, include hard coarse fragments and segregations of pedogenic
origin.
gravelly
>60% of surface cover consists of gravel (2 – 60 mm).
Great Soil Groups
Classification of Australia,
GSG
Defined by Stace et al. (1968), the 43 (originally 47) Great Soil Groups
describe soil types in terms of morphology, genesis and land use.
green schist facies
Metamorphic facies, also applied to altered mafic volcanic rocks, with a
typical green colour due to abundant chlorite, actinolite and epidote,
and exhibiting schistocity, foliation and/or layering. It includes the
common products of low-grade regional metamorphism and is believed
to correspond to temperatures between 300 – 500° C.
Grey, Brown and Red
Clay
(Great Soil Groups classification) These form a broad group of soils
whose common properties are determined by their high clay contents.
Typically, they are moderately deep to very deep soils with uniform
colour and texture profiles, weak horizonation mostly related to
Glossary of Terms used in Soil and Landscape Science
29
structure differentiation and some carbonates and/or gypsum in their
subsoils. They crack deeply on drying.
greybilly
Rock found in sub-basaltic exposed sites and consisting of deposited
secondary silica.
Grey-brown and Red
Calcareous Soil
(Great Soil Groups classification) Shallow, soft, powdery or weakly
structured loams to light clays containing finely divided carbonates
throughout the solum and showing little pedological differentiation.
They are essentially sedentary soils formed from highly calcareous
rocks which underlie them at various depths. Fragments of limestone
are commonly present.
Grey-brown Podzolic Soil
(Great Soil Groups classification) Duplex soil with a clayey brownish
blocky B horizon. A bleached A
2
horizon might be present.
greywacke
Dark grey, firmly indurated sandstone with poorly-sorted quartz and
feldspar with dark rock and mineral fragments in a clayey matrix.
Sandstone with >15% clay minerals.
groundwater pollution
hazard
(Soil Landscape terminology) Areas with high water tables and soils
that are highly permeable with a low ability to retain nutrients are prone
to groundwater pollution. Pollutants such as nutrients, pesticides,
herbicides, detergents, sewerage seepage and other chemicals may
leach through these soils, causing contamination of the groundwater.
GSG
See Great Soil Groups Classification of Australia.
gully
An open depression with short, precipitous walls and moderately
inclined to very gently inclined floor or small stream channel, eroded by
channelled stream flow and consequent gravitational fall and water-
aided movement.
gully erosion
A complex of processes in which the removal of soil is characterised
by large incised channels in the landscape >0.3 m deep. The severity
of gully erosion may be recorded as minor, moderate, severe or very
severe.
Minor and moderate gully erosion is related to the density of gullies
within the primary drainage lines over a specified area. With minor
gully erosion, gullies are generally discontinuous, and with moderate
gully erosion, they are generally continuous. When branching of the
gullies away from the primary drainage line occurs, the severe
categories are used.
Three categories of gully depth may also be recorded: <1.5 m, 1.5 – 3
m and >3 m.
gully erosion risk
(Soil Landscape terminology) Areas with erodible and/or sodic or
dispersible soils, high run-on, highly intensive rainfall, and locations
where ground cover or surface soils have been disturbed or removed
are vulnerable to tunnelling and gully erosion. Methods to combat gully
erosion include engineered gully control structures (such as headwalls,
sediment traps and weirs) replanting affected areas with ground cover
species, and fencing off gullied areas to exclude stock.
Glossary of Terms used in Soil and Landscape Science
30
gypsic horizon
A horizon containing >20% visible gypsum that is apparently of
pedogenic origin and has a thickness ≥0.2 m.
gypsum
A naturally-occurring soft crystalline material which is the hydrated
form of calcium sulfate (CASO
4
2H
2
O). Deposits occur mainly in arid
inland areas of Australia. Contains ~23% calcium and ~18% sulfur.
H
hand auger
Hand-turned drilling device in which cuttings are continually removed
from the bottom of the bore. Also known as a post-hole digger.
hanging valley
An enclosed valley upstream of a nickpoint in the drainage line. Also,
where a tributary valley’s floor is at a higher level than the main valley
due to deepening of the latter by glacial erosion.
hard
The general term to indicate strength or soil or rock material.
hard rock
General term for geological units consisting of unweathered rock as
opposed to sediments such as river alluvium, sands or gravels.
hardsetting
Condition of a dry surface soil when a compact, hard and apparently
apedal structure forms. In cultivated soils, clods usually retain this
condition until completely broken down by repeated cultivation. Soils
which do not set hard are either pedal both when moist or dry, or are
apedal single-grained.
hardsetting soils
(Soil Landscape terminology) Soils that become hard, massive and
compact when dry. They do not easily absorb rainwater and they
cause high run-off with consequent soil erosion. They do not offer
favourable environments for seed germination and require careful
water management. Regular cultivation should be avoided, although
some cultivation may be necessary to break up the hard layer for
successful germination.
hardwood plantation
Land where the vegetation has been cleared and replaced with a
plantation of native hardwood species e.g. Eucalyptus spp.
heath
Vegetation community consisting of a typically dense (canopy cover
<30%) low (maximum height <2 m) upper stratum of shrubs with a
sporadic lower stratum of forbs.
hemic peat
Moderately to well-decomposed organic material. Plant remains vary
from most being difficult to identify to being unidentifiable. It is
intermediate in degree of decomposition between the less
decomposed fibric peat and the more decomposed sapric peat.
high-level subvolcanic
intrusion
Intrusions of fine-grained diorite, granodiorite or granite composition.
These intrusions might be circular or elliptical in outcrop with a
diameter 1 – 4 km (Thorpe & Brown 1985).
Glossary of Terms used in Soil and Landscape Science
31
hillcrest
Very gently inclined to steep smoothly convex crest, standing above a
hillslope, eroded mainly by creep and sheetwash (overland flow).
hills
Landform pattern of high relief (90 – 300 m) with gently inclined to
precipitous slopes. Fixed, shallow erosional stream channels, closely
to very widely spaced, form a non-directional or convergent, integrated
tributary network. There is continuously active erosion by wash and
creep and occasionally active erosion by landslides. Typical elements
are hillcrest, hillslope (dominant), drainage depression, streambed.
Includes footslope, alcove, valley flat, gully, tor, summit surface, scarp,
landslide talus, bench, doline. See also low hills; mountains; plain;
rises.
hillslope
Gently inclined to precipitous slope, commonly simple and maximal
and eroded by sheetwash, creep or water-aided mass movement;
typical element of mountains, hills, low hills and rises.
hobby farm
Type of land development, irrespective of allotment size but usually
relatively small, involving some form of agricultural enterprise which is
secondary to the owner’s main line of business.
Holocene epoch
Present geological epoch which commenced 10,000 years ago.
horizon
A layer within the soil profile with morphological characteristics and
properties different from layers below and/or above the layer.
hornblende
((Ca,Na)
2-3
(Mg,Fe,Al)
5
Si
6
(Si,Al)
2
O
22
(OH)
2
) Ferromagnesian mineral of
the amphibole group.
horst
An uplifted, fault-defined block of the earth’s crust.
horticultural land
Land used for production of fruits, vegetables, flowers or ornamental
plants.
horticulture
The science and art of growing fruits, vegetables, flowers or
ornamental plants.
humic
Referring to the organic matter within a soil.
humic cementation
The bonding of soil particles into a hard, brittle consistency by organic
substances within a soil.
Humic Gley
(Great Soil Groups classification) Soils that are acid to neutral, mainly
mineral soils with significant but widely varying organic matter contents
intimately incorporated in the dark A horizons. They grade into subsoils
marked by rusty and ochreous streaks and mottles on a pale grey
matrix. Below this mottled horizon, the soil is typically grey to bluish-
grey and permanently waterlogged, but the watertable fluctuates,
periodically rising almost to the surface.
hummock
A small, raised feature above the general ground surface.
humose horizon
This is a humus-rich surface or near-surface horizon that is ≥0.2 m
thick and has insufficient organic carbon to qualify as organic material.
Glossary of Terms used in Soil and Landscape Science
32
Humus Podzol
(Great Soil Groups classification) These soils have a dark A
1
horizon
of organic accumulation, a light grey or whitish A
2
horizon and a dark
grey to black, dominantly humic B horizon overlying water-saturated
and weakly mottled mineral soil.
Hydrophobic soils
Soils which resist wetting when dry. Drops of water do not spread
spontaneously over their surface and into pores. The degree of water
repellence may be severe where water drops remain on a flattened
surface for some minutes. In other cases, drops appear to be
absorbed readily but quantitative measurements show that the height
of capillary rise is diminished.
This characteristic is mainly a feature of some sandy soils (topsoils)
and is generally attributed to organic coatings on the sand grains
which resist water entry into the soil.
Hydrosol
(Australian Soil Classification) Soils that are saturated for >2 – 3
months in most years.
I
Included Soil Landscape
(Soil Landscape terminology) Small areas of other soil landscapes that
occur within another soil landscape but are too small to show at the
scale of mapping.
igneous
Rocks which have solidified from molten magma at or below the
earth's surface; grains are characteristically crystalline and
interlocking; crystal size decreases with increasing rate of cooling of
the molten rock material.
ignimbrite
Rock formed by the consolidation of pyroclastic material deposited by
ash flows.
illuviation
The process of deposition of soil material in the lower horizons of a soil
due to its removal from upper horizons through eluviation. Materials
deposited might include clay, organic matter, and iron and aluminium
oxides.
impermeable
Not permeable to water. See also permeability.
improved pasture
Cleared or lightly-wooded land with a ground cover of grasses and/or
legumes which are generally exotic species. Their grazing productivity
has been raised by cultivation and/or use of fertilisers.
in situ
A Latin term meaning ‘in place’. Normally applied to rocks, fossils and
soils which are situated where they were originally formed or
deposited. When used to describe soils, it usually refers to those
formed directly from or on bedrock.
incipient dune
The area at the rear of a beach where windborne sand accumulates
through colonisation by perennial and annual plants, eventually to form
a foredune.
Glossary of Terms used in Soil and Landscape Science
33
industrial land
Land supporting factories, warehouses, sawmills, refineries and their
environs or grounds used for the manufacture of products or goods.
infiltration
The downward movement of water into the soil. It is largely governed
by the structural condition of the soil, the nature of the soil surface
including presence of vegetation and the antecedent moisture content
of the soil.
inner barrier
Barrier characterised by subdued topography and well-developed soils
(Podzols). Considered to be Pleistocene in age and formed when sea
levels were higher.
inset terrace
An abandoned floodplain (i.e., terrace) that has a new floodplain inset
below it due to a fall in discharge. There is no downcutting into the
bedrock valley floor and both terrace and floodplain share the same
bedrock trench.
interbarrier swamp
Swamp or poorly-drained area that forms in the depression between
the inner and outer barriers. The swamp is longditudinal and parallel to
the coast. In many cases, a stream (i.e., interbarrier creek) is present
instead of a swamp.
interfluve
The area of land between two adjacent flowlines.
intergrade
Soils types showing traits of (usually) two Great Soil Groups.
intertidal flat
Large flat subject to frequent inundation by water that is usually salty
or brackish, aggraded by tides.
intrusion
A body of igneous rock which has been forced into older surrounding
country rocks but has cooled and lithified before reaching the earth’s
surface.
intrusive
Rock which, when fluid, has penetrated other rocks and solidified
before reaching the surface.
invasive native scrub
(Soil Landscape terminology) Refers to a range of native woody
species (trees and shrubs) which tend to thicken in density resulting in
a change of historic vegetation structure from grasslands or open
woodlands to tree or shrub-dominated landscapes. This is a
consequence of alteration of land use (including burning frequency),
climatic fluctuation and/or other factors. It results in changes to
pastoral productivity, habitat and landscape function.
invasive weeds
(Soil Landscape terminology) Plants that can substantially degrade
valuable land to an extent that requires remedial action. Weeds are a
serious threat to the natural environment and primary production. They
displace native species, contribute significantly to land degradation,
and reduce farm and forest productivity. Major invasions change the
natural diversity and balance of ecological communities. These
changes threaten the survival of many plants and animals because the
weeds compete with native plants for space, nutrients and sunlight.
Glossary of Terms used in Soil and Landscape Science
34
isohyet
A line on a map joining centres which receive equal amounts of
rainfall.
J
jarosite
Distinctive pale yellow deposits precipitated around old root channels
and on ped faces under strongly oxidising, severely-acid conditions in
acid sulfate soils. One of the most commonly used morphologic
features to identify acid sulfate soils, although it is not always present.
jasper
A translucent, impure form of quartz with red, brown or green
colouration.
Jurassic period
Geological period from 295 – 135 million years ago.
K
K factor
(Soil Landscape terminology) The Unifed Soil Loss Equation includes
a soil erodibility factor known as K (Wischmeier & Smith 1978). K
factor is a derived index of the susceptibility of a soil to sheet and rill
erosion. The formula that the Department of Environment and Climate
Change’s Interp software program used to derive K factor is the USLE
modified for Australian conditions and based on that used in SOILOSS
(Rosewell & Edwards 1988), with profile permeability modified to follow
that used by Soil and Water Conservation Society (1993). If field data
indicates the soil material is a moderately to strongly cemented pan,
Pan is printed. Similarly, if the soil has a USCS classification of Pt,
Peaty is printed. This is because cemented pans and peats are not
usually considered erodible and are beyond the range of USLE
parameters.
The percentages of silt and fine sand are derived from analyses of
non-dispersed fine earth particle size if they are available. Otherwise,
Interp defaults to results for the fine earth particle size. If the K factor is
<0.0001 or is negative, the K factor is presented as being zero.
Note: K factor alone has very limited value unless it is used in
conjunction with all other factors in USLE. See erodibility and erosion
hazard.
Kandosol
(Australian Soil Classification Soil Order) Soils other than Hydrosols
soils that have well-developed B
2
horizons in which the major part is
massive or has only a weak grade of structure and which has a
maximum clay content >15% in some part of the B
2
horizon.
karst
A pattern of unspecified relief and slope, typically with fixed deep
erosional stream channels forming a non-directional disintegrated
tributary pattern and many closed depressions without stream
channels. Eroded by continuously active solution and rarely active
collapse, the products being removed through underground channels.
Glossary of Terms used in Soil and Landscape Science
35
Typical elements are hillcrest, hillslope (dominant) and doline. Includes
summit surface, valley flat, plain, alcove, drainage depression, stream
channel, scarp, footslope and landslide, and talus.
Karst Soil Landscape
(Soil Landscape terminology) Soil landscapes dominated by solutional
processes, particularly on limestone and related rock types. Soil parent
materials include accumulations of less soluble minerals. Drainage
patterns are deranged and solution hollows are common. Landform
patterns may include tors, hillslopes and dolines.
Krasnozems
(Great Soils Groups classification) Deep, red strongly-structured clay
soils with clay content gradually increasing with depth and weak
horizon differentiation.
Kurosols
(Australian Soil Classification Soil Order) Soils with a clear or abrupt
textural B horizon and in which the major part of the upper 0.2 m of the
B
2
horizon (or the major part of the entire B
2
horizon if <0.2 m thick) is
strongly acid.
L
labile
A measure of weak plasticity used in a consistency test. The cube
fractures and fragments are easily deformed.
lacustrine
Unconsolidated surface material deposited mainly in standing water
such as lakes.
Lacustrine Soil
Landscape
(Soil Landscape terminology) Result from infilling of lakes with
sediments deposited in still water. Soil parent materials are usually
fine-grained, well-sorted and often varved. Ground surfaces are level
to gently inclined and slightly concave. Landform elements include
lakes, playas and some oxbows and lagoons.
lagoon
A closed depression filled with water that is typically salty or brackish,
bounded at least in part by forms aggraded or built up by waves or
reef-building organisms.
lake
Water-filled closed depression or a large or small body of water
surrounded by land, whether freshwater or brackish.
laminae
Thin sedimentary layers which are generally <5 cm thick.
laminate
Thinly-bedded, fine-grained sedimentary rock.
Land and Soil Capability,
LSC
A land capability classification that builds on the Rural Land Capability
(RLC) system developed in 1986 for NSW. It retains the eight classes
of the earlier system but places additional emphasis on specific soil
limitations and their management.
The LSC assessment scheme uses the biophysical features of the
land and soil to derive detailed rating tables for a range of land and soil
hazards. Each hazard is given a rating between 1 (best, highest
Glossary of Terms used in Soil and Landscape Science
36
capability land) and 8 (worst, lowest capability land), and the final LSC
class of the land is based on the most limiting hazard.
landform element
Part of the landform characterised by a distinctive slope, shape, size,
form and type of geomorphological process (e.g. aeolian, alluvial)
active on it. Typically, a landform pattern is formed from several
landform elements.
landform pattern
Broad descriptive classification of the landform typically assessed
within 300 m of the point of observation. Each landform pattern is
typically formed from several related landform elements.
landscape
That part of the land’s surface, generally extensive, being viewed or
under study, that relates to all aspects of its physical appearance,
including various vegetation associations and landforms. The
underlying geology and soils, and land use might influence the
character of a landscape.
landslide
Moderately inclined to very steep slope, eroded in the upper part and
aggraded in the lower part by water-aided mass movement,
characterised by irregular hummocks.
landslip
A general term used to encompass those landslides that are
composed mainly of soil and underlying weathered material, are
initiated by finite shear failure along one or more distinct slip facies and
move downslope for only relatively short distances. In many instances,
conventional soil conservation measures such as tree planting can be
applied to affect their control.
laterite
A soil in which an indurated iron-rich layer usually overlies a mottled
clay and a pallid clay.
Lateritic Podzolic Soil
(Great Soil Groups classification) The essential features of these soils
are strong texture contrast with thick, sandy A horizons overlying
mottled yellow-brown and red clay B horizons, an horizon of nodular
pisolitic, or massive ironstone in the base of the A
2
and upper B
horizon, a thick zone of coarsely mottled white, red and yellow clay
below the B horizon grading into dominantly white clay above the
kaolinised parent rock, and acid reaction throughout the profile (Stace
et al. 1968, p.344).
lattice gilgai
Discontinuous elongate mounds and/or elongate depressions at
approximately right angles to the contour. They usually occur on
sloping land and commonly between linear gilgai on lower slopes and
plains.
lava plain
Level to undulating with very low to extremely low relief typically with
widely spaced fixed erosional stream channels which form a
nondirectional, integrated or interrupted tributary pattern. Aggraded by
volcanism (lava flow) that is generally relict, it is subject to erosion by
continuously active sheet flow, creep, and channelled stream flow.
Typical elements are plain, hillslope and streambed.
leached earths
Soils like Earths, but with a distinct bleached near surface (A
2
) horizon.
Glossary of Terms used in Soil and Landscape Science
37
leaching
The removal in solution of the more soluble minerals and salts by
water seeping through a soil, rock, ore body or waste material.
lenticular
Soil particles are arranged around an elliptical or circular plane and are
bounded by curved faces with considerable accommodation to the
faces of surrounding peds; most vertices between adjoining faces are
angular and acute.
leucoadamellite
A lighter-coloured form of adamellite which contains 0 – 30% of dark
minerals.
leucocratic
A term describing light coloured igneous rocks i.e. rocks with <30%
dark-coloured minerals.
leucogranite
A lighter-coloured form of granite containing 0 – 30% of dark minerals.
levee
Very long, very low, nearly level sinuous ridge, immediately adjacent to
a stream channel, built up by overbank flow. Levees often occur in
pairs bounding the two sides of a stream channel at the level reached
by frequent floods; part of a covered plain. See also embankment.
lime
A naturally-occurring calcareous material used to raise the pH of acid
soils and/or supply nutrient calcium for plant growth. The term normally
refers to ground limestone (CaCO
3
) but may include processed forms
such as hydrated lime (Ca(OH)
2
) or burnt lime (CaO). The processed
forms are also effective for treating dispersible soils.
limestone
Non-clastic sedimentary rock consisting essentially of the carbonate
minerals calcite and dolomite; may be organic, detrital or chemically
precipitated.
linear gilgai
Long, narrow, parallel, elongate mounds and broader, elongate
depressions at approximately right angles to the contour. They usually
occur on sloping land. The vertical interval is usually <0.3 m and the
horizontal interval is usually 5 – 8 m.
linear shrinkage
Linear shrinkage is the decrease in length of a soil sample (rabbled
and sieved <0.425 mm) when oven-dried of the moisture content from
the liquid limit. Shrinkage is expressed as a percentage of the original
dimension. The method is described in Craze et al. (1993), Crouch et
al. (1991) and AS1289.C4.1-1977. Linear shrinkage is a relatively
tedious and expensive test that is done only on soils that are not
sands, and when dispersion is <50% or when volume expansion tests
fail to saturate or shrink. These conditions mask the relationship
between volume expansion and shrink-swell behaviour (Mills et al.
1980).
lithic sandstone
A detrital sedimentary rock with mainly sand-sized particles consisting
of rock fragments, quartz and feldspar set in a finer-grained matrix.
lithified
Newly-deposited sediments which have been compacted or cemented
to rock form.
lithofeldspathic
Containing abundant fragments of feldspar-rich rocks.
Glossary of Terms used in Soil and Landscape Science
38
Lithosol
(Great Soil Groups classification) A shallow soil showing minimal
profile development and dominated by the presence of weathering
rock and rock fragments. Lacking horizons other than an A
1
(one layer
only).
littoral complex
Mixed growth forms; mosaic of mangroves, low shrubs, forbs, sedges
and swamp grasses adjacent to estuarine or tidal areas.
loam
A medium-textured soil of approximate composition 10 – 25% clay,
25 – 50% silt and <50% sand. The bolus is coherent and rather
spongy; smooth feel when manipulated but with no obvious sandiness
or silkiness; may be somewhat greasy to the touch if much organic
matter present; will form ribbon of ~25 mm; clay content ~25%.
local relief
The difference in elevation between the high and low points of the
landscape.
localised occurrence
Relates to a soil or landscape hazard or quality which is confined to
certain elements of a soil landscape
loess
A blanket deposit of buff-coloured calcareous silt. It is homogeneous,
non-stratified weakly coherent, porous and friable. A rude vertical
parting allows it to stand in steep or vertical faces. Loess covers wide
areas in northern Europe, eastern China and the Mississippi Valley.
See also parna.
logged native forest
Stands of native forest which have been or are being commercially
logged.
loose
Incoherent mass of individual particles or aggregates forms the soil
surface. The surface is easily disturbed by pressure of forefinger.
low hills
Gentle to very steep slopes of low relief typically with fixed erosional
stream channels, closely to very widely-spaced, which form a
non-directional or convergent, integrated, tributary pattern. There are
continuously active sheet flow, creep and channelled stream flow.
Typical elements are hillcrest, hillslope (dominant), drainage
depression and stream bed. Includes footslope, alcove, valley flat,
gully, tor, summit surface, landslide and doline.
low shrubland
Canopy cover <30% and maximum height <2 m; sparse upper stratum
with a lower stratum of grasses and forbs.
lower order stream
Streams close to the source and with none too few tributaries.
lunette
Elongated, gently curved, low ridge, built up by wind on the margin of a
playa, or intermittent lake, typically with a moderately inclined
wave-modified slope towards the playa, and a gentle, outer slope
gradient.
Glossary of Terms used in Soil and Landscape Science
39
M
maar
A level-floored, commonly water-filled closed depression with a nearly
circular steep rim excavated by volcanism.
macropores
Spaces generally <2 mm in diameter in soil fabric.
made land
Where human activity has brought about severe disturbance to the
natural landscape features. It includes irrigation areas, reclaimed land
and restored mining areas. Typical elements are fill-top (dominant),
cut-over surface, cut face, embankment, berm and trench and include
mound, pit and dam.
magma
Molten fluid formed within the crust or upper mantle of the earth which
may consolidate to form an igneous rock. Magma which is extruded
onto the surface of the rock becomes lava.
mallee form, mallee habit
Growth form in a tree (usually Eucalyptus spp.) which has many stems
arising from its base.
manganic horizon
Horizon containing >20% (visual abundance estimate) of black
manganiferous nodules or concretions which are mostly uncemented,
and which has a thickness of ~0.1 m. Most nodules also contain some
iron.
manganiferous
Consisting of or containing oxides of manganese.
manganocrete
Manganiferous duricrust consisting of manganese dioxide (MnO
2
)
cemented talus deposits.
mangans
Coatings of manganese oxides or hydroxides. The material may have
a glazed appearance and is very dark brown or black.
mangroves
Shrub or small tree growing in salt (or brackish) water and
characterised by the presence of pneumatophores.
map area reference
Refers to a certain area (as opposed to a point) and is defined as the
last significant coordinates given in the map reference.
marble
Limestone which has been recrystallised by heat and pressure during
metamorphic processes.
marine plain
Plain eroded or built up by waves, tides or submarine currents and
raised above sea level.
marine sediments
Sediments transported and deposited by the sea.
Marine Soil Landscape
See Beach/Barrier Soil Landscape.
mass movement
Downslope displacement of unstable soil material on slopes. Its
occurrence depends on profile drainage, soil mineralogy and slope
Glossary of Terms used in Soil and Landscape Science
40
morphology. It might occur as a catastrophic event, e.g., mud slide,
landslide, or as a slow incipient process, e.g., creep.
mass movement hazard
(Soil Landscape terminology) Mass movement is a general term for
several forms of slope failure including rockfalls and earth creep,
slumps, slips and flows on steep, and often wet, slopes. Soil features
include shear planes, slickensides and colluvial materials. Mass
movement may lead to severe damage to buildings, roads and
services, or may result in recurrent problems such as shifting
foundations. Mass movement hazard is assessed by the abundance of
mass movement evidence.
massif
A section of the earth’s crust demarcated by faults or flexures that
tends to maintain its internal structure when displaced. Also refers to
the group of mountains formed by such a structure.
massive
The condition of a soil layer in which the layer appears as a coherent
or solid mass largely devoid of peds.
matrix
The smaller, grain-sized material that is typically a cementing agent
within a soil or rock in which larger particles are embedded. May also
be referred to as sulfuric materials.
meadow soils
Brownish-black organo-mineral surface soils with well-developed
structure becoming paler and less organic with depth. The watertable
is present for at least part of the year. See also normal meadow soils.
meander plain
A floodplain with widely spaced, rapidly migrating, moderately deep
alluvial stream channels which form a unidirectional integrated
non-tributary network. There are frequently active aggradation and
erosion by channelled streamflow with subordinate aggradation by
overbank streamflow. Typical elements are stream channel, scroll and
plain (dominant). Includes oxbow. See also alluvial plain; floodplain.
meandering
The natural winding of stream channels across their floodplain,
resulting from a complex geomorphological process and involving
erosion on the outside streambank and alluvial deposition on the
inside.
megaxenolith
Large rock fragments from a different type of rock that are imbedded in
a granitic rock.
melacic horizon
Same as melanic horizon but pH is <5.5 and there is no structure
requirement.
melanic horizon
Dark surface (black when moist) of near-surface horizon that has an
insufficient organic carbon to qualify as a humose horizon and has
little, if any, evidence of stratification. The pH is >5.5.
melonhole gilgai
Irregularly distributed large depressions usually >3 m in diameter, or
greatest dimension, subcircular or irregular and varying from closely
spaced in a network of elongate mounds to isolated depressions set in
an undulating shelf with occasional small mounds. Some depressions
Glossary of Terms used in Soil and Landscape Science
41
may also contain sinkholes. The vertical interval is usually >0.3 m and
the horizontal interval is usually 6 – 50 m. The surface is almost level.
mesotrophic
Soil with effective cation exchange capacity (eCEC) divided by 100 g
from 5 – 15 cmol(+)/kg clay.
Mesozoic era
Geological era comprising the Triassic, Jurassic and Cretaceous
periods, ranging from 225 – 70 million years ago.
metamorphic
Rocks that have been changed in their mineralogical, textural or small
scale structural compositions by the action of heat and/or pressure.
metamorphic complex
A combination of many types of rocks which have been
metamorphosed together.
metasediments
Partially-metamorphosed sedimentary rocks.
meteor crater
Rare; comprising a circular closed depression with a raised margin;
mainly of low to high relief and having a large range of slope values,
without stream channels, or with a peripheral integrated pattern of
centrifugal tributary streams. The pattern is excavated, heaved up and
built up by meteor impact. Typical elements are crater, scarp, talus,
footslope, plain, hillcrest and hillslope. See also crater.
mica schist
Schist formed under a higher metamorphic grade with an abundance
of micaceous minerals, and sometimes garnet.
microcline
(KAlSi
3
O
8
) The low-temperature form of potassium feldspar, commonly
found in granitic rocks.
microgranite
Medium-grained acid igneous rock having very similar mineralogical
and chemical properties to granite.
migmatic
Refers to mixing of rocks from two different sources to create a new
rock. This might occur when an invading granitic material reacts with a
pre-existing metamorphic rock.
mineralogy
The study of minerals.
Miocene epoch
Geological epoch, part of the Tertiary period, from 24 – 5.3 million
years before present. An epoch of the Neogene sub-period of the
Cenozoic era.
moderate pedality
The soil contains peds which can be identified but are not distinct.
Although not distinct in an undisturbed soil, peds are well formed and
evident. When displaced, 30 – 70% of the soil material consists of
peds (Northcote 1979).
molality
Molality is the number of moles of solute dissolved in one kilogram of
solvent. Notice the two key differences between molarity and molality:
1. Molality uses mass rather than volume and uses solvent instead of
solution.
2. Unlike molarity, molality is independent of temperature because
mass does not change with temperature. If you were to place 90
Glossary of Terms used in Soil and Landscape Science
42
grams of glucose (0.50 moles) in a flask and then add one kilogram of
water, then you would have a 0.50 molal solution. Molality is usually
denoted with lower case m, i.e., a 0.50 m solution.
molarity
Molarity is the number of moles of solute dissolved in one litre of
solution. For example, if you have 90 g of glucose (molar mass = 180
g per mole), then this is (90 g)/(180 g/mol) = 0.50 moles of glucose.
When you place this in a flask and add water until the total volume = 1
litre, you would then have a 0.5 molar solution. Molarity is usually
denoted with a capital M i.e. a 0.50 M solution. Recognise that molarity
is moles of solute per litre of solution, not per litre of solvent. As well,
recognise that molarity changes slightly with temperature because the
volume of a solution changes with temperature.
montmorillonite
Clay materials comprising a group of aluminosilicate minerals with a
2:1 expanding crystal lattice structure. They are reactive clays
generally with high shrink/swell potential and high cation exchange
capacity.
monzonite
Plutonic rock of orthoclase, plagioclase and <2% quartz; intermediate
between syenite and diorite.
morphology
Form and structure.
mottled horizon
Horizon in which mottle abundance is >10% (visual abundance
estimate) and the contrast between colours is distinct and prominent.
mottling
The presence of more than one soil colour in the same soil horizon,
not including different nodule or cutan colours
mound
A hillock built up by human activity.
mountains
Moderate to precipitous slopes of very high relief with fixed erosional
stream channels which are closely to very widely spaced and form a
non-directional or diverging integrated tributary network. There is
continuously active erosion by collapse, landslide, sheet flow, creep,
and channelled stream flow. Typical elements are hillcrest, hillslope
(dominant), streambed. Includes talus, landslide, alcove, valley flat,
scarp, cirque and footslope. See also hills; low hills; plain; rises.
mudstone
A fine-grained, dark-coloured sedimentary rock formed from lithified
mud; like shale but more massive.
mulch
A natural or artificial layer of plant residue or other material on the soil
surface which provides protection against erosion and aids plant
establishment mainly by reducing moisture loss. It may also increase
infiltration and minimise temperature fluctuations.
N
national/state parks
Land in government ownership for conservation and recreation
purposes which is generally in a relatively undisturbed condition.
Glossary of Terms used in Soil and Landscape Science
43
native vegetation
Indigenous pasture, bushland and/or timber species adapted to the
prevailing environmental conditions such as climate, soils and natural
grazing patterns.
native/voluntary pasture
Cleared or lightly-wooded land with a ground cover of grasses and or
legumes which are either native species or naturalised (self-sown)
exotic species.
nephelinite
Extrusive rock consisting of pyroxene and nepheline.
Neutral to Alkaline Peat
(Great Soil Groups classification) These peats can be black and highly
granular, dark brown and fibrous, or of some intermediate character
and range in depth from ~30 cm to many centimetres. Lenses of shells
and patches of soft carbonates sometimes occur irregularly within the
peat and occasionally on the surface.
nodulation
A process, often one of alternating soil moisture conditions, whereby
minerals are transported in solution and reprecipitated to form sub-
circular concretions.
nodule
Irregular rounded mineral aggregate; no concentric or symmetric
interior fabric but may have hollow interior; usually easily separated
from the soil matrix.
Non-calcic Brown Soil
(Great Soil Groups classification) Very like Red-brown Earths but
without an A
2
horizon. They have a carbonate-free solum and a neutral
to slightly alkaline (with lower base saturation) B horizon. They are
also generally thinner soils, 40 – 80 cm deep.
non-cohesive soils
(Soil Landscape terminology) Loose, sandy soils can be subject to
severe wind erosion, gully erosion and batter failure. Batters with
slopes >25% should be supported with retaining walls. Batters with
slopes <25% should be revegetated quickly.
normal gilgai
Irregularly distributed small mounds and subcircular depressions
varying in size and spacing. The vertical interval is usually <0.3 m, and
the horizontal interval is usually 3 – 10 m. The surface is almost level.
normal marsh soils
Grey topsoil becoming lighter with depth which is usually saturated
with water to the soil surface.
normal meadow soils
Meadow soils with a podsolised layer.
O
Oligocene epoch
Epoch of the Tertiary period, 38 – 22.5 million years ago.
olivene
Weatherable greenish silicate mineral common in basic rocks often as
phenocrysts.
Glossary of Terms used in Soil and Landscape Science
44
open-forest
Vegetation structure consisting of trees <30 m tall with a canopy cover
30–70% of ground area; dry understorey of smaller trees, shrubs and
herbs.
orchard/vineyard
Land used for production of fruit trees and/or vines.
Ordovician period
Geological period from 525 – 440 million years ago.
organic soils
(Soil Landscape terminology) Soils with large amounts of organic
carbon (generally >12% [Isbell 2002]) such as peats and sandy peats
are generally unsuitable for use as engineering materials because they
have low wet-bearing strength and their physical properties may be
subject to change through decay. They are generally well-structured
for plant growth and have high waterholding capacities; however, they
are often very acid and may require large quantities of lime and
nitrogen as well as other nutrients and trace elements for optimum
plant growth. Most topsoil contains sufficient organic matter to be
unsuitable for engineering purposes. Also, highly organic soil materials
located in swampy areas tend to suffer significant structural decline
when drained.
Organosols
(Australian Soil Classification) Soils not regularly inundated by saline
tidal waters and which have >0.4 m of organic materials in the upper
0.8 m either extending down from the surface or cumulatively or have
organic materials extending from the surface to >0.1 m depth directly
overlying rock or other hard layers.
orthoclase
(KAlSi
3
O
8
) A common rock-forming mineral of the feldspar group.
outcrop
The exposure at the surface of rock that is inferred to be continuous
with underlying bedrock.
outer barrier
Barrier characterised by the presence of sand dunes with moderate
relief and minimal or no soil development. Considered to be Holocene
in age and formed when sea levels generally reached their present
stage. Occurs on the seaward side of the barrier system.
overland flow (sheetwash)
Water flowing in a thin layer over the land surface. In a soil
conservation context, it is usually storm runoff and may lead to sheet
erosion.
ox-bow
Long, curved, commonly water-filled closed depression, eroded by
channelled stream flow, but closed due to aggradation by channelled
or overbank stream flow during the formation of a meander plain; the
floor may be aggraded by overbank stream flow, wind, and biological
(peat) accumulation.
oxidation
To combine with oxygen resulting in the removal of one or more
electrons from an atom or ion, or group of atoms. Oxidation is
important to the formation of acid sulfate soils by converting pyrite to
jarosite and sulfuric acid.
Glossary of Terms used in Soil and Landscape Science
45
P
pagoda
Rock formation formed from the different rates of weathering of
alternative layers of sandstone and ironstone. The rock formations
resemble beehives in general morphology.
pagoda
Lake extant during a prior geological period.
Palaeozoic era
Geological era 600 – 230 million years ago.
pan
Indurated and/or cemented soil layer that is denser and less
permeable than the layers above and below it and generally
impenetrable to plant roots.
parent material
The geologic material from which a soil profile develops. It may be
bedrock or unconsolidated materials including alluvium, colluvium,
aeolian deposits or other sediments.
parna
A deposit of dust (suspended windblown mineral material)
differentiated from loess by its higher clay content.
particle size analysis,
PSA
(Soil Landscape terminology) The laboratory determination of the
amounts of the different separates in a soil sample such as clay, silt,
fine sand, coarse sand and gravel. The amounts are normally
expressed as percentages by weight of dry soil and are determined by
dispersion, sedimentation, sieving, micrometry or combinations of
these techniques.
Size classes for soil fractions are based on the international scale
(cited in McDonald et al. 1990):
• Clay— <0.002 mm
• Silt— 0.002 – 0.02 mm
• Fine sand— 0.02 – 0.2 mm
• Coarse sand— 0.2 – 2 mm
• Gravel— 2 – <60 mm.
particle size analysis,
PSA, non-dispersed
(Soil Landscape terminology) Analysis of non-dispersed particle size is
very like conventional analysis of particle size of the fine earth fraction,
except that soils are not chemically dispersed, but are mechanically
shaken. Particle sizes therefore tend to be coarser than those
produced by conventional analysis of particle size. To estimate
erodibility (K values) of the USLE, Loch and Rosewell (1992)
recommend the use of non-dispersed particle size analysis.
Non-dispersed particle size analysis is usually adapted for soils that
are identified as being self-mulching and highly aggregated. Within
these soils, the differences between conventional and non-dispersed
particle size analyses are greatest.
Highly aggregated soils have a dispersion percentage of less than
10%, are very strongly structured and are usually sub-plastic (bolus
texture grade increases by at least two grades during working). When
not compacted, or smeared, highly aggregated soils behave in a
Glossary of Terms used in Soil and Landscape Science
46
similar manner to soils with much coarser particle gradings. For
example, when subjected to concentrated water flows, highly
aggregated sub-plastic polyhedral clays can be expected to erode in a
similar manner to angular fine gravels.
particle size analysis,
PSA, fine earth
(Soil Landscape terminology) The fine earth fraction of a soil is the
portion that is composed of particles <2 mm in diameter and does not
include gravel. It relates to the guides for field texture derived from
Northcote (1979), based on percentages of particle size, and to texture
triangle diagrams such as the one depicted in Hazelton and Murphy
(1992). Field texture is also influenced by sesquioxides, carbonates,
organic matter, clay mineral type, base saturation and cation
dominance. The relationship between fine earth particle size analysis
and field texture requires very careful interpretation. The fine earth
fraction is calculated for each soil. The formula is:
Fine earth fraction % = whole soil % × 100/(100 - gravel %)
Most soil test results are reported for the fine earth fraction unless
otherwise stipulated. Results that relate to the whole soil, including
coarse fragments, are referred to as being ‘rock-adjusted’.
pasture
Grasses, legumes and/or other herbage (i.e. vegetation) used or
suitable for the grazing of animals (e.g. livestock). The term includes
land covered by such herbage and used or suitable for grazing.
Annual/perennial pasture consists largely of annual/perennial grasses
and/or legumes respectively. See also improved pasture;
native/voluntary pasture.
peat
Accumulation of partially decayed organic material. Varies in the level
of decomposition of the material and its content of mineral soil
particles.
peaty horizon
A surface or near-surface layer of organic materials >0.2 m thick
overlying mineral soil. It does not qualify as an Organosol.
Peaty Podzol
(Great Soil Groups classification) Soils consisting essentially of some
depth of acid fibrous peat or sandy peat overlying sandy mineral soil
that has most of the features of humus podzols but generally lacks a
distinct A
2
horizon.
ped
An individual, natural soil aggregate. See also dominant peds.
ped shape
Refers to the shape of natural soil aggregates. See also platy;
lenticular; prismatic; columnar; polyhedral; angular blocky; sub-angular
blocky; granular.
pedal
Describes a soil in which some, or all, of the soil material occurs in the
form of peds in the moist state.
pedality
Refers to the relative proportion of peds in the soil (as strongly pedal,
weakly pedal or non-pedal).
pediment
Gently inclined to level feature of extremely low relief; usually with
numerous, rapidly migrating, very shallow, incipient stream channels
which form a centrifugal to diverging integrated reticulated pattern.
Glossary of Terms used in Soil and Landscape Science
47
Underlain by bedrock, eroded and locally aggraded by frequently
active channelled stream flow or sheet flow with subordinate wind
erosion. Characteristically lies downslope from adjacent hills with
markedly steeper slopes. A typical element is a plain streambed. See
also
sheet-flood fan; alluvial fan.
pediplain
Level to very gently inclined landform pattern with extremely low relief
and no stream channels, eroded by barely active sheet flow and wind.
Largely relict from more effective erosion by streamflow in incipient
stream channels as on a pediment. A typical element is a plain.
pelite
An aluminium rich rock formed through metamorphism of clay-rich
sediments.
peneplain
Level to gently undulating landform pattern with extremely low relief
and sparse, slowly migrating stream channels which form a non-
directional integrated tributary pattern. It is eroded by barely active
sheet flow, creep, and channelled and overbank stream flow. Typical
elements are plain (dominant) and stream channel.
perched watertable
The surface of a local zone of saturation held above the main body of
groundwater by an impermeable layer, usually clay, and separated
from it by an unsaturated zone.
periodically frozen soil
(frost action potential)
(Soil Landscape terminology) Frost action potential is a rating for the
susceptibility of the soil to upward or lateral movement by the
formation of segregated ice lenses. It rates the potential for frost heave
and the subsequent rapid loss of soil strength when the ground thaws
and the ice crystals and lenses within the soil melt. Unequal heaving
and subsidence upon thawing can crack or tip concrete slabs. In
Australia, this hazard is generally recognised by the presence of large
ice crystals in topsoils. Although most soils in Australia have zero frost
action potential, a few colder areas may exhibit low frost action
potential where damage to buildings and roads is unlikely, but still a
possibility (Soil Survey Staff 1993).
permanent wilt point,
PWP
(Soil Landscape terminology) Permanent wilting point arbitrarily
represents the amount of soil moisture remaining when plant foliage
begins to die due to moisture stress (McIntyre 1974). It is generally
accepted to be equivalent to soil water content at a suction of 1.5 MPa,
although the level varies between plant species, with desert species
often surviving at much lower levels.
Gravimetric water content is converted to volumetric water content by
multiplication of soil bulk density. If bulk density is not available, it is
assumed to be 1.4. Permanent wilting points are not generally affected
by sample handling.
Soils with a high permanent wilting point contain a relatively large
percentage of water when plants start to wilt due to drought. Dry soils
with low permanent wilting points require less water (less rainfall after
a prolonged dry spell) for plants to begin to regrow.
Glossary of Terms used in Soil and Landscape Science
48
permanently high water
tables
(Soil Landscape terminology) Problems often occur where water tables
are permanently within 2 m of the surface. The surface soil materials
may dry out, but sub-surface soils are often saturated. In these soils,
for example, septic effluent disposal often results in groundwater
pollution
permeability
The measure of a profile’s potential to transmit water (saturated
hydraulic conductivity, K
s
or K
sat
). An intrinsic property of the soil
profile, independent of climate and drainage, it is controlled by the
least permeable layer in the profile. It is inferred from attributes of the
soil such as structure, texture, porosity, cracks and macropores, and
shrink-swell properties.
permeability, high
(Soil Landscape terminology) Soils that drain water quickly. They
usually have coarse textures (sands) and many interconnecting pores.
They are not suitable for absorbing effluent from septic systems
because liquid drains rapidly into the groundwater where it can cause
pollution and potential health problems elsewhere. Soils with high
permeability often have low waterholding capacities. Seedlings and
newly established plants require regular, light irrigation.
permeability, low
(Soil Landscape terminology) Soils that usually have very slow
drainage and are likely to pond water for long periods. They usually
have clayey textures and mottled or greyish colours. They are not
suitable for absorbing effluent. Special drainage may be required. They
may also be sodic and have low wet bearing strengths.
Permian period
Period of geological time, 225 – 280 million years before present.
petroferric horizon
Ferruginous or ferromanganiferous nodules or concretions cemented
in place into indurated blocks or large irregular fragments.
petrology
The study of the natural history of rocks.
petroreticulite horizon
Reticulate horizon that is always indurated in the greater part both
before and after exposure.
pH
A measure of the acidity or alkalinity of the soil. A pH of 7.0 denotes
neutrality. Higher values indicate increasing alkalinity and lower values
indicate increasing acidity. The scale is logarithmic, i.e., a pH of 4.0 is
10 times more acidic than a pH of 5.0.
In soil landscape reports the following ranges have been used:
• <3.5— extremely acid
• 3.6 – 4.5— strongly acid
• 4.6 – 5.5— moderately acid
• 5.6 – 6.5— slightly acid
• 6.6 – 7.5— neutral
• 7.6 – 8.5— slightly alkaline
• 8.6 – 9.5— moderately alkaline
• 9.6 – 10.5— strongly alkaline
• >10.5— extremely alkaline
Glossary of Terms used in Soil and Landscape Science
49
pH 1:5 soil:0.01M CaCl
2
(pH CaCl
2
)
(Soil Landscape terminology) This is the activity of the negative
logarithm (base 10) of the number of hydrogen ions in a suspension of
1:5 soil:0.01M CaCl
2
. This test method is considered to approximate
average soil solution calcium and salinity levels (Russell 1973).
Conyers and Davey (1988) found that pH in 1:5 soil:0.01M CaCl
2
is
usually 0.5 to 1.0 units less than pH in 1:5 soil:water except in saline
and some variable charge soils where the difference may be smaller
(Russell 1973). 0.75 pH units are added to pH values in 1:5 soil:0.01M
CaCl
2
to approximate pH in 1:5 in soil:water. pH in 1:5 soil:0.01M
CaCl
2
is not appropriate for soils rich in calcium carbonate.
pH 1:5 soil:water (pH
H
2
O)
(Soil Landscape terminology) This is the activity of the negative
logarithm (base 10) of the number of hydrogen ions in a suspension of
1:5 soil:water. It is the de facto standard pH measurement for most soil
test interpretations; however, pH measured in 1:5 in soil:water is
sensitive to seasonal variations in the pH of soil solutions.
pH buffering capacity,
expected
(Soil Landscape terminology) pH buffer capacity is the amount of acid
input required to reduce pH by one unit. It is not measured directly, but
is derived from the regression equation presented in Helyar et al.
(1990). Expected buffer capacity should not be used to directly
calculate lime requirements, nor the rate of acidification. Instead,
expected buffer capacity can be used to compare the relative
resistance to increase in acidity of different soil types.
phenocrysts
Large crystals set in a fine-grained ground mass.
phyllite
A fine-grained low-grade regionally metamorphosed sedimentary rock
intermediate in grade between a slate and a schist. They typically have
a distinctive shiny surface caused by the reorientation of mica minerals
along cleavage planes.
pisolitic
Spheroidal concretions cemented together.
pit
A closed depression excavated by human activity. This term usually
relates to mining or quarrying.
plagioclase
A commonly found series of feldspars varying in composition from
NaAlSi
3
O
8
to CaAl
2
Si
2
O
8
.
plain
Level to undulating or, rarely, rolling landform pattern with extremely
low relief (<9 m). See also mountains; hills; low hills; rises.
planeze
That stage in the erosion of shield volcanoes wherein dwindling
sectors of the constructional surfaces (planezes) survive on the ridges
between deeply eroded major consequent valleys (Cotton 1944).
plant available
waterholding capacity,
PAWC
(Soil Landscape terminology) PAWC is the amount of water available
to plants from when the soil stops draining water to when the soil
becomes too dry to prevent permanent wilting.
PAWC is calculated by subtracting permanent wilting point from field
capacity; therefore, it is influenced by the same sampling effects as
Glossary of Terms used in Soil and Landscape Science
50
field capacity. Field capacity >100% can occur when there is a high
clay content, high shrink-swell potential and/or high organic matter.
Soils with a high PAWC can store larger amounts of soil water for plant
growth, and need watering less often, compared to soils with a low
PAWC. Rankings are based on volumetric ratings of United States
Department of Agriculture (1983) for Udic (humid-adequate moisture)
and Ustic (semi-humid semi-arid) soil moisture regimes of United
States Department of Agriculture Soil Taxonomy (Soil Survey Staff
1975).
plant available
waterholding capacity,
PAWC, swelling soils
adjustment
Swelling soils in the field are confined by the material above, below
and around them. This limits the potential for a soil to swell and to
absorb water.
In laboratory testing, soil materials are unconfined and swell to their full
potential. Laboratory samples tested are based on crushed and sieved
material. These factors combine to over-estimate field capacity and
plant available waterholding capacity for swelling soils. Errors may be
compounded by bulk density estimates. In such soils, test results
should be applied with caution.
plant available
waterholding capacity,
PAWC, rock and salt
adjustment
Rock adjusted (RA) PAWC: it is assumed that rocks do not contribute
to PAWC.
Salt adjusted (ECe) PAWC: a major physiological effect of salinity is to
reduce the available water for plants by increasing the osmotic
pressure in soil and thus increase the permanent wilting point. Salinity
further reduces rock-adjusted PAWC by ~25% for each 4 dS/m of ECe
(United States Department of Agriculture 1983).
plant available
waterholding capacity,
PAWC, low
(Soil Landscape terminology) Soil materials with low available
waterholding capacity can store only limited amounts of water that can
be extracted by plants. Plants growing in these soils require small and
frequent applications of water for optimum growth. PAWC is of
greatest importance in areas with seasonal rather than regular or
highly unreliable rainfall. PAWC ratings in soil test results are:
• very low (<5)
• low (5 – 10)
• moderate (10 – 15)
• high (15 – 20)
• very high (>20).
In the ‘Soil limitations for each soil material’ table (if included) the
rating of low PAWC is more broadly defined as <10.
plastic
Describes soil materials which are in a condition that allows them to
undergo permanent deformation when force is applied without
appreciable volume change or elastic rebound or without rupture.
plasticity
(Soil Landscape terminology) Plastic state occurs at water contents
where soils deform or change shape without change in volume. It
occurs between the semi-solid (crumbly) and liquid state and is defined
as the difference between the plastic and liquid Atterberg limits (Hicks
1991). A soil with high plasticity has plastic properties over a wide
range of moisture contents.
Glossary of Terms used in Soil and Landscape Science
51
Highly plastic soils are typically high in clay content and deform easily
when mechanically stressed in the moist to saturated state. They are
often tough and hard when dry, do not support loads well and have
poor trafficability when wet. Soils with no or low plasticity change from
solid to liquid with little change in moisture content and may be prone
to mass movement (Hazelton & Murphy 1992). Highly plastic soils can
be very sticky, are unsuitable for foundations and usually have low wet
bearing strengths and high shrink-swell potential.
• Highly plastic (HP) soils— USCS classifications of CH-CL, OH-
CL, CL-OH, Pt, CH-OH, OHCH, CH and MH.
• Moderately plastic (MP) soils— USCS class of CL-CH, CL, and
OH.
• Low plasticity (LP) soils— USCS classes CL-ML, ML-CL, ML, CL
and OL.
• Non-plastic (NP) soils— all other USCS categories and are sandy
or gravelly.
plateau
Level to rolling landform pattern with plains, rises or low hills standing
above a cliff, scarp or escarpment that extends around a large part of
its perimeter. A bounding scarp or cliff may be included or excluded; a
bounding escarpment would be an adjacent pattern. Typical elements
are plain, summit surfaces and cliff. Includes hillcrest, hillslope,
drainage depression, rock flat, scarp and stream channel.
platy
Soil peds are arranged around a horizontal plane and bounded by
relatively flat horizontal faces with accommodation to the faces of
surrounding peds.
playa
A shallow, closed depression flooded intermittently and, at other times,
displaying a surface salt or mud.
playa plain
Level landform pattern with extremely low relief, typically without
stream channels; aggraded by rarely active sheet flow and modified by
wind, waves and soil phenomena. Typical elements are playa, lunette
and plain.
Pleistocene epoch
First epoch of the Quaternary period, 2 million – 10,000 years before
present.
pluton
A body of igneous rock formed beneath the surface of the earth by the
cooling and solidification of magma.
plutonic rocks
Igneous rocks (e.g. granite) which have cooled and solidified at great
depth.
podosol diagnostic
horizon
Various B horizons consisting of alluvial accumulations of amorphous
organic matter-aluminium and aluminium-silica complexes with or
without iron in various combinations.
Podosol
(Australian Soil Classification) Soils with B horizons dominated by the
accumulation of compounds of organic matter, aluminium and/or iron.
Glossary of Terms used in Soil and Landscape Science
52
Podzol
(Great Soil Groups classification) Acid sandy soils with strongly
differentiated horizons including a bleached horizon above a coffee-
coloured pan and coloured subsoil.
point bar
Elongated, gently to moderately inclined low ridge within the stream
channel built up by channelled streamflow.
polyhedral
Soil peds are arranged around a point and bounded by more than six
relatively flat, unequal, dissimilar faces. Re-entrant angles between
adjoining faces are a feature. There is usually considerable
accommodation of ped faces to the faces of surrounding peds. Most
vertices are angular.
polymictic
A term used to describe conglomerates whose constituent gravels,
stones and cobbles originate from many different rock types and
compositions.
poor moisture availability
(Soil Landscape terminology) When moisture availability is low, soil is
referred to as being droughty. These soils have very limited soil water
storage in comparison with other soils in the same climate zone. Freely
draining soils or shallow soils, particularly those that do not receive
run-on or allow easy entry of water to plant roots, are prone to drought.
poor seedbed conditions
(Soil Landscape terminology) Surface soil materials with properties
that create difficulty in preparing adequate seedbed conditions, may be
naturally cloddy, hard-setting, sandy, sodic or dispersible. Poor
seedbed conditions are associated with the following soil contents:
very low organic matter, very high or low clay, and high silt and fine
sand.
porosity
The degree to which the soil mass has interconnected pores or
cavities, generally expressed as a percentage of the whole volume of a
soil horizon which is unoccupied by solid particles. It influences soil
drainage characteristics.
porphyritic
A term which describes igneous rocks containing relatively large
crystals set in a finer grained material (or groundmass).
porphyry
Rock containing conspicuous phenocrysts (large crystals) in a fine-
grained matrix.
potential acid sulfate soils
Soil material which is waterlogged and contains oxidisable sulfur
compounds, usually ferrous iron disulfide (pyrite, FeS
2
) which has a
field pH of ≥4 (1:5 soil:water) but will become severely acid when
oxidised. May also be referred to as sulfidic materials. See also actual
acid sulfate soils.
Potential/known discharge
areas
(Soil Landscape terminology) Occur where water tables are liable to
approach or contact the ground surface and become springs. When
this occurs, the ground often becomes wet or boggy and may become
saline and quickly erode to form scalds.
Potential/known recharge
areas
(Soil Landscape terminology) Areas with highly permeable, generally
non-saline soils and fractured geology can allow infiltration to
Glossary of Terms used in Soil and Landscape Science
53
contribute to underground water tables. Recharge areas may need
special long-term management strategies, crop rotations or plantings
to prevent rising water tables and salinity elsewhere.
physiographic region
A region with similar geological and topographic patterns and climate.
Prairie Soils
(Great Soil Groups classification) Moderately deep, mildly acid to
mildly alkaline soils with thick, dark, moderately-structured topsoils.
Principal Profile Form,
PPF
The end-point of the Factual Key soil classification system (Northcote
1979). A PPF code, e.g., Ug5.16, Gn2.23 or Dy3.41, describes the soil
profile to an extent where it is possible to make a reasonably concise
statement about its characteristics. An extended PPF may include
further information describing the surface soil in more detail and/or
material below the solum.
prior stream
Long, generally sinuous low ridge built up from materials originally
deposited by channelled stream flow along the line of a former stream
channel; may include a depression marking the old stream bed and
relict levees.
prismatic
Soil peds are arranged around a vertical axis and are bounded by well-
defined, relatively flat faces with considerable accommodation to the
faces of surrounding peds; vertices between adjoining faces are
usually angular.
Proctor Maximum
Compaction Test
This test measures the level of soil compaction achieved with a
standard compactive effort at a range of moisture contents. It provides
a guide for the optimum moisture content for compaction.
productive arable land
(Soil Landscape terminology) Areas of highly productive arable or
productive horticultural land are relatively rare within NSW and have
long-term value. Special planning consideration should be given to
degradation, sterilisation or alienation of potentially highly productive
land by inappropriate land use, tenure or zoning. Productive arable
land is a physical land assessment and does not consider additional
social and economic factors used to determine prime agricultural land.
Prime agricultural land is identified as Class 1, 2 and 3 land on
Agricultural Land Classification Maps (Hulme et al. 2002) produced by
the NSW Department of Primary Industries.
profile
A column of soil extending downwards from the soil surface through all
its horizons to parent material, other substrate material or to a
specified depth (McDonald et al. 1990). Each profile is uniquely
identified by its number and the geographic location of its site. Soil
profiles are grouped into larger parent entities called surveys. Every
survey has its own unique name and number.
pyrite, pyrites
The cubic crystalline form of ferrous disulfide (FeS
2
); the most
common sulphide mineral.
pyroclastic
Term used to describe rocks consisting of fragmental material which
has been blown into the atmosphere by the explosive activity of
volcanoes.
Glossary of Terms used in Soil and Landscape Science
54
Q
quarrying/mining land
Land used for extractive industries, e.g., for gravel, sand, coal, metals
or minerals, also includes associated uses such as spoil dumps,
infrastructure and rehabilitated former mining/quarrying areas.
quartz
(SiO
2
)
The most common silica mineral.
quartz sandstone
A detrital sedimentary rock with mainly sand-sized quartz particles
cemented by silica or carbonates, and with little fine-grained matrix
material.
quartzite
Regionally or thermally metamorphosed rock in which quartz is the
primary constituent; grains have recrystallised into an interlocking
mosaic texture with little or no trace of cementation.
quartz-lithic sandstone
A detrital sedimentary rock with mainly sand-sized particles consisting
of rock fragments, quartz and feldspar set in a finer-grained matrix.
Quaternary period
Period of geological time from 2.6 million years ago to the present,
covering the Holocene and the Pleistocene epochs.
R
rainforest
Wet forest in which mesophytic species dominate. Tree species
diversity is high and canopy cover is 70 – 100%. Emergents, lianas,
ferns and epiphytes are usually present. Eucalypts, when present, are
usually canopy emergents.
rangeland
Land used for extensive grazing of sheep, cattle or other domestic
stock. Rangeland vegetation is typically native or naturalised pasture.
The area, in general, is often considered to receive insufficient rainfall
to support the economic production of crops on a regular basis, and
will generally support only low stocking densities.
reactive soil
A term used in the construction industry to describe a soil that changes
volume (shrink-swell) with changes in moisture content. This can
damage foundations.
rectilinear
Straight-sided. When used to describe a hillslope, this describes a
slope that is essentially straight in cross-section with little or no
convexity or concavity.
Red and Brown Hardpan
Soil
(GSG classification) These soils have simple, shallow to moderately
deep profiles of red earthy and massive soil sharply overlying an
indurated pan resulting from silica cementation and clay deposition.
Red Calcareous Soil
See Grey-brown and Red Calcareous Soil.
Glossary of Terms used in Soil and Landscape Science
55
Red Clay
See Grey, Brown and Red Clay.
Red Earth
(Great Soil Groups classification) Massive, reddish sandy profiles with
a gradual increase in clay content with depth over a diffuse to gradual
boundary.
Red Podzolic Soil
(Great Soil Groups classification) Strongly-differentiated duplex soils
with light to medium textured A
1
horizon over a pale or bleached A
2
over a reddish, firm to friable B horizon with generally polyhedral
structure.
Red-brown Earth
(Great Soil Groups classification) The characteristic features of these
soils are grey-brown to red-brown loamy A horizons, weakly structured
to massive, an abrupt to clear boundary between A and B horizons,
and brighter brown to red clay B horizons with well-developed medium
prismatic to blocky structure.
regolith
Mantle of loose and weathered material overlying the bedrock.
relict landform
Landform in which the formative geomorphological processes are no
longer active.
Rendzina
(Great Soil Groups classification) Shallow to very shallow soils formed
from limestones and marls. Usually they are black, very dark brown or
dark grey clay loams or light clays of strong, very fine crumb to
granular structure and loose, soft consistency which usually continues
throughout their thin sola.
residential development
A level of urban development which provides for the construction of
roads, drainage and services to cater for subdivision allotments for
housing, typically 400 – 5,000 m
2
.
residual
In situ processes of weathering, leaching and new mineral formation
are dominant. Lateral surface movement is minimal. A residual site
may occur either on low gradient topography, such as a plateau
surface, or where soil material is of such a nature as to resist lateral
movement despite a considerable slope gradient (Paton 1978).
Residual Soil Landscape
(Soil Landscape terminology) Soil landscapes dominated by sites
where deep soils have formed from in situ weathering of parent
materials. Residual soil landscapes typically have level to undulating
elevated landforms. Landform elements include some summit
surfaces, plateaux, terrace plains, peneplains and old ground surfaces.
Stream channels are usually poorly defined
retaining wall
A barrier, usually of uniform thickness and constructed or masonry
materials designed and installed to hold back unconsolidated rock
and/or soil. Its aim is to counter the gravitational force of the material it
is retaining and prevent mass movement. Small holes or gaps
(weepholes) may be incorporated in the wall to cater for seepage of
water.
reticulate horizon
Intended for strongly-developed reddish, yellowish and greyish or
white, generally reticulately-mottled horizons that can be hand-augured
Glossary of Terms used in Soil and Landscape Science
56
or cut with a spade. Ferruginous nodules or concretions may be
present.
rhyodacite
Fine-grained equivalent of granodiorite.
rhyolite
Fine-grained porphrytic acidic extrusive igneous rock; exhibits flow
texture; consists of quartz and feldspar in a glassy to cryptocrystalline
groundmass.
rich fen peats
Soils in which the profile is dominated by peat/organic matter resting
on silts to gravels.
ridgeslope
Slope along a ridge line.
rill, rill erosion
Removal of soil from the land surface by the formation of numerous
small channels <0.3 m deep. It typically occurs on recently cultivated
or disturbed soil. Sheet erosion grades into rill erosion or, where very
severe, into gully erosion. It is very difficult to assess rill erosion unless
the site is observed immediately after the erosion event as the rills are
eventually lost due to revegetation or cultivation and the evidence
indicates a sheet process. Indicators include rill frequency and depth,
lack of topsoil layer and exposure of subsoils or roots. Local
knowledge of an area is necessary for correct interpretation.
ring dyke
An igneous intrusion in which the individual members appear as
circular or part-circular outcrops. Ring dykes are usually taken to
indicate subsidence of the central block, e.g., a volcanic plug.
ripe
Describes wet sedimentary material that has dried out, supports roots
and has developed some structure and firm consistency.
ripeness
Describes the stages of the drying of wet sediments to soil. See also
ripe; unripe.
rises
A landform pattern comprising very gentle to steep slopes with very
low relief. The fixed erosional stream channels are closely to very
widely spaced and form a non-directional to convergent, integrated or
interrupted tributary pattern. The pattern is eroded by continuously
active to barely active creep and sheet flow. Typical elements are
hillcrest, hillslope (dominant), footslope and drainage depression.
Includes valley flat, stream channel, gully, tor and fan. See also
mountains; hills; low hills; plain.
river capture
The action of a river in acquiring the headstreams of a second river by
enlarging its drainage area at the expense of the other.
road subgrade rating
(Soil Landscape terminology) The capability of the soil material as
either in situ or consolidated imported material for use as road
subgrade. Road subgrade should be readily excavated, graded and
compacted and be sufficiently strong to support traffic loads. Road
subgrade is usually overlain by road base and then covered by a water
shedding surface pavement.
roadside erosion
Soil erosion associated with the presence of a road across a
landscape. Such may be directly caused by the road, or may be
Glossary of Terms used in Soil and Landscape Science
57
existing erosion aggravated by the location, nature and construction of
the road.
rock flat
A flat of bare consolidated rock usually eroded by sheetwash.
rock platform
A flat of consolidated rock eroded by waves.
rockfall hazard
(Soil Landscape hazard) Areas immediately below cliffs and unstable
scarps are at risk of serious damage from rockfalls and other mass
movement of debris. The presence of a rockfall hazard is assessed by
proximity to cliffs, scarps and other potentially unstable hillslopes as
well as the presence of unconsolidated scree and talus materials.
rock outcrop
(Soil Landscape terminology) Rock outcrop restricts excavation and
the installation of underground services. Garden establishment is often
difficult where there is rock outcrop
root ball
Soil profile and substrate encompassed by the roots of a tree which
has fallen over, due to natural or human causes.
rough-ped fabric
Peds are evident. Characteristically >50% of the peds are matt or
rough-faced.
Rudosol
(Australian Soil Classification) Soils with negligible pedologic
organisation. They are usually young soils in the sense that the soil
forming factors have had little time to pedologically modify parent rocks
or sediments. The component soils can vary widely in terms of texture
and depth. Many are stratified and some are highly saline.
runoff
Surface water running off the soil surface. The quantity of runoff
flowing off a site is largely determined by slope, surface cover and soil
infiltration rate.
run-on
Surface water flowing onto an area due to rainfall and runoff occurring
higher up a slope. Often occurs in an urban context as a contributing
factor to increased erosion hazard. Also used in semi-arid areas to
refer to surface water which is diverted from sloping country onto flatter
land to achieve increased production from such land. Areas with high
run-on are often prone to temporary localised flooding.
Run-on is ranked as:
• low— small volumes of overland flow occur
• moderate— significant overland flow occurs
• high— concentrated large volumes of overland flow occur.
rural capability
(Soil Landscape terminology) The ability of an area of land to sustain
permanent agricultural or pastoral production without permanent
damage. Land that is used beyond its rural capability will deteriorate
rapidly, resulting in loss of production and a permanent loss of soil
resources (Emery 1985).
General rural land capability classifications are provided for those soil
landscapes where most of the land has not been urbanised or
reserved as a National Park or nature reserve. Rural land capability
has been ranked by the severity of the limitations that are likely to
affect regular cultivation and grazing practices. Three degrees of
Glossary of Terms used in Soil and Landscape Science
58
severity of limitations are used for regular cultivation and for grazing.
They are low, moderate, and high (to severe).
Cropping
• Low limitations for regular cropping— a stable and productive land
surface can be maintained in cropping systems (including
minimum or no-till farming practices, stubble retention and
rotational cropping) where consideration is given to maintaining
and improving soil structure and nutrient status. Besides strip
cropping in some circumstances, no other special soil
conservation practices are necessary.
• Moderate limitations for regular cropping— soil conservation
measures such as graded banks, waterways, diversion banks and
contour cultivation are required to maintain surface stability and
productivity. Further, cropping systems should incorporate
minimum or no-till farming practices that include stubble retention
and rotational cropping, with attention paid to soil structure and
nutrient status.
• High to severe limitations for regular cropping— due to the
severity of limitations present, land is not suitable for cropping and
should be avoided.
Grazing
• Low limitations for grazing— simple soil conservation practices
such as pasture improvement, grazing pressure control, vermin
control, application of seed, fertilisers and contour chisel
ploughing are necessary to maintain a stable land surface.
• Moderate limitations for grazing— soil conservation measures
such as graded banks, diversion banks, gully control structures as
well as pasture improvement, controlled grazing pressure, vermin
control, application of seed and fertiliser and contour chisel
ploughing may be needed to maintain a stable land surface.
• High to severe limitations for grazing— land is generally best
suited for green timber. Livestock should be excluded.
Rural Capability
Classification
A method of land classification which ranks land by its ability to sustain
various intensities of rural land use.
Rural Land Capability,
RLC
An eight-class system used by the Soil Conservation Service of New
South Wales for evaluating rural land. It is based on an assessment of
the biophysical characteristics of the land, the extent to which these
will limit a certain land use, and the current technology that is available
for the management of land.
The classification also incorporates an assessment of the soil erosion
hazards, with emphasis on a `safe' level of land use, thus avoiding
environmental problems caused by soil erosion and sedimentation.
The capability classes categorise the land in terms of its general
limitations. Specific numerical values for individual limitations such as
climate, slope gradient, landform types, adverse soil conditions, rock
outcrop, drainage and inundation and productivity of crops etc. are not
given. Instead, the classification outlines the types of land uses
appropriate for a certain area of land and the types of land
Glossary of Terms used in Soil and Landscape Science
59
management practices needed to prevent soil erosion and maintain
the productivity of the land.
rural residential
development
A level of rural development which enables the construction of roads,
drainage and services to cater for subdivision allotments typically
2 – 10 ha in size.
rural residential land
Primarily residential land often associated with hobby farming.
Allotments are generally 1 – 15 ha in size.
S
saline discharge
Underground saline water which flows or seeps out at the soil surface.
Salinity can be concentrated by subsequent evaporation.
saline scalds
The removal of topsoil which exposes a subsoil naturally high in salts.
saline soil
A soil which contains sufficient soluble salts to adversely affect plant
growth and/or land use. Generally, a level of electrical conductivity of a
saturaltion extract >4 mS/cm at 25
o
C is regarded as the defining
characteristics of a saline soil.
salinity
(Soil Landscape terminology) The concentration of soluble salts in
water and soil assessed by measurement of electrical conductivity.
Excessive salt is toxic to most plants. Saline surface soils are usually
bare or have sparse plant cover. These soils have a high erosion
hazard and are often poorly drained. Treatment of saline soils often
involves removal of saline water by drainage and deep ripping as well
as establishment of salt-tolerant plant species. Cover crops, mulches
and large applications of nitrogenous fertilisers, as well as gypsum, are
often required for successful establishment of vegetation. To further
reduce concentrations of salts within the root zone of plants, measures
such as tree or lucerne planting in recharge areas may be required to
ensure long-term rehabilitation. Saline soils may be corrosive to
untreated underground services.
salinity, dryland or
irrigated
(Soil Landscape terminology) Excessive salt is toxic to most plants.
Saline surface soils are usually bare or have sparse plant cover. These
soils have a high erosion hazard and are often poorly drained.
Treatment of saline soils often involves removal of saline water by
drainage and deep ripping as well as establishment of salt-tolerant
species. Cover crops and mulches, as well as the application of
fertilisers and gypsum, are often required for successful vegetation
establishment.
Strategic measures that further reduce the concentration of salts within
the plant root zone (such as reduction of fallow ground and the
planting of trees or other deep-rooted perennials in recharge areas)
should be planned to ensure long-term rehabilitation. Saline soils may
be corrosive to untreated underground services. Saline sites have soils
with electrical conductivities >4 dS/m in the root zone.
Glossary of Terms used in Soil and Landscape Science
60
saltmarsh
A grassland or herbland occasionally inundated by sea water and
hence having salt tolerant plant species.
sandplain
Level to gently undulating plain of extremely low relief and without
channels. Formed possibly by sheet flow or streamflow but now relict
and modified by wind action.
sandy fabric
A soil material consisting of closely-packed sand grains which are
weakly cohesive with few, if any, peds.
sapric peat
Strongly to completely decomposed organic material.
saprolite
Form of decomposed rock characterised by the preservation of
structures that were present in the unweathered rock.
saturated hydraulic
conductivity, K
sat
(Soil Landscape terminology) Hydraulic conductivity is the quantity of
pure water flowing through soil per unit of energy gradient with time. It
may be taken as the percolation rate when infiltration and drainage in a
saturated soil are equal. It is measured as water depth per unit time.
Hydraulic conductivity is an important but often highly variable soil
property. It depends on the management history of the soil.
Estimates are provided as an indication of broad classes of saturated
hydraulic conductivity modified from Craze and Hamilton (1991); and
Hazelton and Murphy (1992). Precision is low. Estimates are made by
field texture, clay fraction and soil structure grade derived from profile
field descriptions (Macdonald et al. 1990; Abraham and Abraham
1992) along with non-dispersed particle size analysis, dispersion,
sodicity and salinity laboratory test results.
Results can be used as input for basic soil water balance models as
well as for coarse hydraulic modelling of catchments.
scald
Two definitions:
a. A flat with no vegetation from which soil has been eroded or
excavated by surface wash or wind, or
b. a bare surface caused by salting. See also saline scald; seepage
scald.
scarp/cliff
Steep slope terminating a plateau or a level upland surface.
schist
A medium to coarse-grained higher-grade regionally metamorphosed
rock exhibiting pronounced foliation due to reorientation of platy
minerals such as micas.
sclerophyll
Denoting the presence of hard stiff leaves, generally indicating an
adaptation to drier conditions.
scoriaceous
A term used to describe a lava or volcanic rock containing cavities
(vesicles) caused originally by bubbles of volcanic gases.
scree
Sheet of any loose, fragmental material, lying on or mantling a slope.
Whilst some consider this to be synonymous with talus, others use this
term more specifically to refer to a generally unconsolidated mantle of
Glossary of Terms used in Soil and Landscape Science
61
loose rocky fragments covering a pre-existing landform, and thereby its
shape and angle is influenced by that underlying landform. See also
talus.
screen
Remnant of country rocks which separates different granitic plutons.
Screens can range from kilometres wide to only a few metres wide.
scroll
Long, curved, very low ridge built up by channelled streamflow and left
relict by channel migration; part of a meander plain.
scrub
Vegetation structure consisting of shrubs 2 – 8 m tall.
seasonal cracking
Refers to those shrinking clay soils which, during a dry period, develop
cracks ≥5 mm wide and which penetrate >0.3 m into the soil material
(Northcote 1979). However, if the surface soil is massive, all such
cracks may not be evident at the surface. As a minimum, the
frequency of cracking should be of the order of one crack per m
2
.
seasonal waterlogging
(Soil Landscape terminology) Seasonally high water tables result in
similar problems to permanently waterlogged soils. Soils in landscapes
with this limitation can become extremely dry for long periods.
sedimentation
Deposition of sediment. The typical use for the term infers deposition
by water. In a soil conservation context, sedimentation is an end-point
in the erosion process with transported soil material being deposited in
locations such as in a channel, along a fence line, on an area of low
slope or a gully, creek, river, sediment trap or dam.
sediments, sedimentary
rocks
Rocks which result from the consolidation of sediment derived from the
wastage of pre-existing rocks and/or from organic accumulations and
chemical precipitates; distinguished from loose sediments by the
degree of lithification.
seepage scalds
Bare areas of soil where rising watertables and the accumulation of
salts and/or sodium at the soil surface have killed vegetation, resulting
in subsequent removal of topsoil by erosion (see salinity and potential
and known discharge areas).
self-mulching
Loose surface mulch of very small peds which form when soil dries
out.
semi-arid
Climate with 250 – 500 mm annual rainfall.
Septic absorption
potential
(Soil Landscape terminology) This assumes site conditions are
favourable and is a ranking of the soil in the base and lower sides of
the absorption trench. Rankings are based on the long-term soil
effluent acceptance rate being 10–20mm/d. Alternative disposal
methods such as spray irrigation may be feasible if septic absorption
potential is very low.
Soils in the sides and base of absorption trenches that have a very low
(VL) potential for septic absorption have one or more of the following
characteristics:
• Exchangeable sodium is >6% or dispersion is >50%. Sodic soils
are rendered impermeable due to high sodium absorption ratios of
Glossary of Terms used in Soil and Landscape Science
62
domestic wastewaters (Patterson 2001). Saturated hydraulic
conductivity of sodic soils can be expected to drop below the long-
term acceptance rate.
• Saturated hydraulic conductivity is <50 mm/d or >1,400 mm/d (AS
1547 2000).
• Limited ability to absorb nutrients, i.e. phosphorus sorption is less
than 125 mg/kg, cation exchange capacity is <6 me/100 g, or
base saturation is >80%.
• Rock volume is >50%. Rocky soils are generally expensive to
excavate (United States Department of Agriculture 1983).
Soil materials that do not have the above properties are rated using
the USCS classification ranking of Finlayson (1982). Where borderline
USCS ratings are given, the first ranking is used.
sesquioxide
Oxides of aluminium and iron.
shale
A fine-grained detrital sedimentary rock which is laminated and easily
split into layers.
shallow soils
(Soil Landscape terminology) Shallow soils are <50 cm deep. Shallow
soils restrict plant growth and increase the difficulty of installing
underground services. Soil depth is measured from the current soil
surface to weathered parent material, or bedrock, or the top of any
hardpan layers that would not be considered as soil for plant growth or
construction.
sharp boundary
Boundary <5 mm wide.
shear strength rating
(Soil Landscape terminology) Shear strength assessments are based
on relative shear strength of USCS groups (Finlayson 1982). Shear
strength is a factor in the assessment of slope instability.
sheet erosion
The removal of the upper layers of soil by raindrop splash and/or
runoff, with no perceptible channels being formed.
sheet erosion risk
(Soil Landscape terminology) The long-term susceptibility of a parcel
of land to sheet erosion if the soil is left exposed and no erosion
control management is employed. The factors that contribute to sheet
erosion risk include rainfall erosivity, soil erodibility and slope gradient.
sheet-flood fan
Level to very gently inclined landform pattern with extremely low relief
and numerous, rapidly migrating, very shallow, incipient stream
channels forming a divergent to unidirectional, integrated or interrupted
reticulated pattern. Aggraded by frequently active sheet flow and
channelled stream flow with subordinate wind erosion. Typical
elements are plain and stream bed. See also alluvial fan; pediment.
shield volcano
Broad, gently sloping surface consisting of overlapping basalt flows.
shrink-swell potential
(Soil Landscape terminology) Expansive soil materials shrink and swell
with changes in moisture content. Such soil materials have volume
expansions >30% or linear shrinkages <17%, and characteristics such
as slickensides, seasonal cracking and high plasticity. When the
moisture content of the soil changes, shrink-swell soils can damage
Glossary of Terms used in Soil and Landscape Science
63
structures such as buildings, roads, dams, walls and underground
services that are not appropriately designed. The shrink-swell potential
of most soils can be reduced by compaction, addition of lime or
gypsum, or burial beneath a stable material. Soil movement can be
eliminated by keeping soil moisture levels constant.
Categories used are:
• Low— linear shrinkage of 0 – 12%
• Moderate— linear shrinkage of 12 – 17%
• High— linear shrinkage of 17 – 22%
• Very high— linear shrinkage of >22%.
shrink-swell soil
A soil which reacts to a change in water content with a change in soil
volume, swelling with increasing moisture content and shrinking as it
dries out.
silcrete
Strongly indurated siliceous material cemented by and largely
composed of forms of silica including quartz, chalcedony, opal and
chert.
siliceous
Having a high proportion of quartz. Usually a descriptor for sands or
silica-rich precipitates.
Siliceous Sand
(Great Soil Groups classification) Deep profile of sands to clayey
sands with no horizon differentiation except for a darker A
1
.
sill
A sheet of horizontal or near horizontal igneous rock intruded into
layers of sedimentary rock. The horizontal extent is always greater
than the thickness.
sillimante
An aluminium silicate mineral indicative of higher grade
metamorphism.
silt
Material within the particle size range of 0.002 – 0.02 mm. Non-plastic
when moist and not deposited by floods. See also alluvium.
siltstone
Fine-grained detrital sedimentary rock composed mainly of silt or clay
respectively; will not easily split into layers.
silty bog soils
Brownish-black organo-mineral surface soils with well-developed
structure becoming paler and less organic with depth. The watertable
is present for at least part of the year.
Silurian period
Geological period 440 – 395 million years ago.
single-grained
The soil occurs as a loose, incoherent mass of individual particles
(e.g., unconsolidated sands).
sink hole/dioline
Steep-sided closed depression, eroded by solution, directed towards
an underground drainage way, or by collapse consequent on such
solution; typical of karst terrain.
skeletal soils
Thin soils which present a barren, inhospitable surface to vegetation.
Glossary of Terms used in Soil and Landscape Science
64
slaking
The partial breakdown of soil aggregates in water due to the swelling
of clay and the expulsion of air from pore spaces.
slate
Fine-grained regionally metamorphosed argillaceous rock which has a
well-developed planar cleavage (slaty cleavage) and splits readily into
thin plates.
slope
An incline, upward or downward, from the horizontal. Its angle is
measured in degrees or as the ratio of the difference in elevation to the
horizontal distance between two points, expressed as a percentage.
slump
A slide where the material in motion is not greatly deformed but has a
backward rotation on a generally horizontal axis, i.e. displacement
along a concave surface of separation.
smooth-ped fabric
Peds are evident. Characteristically >50% of the peds are glossy or
smooth-faced.
snuffy
A term coined by Parbery (1939) to describe the massive, powdery
nature of loamy topsoils of Krasnozems that have undergone severe
structural decline due to over-cultivation.
soapy
Soft malleable greasy feel of deep subsoils from soils formed on
granodiorites.
sodic soils
(Soil Landscape terminology) Sodic soils have an Exchangeable
Sodium Percentage (ESP) >6%. They have low stability when wet, and
they set hard when dry, reducing permeability and available water
capacity and forming surface crusts that restrict plant establishment
and growth. Diagnostically, they typically exhibit high bulk density and
strength, a strong coarse blocky or columnar structure, and are both
highly erodible and dispersible. However, their degree of dispersion in
the field depends on several other factors such as salinity, pH, clay
content, mineralogy and organic matter. Not all sodic soils are
dispersible, nor are all dispersible soils sodic.
sodicity
A measure of exchangeable sodium in the soil. High levels adversely
affect soil stability, plant growth and/or land use.
Sodosol
(Australian Soil Classification Soil Order) Soils with strong texture
contrast between A horizons and sodic B horizons which are not
strongly acid.
softwood plantation
Land where the vegetation has been cleared and replaced with a
plantation of softwood species, e.g., Pinus radiata.
soil
(Soil Landscape terminology) A natural body consisting of layers or
horizons of mineral and/or organic constituents, of variable thickness,
that differs from its parent material in morphological, physical, chemical
and mineralogical properties and biological characteristics (Birkeland
1984).
SoilWorks classification
(Soil Landscape terminology) Soil conservation earthworks are earthen
structures designed and constructed to minimise soil erosion by
Glossary of Terms used in Soil and Landscape Science
65
intercepting and/or diverting run-off. The main earthworks are dams for
water retention, gully control structures for restricting erosion in gullies
and banks for diverting water flow.
The SoilWorks classification is adapted from Table 20.8 of Crouch et
al. (1991). This table forms the basis for determining recommendations
for construction of small farm dams. These dams usually have <5,000
m
3
of water storage capacity and a top water level <3 m above the
original ground surface on the upstream side of the wall. Ratings apply
only for well-graded soils and to situations where the consequence of
failure involves only loss of stored water and no other damage. USCS,
particle size analysis, dispersion and volume expansion results are
used to derive the recommendations. Linear shrinkage test results are
used if available.
A Suitable for normal use. Take care to achieve good
compaction, preferably with moist soil. If the soil is dry (cannot
be moulded), reduce layer thickness to <15 cm. Minimum
batter grades 1:2.5 upstream, 1:2 downstream, except for CH
and MH classifications, when they should be decreased to 1:3
and 1:2.5, respectively.
B Stable and impervious when well-compacted (≥85% of Proctor
maximum dry density). To achieve this, the soil should be close
to the optimum moisture content for the compaction plant, be
placed in layers <15 cm thick and compacted with four
complete passes of a crawler tractor or roller. For crawler
tractors, the soil should be sufficiently moist to be made into a
thread 10 mm thick, but not moist enough to be rolled thinner
than 3 mm without breaking. Minimum batter grades are 1:3
upstream, and 1:2.5 downstream.
C Aggregated material that may not hold water. Compact with at
least four passes of a sheepsfoot roller when the soil is slightly
wetter than the optimum moisture content for compaction
(when it can be rolled into a 3-millimetre diameter thread). Use
a vibrating roller for dry soils. An ameliorant—STPP or sodium
carbonate—is probably required. If the EAT is Class 6 or the
dispersion percentage is less than 6, then the dam is likely to
leak unless it is sealed with better clay or treated with an
ameliorant to induce dispersion.
D Highly susceptible to tunnelling or piping failure. It must be well
compacted throughout to reduce permeability and saturation
settlement. If the soil is drier than is optimum, gypsum or
hydrated lime should be used at 1 tonne per 750 m of wall to
reduce dispersion. The soil should be compacted to at least
85% of Proctor maximum dry density by ensuring the correct
moisture content (see the technique recommended under ‘B:
Suitable for normal use’), placing in layers <15 cm thick and
rolling with at least four complete passes of the plant. For
additional stability, the structure should be designed to hold no
>1 m of water against the wall and batter grades should be
decreased to 1:3.5 upstream and 1.3 downstream.
E Very susceptible to tunnelling or piping failure. In addition to
recommendation D, the structure must hold <1 m depth above
the original ground surface at the upstream side of the wall and
Glossary of Terms used in Soil and Landscape Science
66
not be subject to >0.3 m/d drawdown (trickle pipes must not be
>0.3 m below the top water level). Gypsum or hydrated lime at
1 t/750 m
3
of wall should be incorporated in the upstream side
of the wall. The upstream batter grades should be decreased
to 1:4.
F Very susceptible to tunnelling or piping failure. Due to the high
shrink-swell potential, batter grades must be decreased. In
addition to recommendation D, freeboard must be increased to
>1 m above surcharge level and hydrated lime or gypsum
should be applied at rates determined in the laboratory. Batter
grades should be decreased to 1:4 upstream and 1:3
downstream.
G The high shrink-swell potential of this soil can result in cracks
extending through the wall below the top water level. To reduce
this possibility, a compact central core (≥85% Proctor
maximum compaction) must be obtained by constructing when
the soil is sufficiently moist to be rolled into a 10 millimetres
diameter thread, but not moist enough to roll to 3 mm without
breaking. The freeboard must be increased to >1 m above
surcharge to prevent surface cracks extending below the
waterline. Recommended batter grades are 1:3.5 upstream
and 1:3 downstream. The structure must be designed to retain
sufficient water to keep the wall moist and minimise cracking.
H Not recommended for use, unless all the following precautions
are implemented. The central core must be well compacted,
preferably with a vibrating sheepsfoot roller, to obtain a density
of ≥85% Proctor maximum as determined in the laboratory.
The settled freeboard must be increased to >1 m above
surcharge level, and batter grades should be to at least 1:4
upstream and 1:3 downstream.
I Pervious soil. This soil is not recommended for general use in
soil conservation earthworks, but may be used in a zoned
embankment or sealed with bentonite or a plastic liner.
Recommended batter grades are 1:3 upstream and 1:3
downstream.
J Not recommended for use.
K Usually unsuitable for construction.
When two USCS symbols have been given for borderline
classifications, two differing recommendations may be given. In these
cases, the more conservative recommendation should be used.
soil colour
The colour of soil material as determined by comparison with a
standard Munsell soil colour chart (Munsell ###
soil creep
A generally imperceptible slow downward transportation of soil under
the influence of various erosive agents.
soil depth
The depth of the soil from surface to bedrock.
soil fire hazard
(Soil Landscape terminology) Highly organic soils, such as peats or
litter build-up, can be ignited by vegetation fires during drought. They
Glossary of Terms used in Soil and Landscape Science
67
may smoulder for months and are very difficult to control. Peat fires
lower ground levels, sterilise the soil and in some instances, leave the
ground bare for subsequent erosion.
soil horizon
A layer of soil approximately parallel to the land surface with
morphological properties different from layers below and/or above the
layer. See also A horizon; B horizon; C horizon; D horizon.
Soil Landscape
(Soil Landscape terminology) An area of land with recognisable and
specifiable topography and soils, capable of representation on maps,
and that can be described using concise statements. Landscapes can
be used to distinguish mappable areas of soils because similar causal
factors are involved in the formation of both landscapes and soils.
Similarly, constraints to rural and urban development of land are
related to both landscape and soil qualities. The soil landscape
concept permits the integration of both soil and landform constraints
into a single mapping unit. Each soil landscape is given a name based
on the locality where a typical example occurs and an alphabetic code
(two letters for soil landscapes products, three letters for soil and land
resources products).
Soil Landscape Variant
(Soil landscape terminology) Very like their parent soil landscapes,
usually varying in only a few physical features. They are either not
sufficiently different or of insufficient areal extent to be soil landscapes
in themselves. They are identified by an additional letter after the
parent soil landscape code.
Soil Material
(Soil Landscape terminology) A three-dimensional soil entity which has
a degree of homogeneity and lateral continuity. Each soil material is
defined and described in terms of its readily recognised and
characteristic morphological properties and geographic abundance.
The definitive attributes may vary from one soil material to another,
depending on what is recognisably characteristic of the materials. In
most cases, each soil material has a consistent set of properties and
qualities, because soil materials are not necessarily defined by soil
formation processes or position within a soil profile. Introduced fill,
regolith or unconsolidated alluvium may be included; however, soil
materials usually correspond with soil horizons. Each soil material has
a unique code consisting of the soil landscape code and a unique
number.
soil reaction trend
The change in pH with depth in a soil profile, from surface soil to deep
subsoil. Four such trends have been defined: strongly acid, acid,
neutral and alkaline. (Northcote 1979)
soil structure
Refers to the distinctness, size, shape and condition of natural, or
artificially produced soil aggregates (peds). The degree of structural
distinctness is referred to as grade of pedality. See also single-grained;
massive; weak pedality; moderate pedality; strong pedality.
sola
The upper part of the soil profile, i.e., A and B horizons.
Solodic Soil
See Solodised Solonetz and Solodic Soil.
Glossary of Terms used in Soil and Landscape Science
68
Solodised Solonetz and
Solodic Soil
(Great Soil Groups classification) Soils with strong texture contrast,
well-developed bleached A
2
horizon over an alkaline medium to coarse
angular blocky structure of typically strong consistency.
Solonchak
(Great Soil Groups classification) Soils dominated by salt accumulation
and which show one or more of the following characteristics: salty
encrustations, surface flaking, polygonal cracking of the surface,
powdery structure and lack of normal plant growth except for
salt-tolerant species.
Solonetz Soil
(Great Soil Groups classification) Soils with prominent texture
differentiation between neutral to slightly alkaline, loamy topsoils and
strongly alkaline, clay subsoils.
Solonised Brown Soil
(Great Soil Groups classification) Soils characterised by large amounts
of calcareous material in the profile both in the fine earth fraction and
as soft and hard segregations consisting of calcium and magnesium
carbonates, but usually the calcium is dominant.
Soloth
(Great Soil Groups classification) Acid soils with strong texture contrast
between pale topsoil and clay subsoil with coarse blocky or columnar
structure.
solum
The upper part of a soil profile above the parent material in which
current processes of soil formation are active. This is where the living
roots and other plant and animal life characteristics are exhibited.
species
Group of organisms potentially capable of breeding to produce viable
offspring; taxonomic unit of classification.
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 floodplain.
sporadic occurrence
Relates to a soil or landscape hazard or quality which occurs
occasionally in a random manner across a landscape. It is not related
to soils, underlying geology or a landform element.
stagnant alluvial plain
An alluvial plain where erosion and aggradation by channelled and
overbank streamflow are barely active or inactive because of reduced
water supply, without apparent incision or channel enlargement that
would lower the level of stream action. Typical elements are stream
channel and plain (dominant). Includes bar, scroll, levee, backplain,
swamp, ox-bow, flood-out and lake. See also floodplain; terrace.
Stagnant Alluvial Soil
Landscape
(Soil Landscape terminology) Occur as alluvial plains where erosion
and aggregation by channel and over-bank flow is barely active
because of reduced water flow and stream migration. Typical landform
elements are usually subdued and often inactive. They include plains,
some higher terraces, prior streams, back plains and swamps.
steep slopes
(Soil Landscape terminology) Several landscape hazards increase with
slope. Soil erosion is more severe, rock outcrop is more common, soils
are generally shallower and mass movement is more likely with
Glossary of Terms used in Soil and Landscape Science
69
increasing slope; therefore, slope is an important attribute that can limit
many land uses and an important controlling factor for both urban and
rural capability. Steep slopes are defined as being >33% (18
o
).
stone lags
Residual accumulation of stones from which finer material has been
removed.
stone line
A layer of gravel within a soil profile.
stoniness
(Soil Landscape terminology) Gravels, stones and rocks increase the
cost and difficulty of excavation for underground services and increase
the difficulty of cultivation. Gravels, stones and rocks occupy soil
volume, reducing plant exploitable moisture and nutrients. Surface
stones can have mixed effects on water infiltration, soil erodibility and
moisture loss through evaporation. Soils that contain more than 20 –
50% coarse fragments are stony.
STPP
Sodium tripolyphosphate. A manufactured chemical used for the
dispersion of aggregated soils such as in the sealing of leaking dams.
stream channel
Linear, generally sinuous, open depression, in parts eroded, excavated
and aggraded by channelled streamflow. Includes streambed, banks
and bars.
streambank
Very short but laterally extensive slope, moderately inclined to
precipitous, forming the margin of a stream channel and resulting from
erosion or aggradation by channelled stream flow; part of a stream
channel.
streambank erosion
The removal of soil from a streambank, typically during periods of high
streamflow.
streambed
Linear, generally sinuous, open depression forming the bottom of a
stream channel eroded and locally excavated, aggraded or built up by
channelled streamflow; parts that are built up include bars; part of a
stream channel.
strike
Direction taken by a structural surface such as a fault or bedding plane
as it intersects the horizontal.
strong pedality
The soil contains peds that are clearly observed.
strongly coherent B
horizon
B horizons in which the consistence strength ranges from very firm to
strong throughout, or they contain sub-horizons with these properties.
Included are pan-like materials that have been variously described as
orstein, coffee rock or Sandrock.
structural decline hazard,
structural degradation
hazard6
(Soil Landscape terminology) Through inappropriate management
techniques such as overgrazing and/or excessive cultivation when too
wet or dry, soils may become structurally degraded over time.
Structural decline usually involves at least one of the following:
• increased soil bulk density
• increased strength and cloudiness
• decreased soil organic matter content
Glossary of Terms used in Soil and Landscape Science
70
• decreased soil porosity
• formation of hardpans or hardsetting layers at or near the soil
surface.
Comparisons between the different land uses of sites, most notably
between native or pristine areas and disturbed or developed areas,
can often vividly demonstrate soil structural decline. Management
strategies to overcome structural decline include:
• use of mulches
• appropriate crop and pasture rotation
• minimum or no-tillage practices
• herbicide control of weeds
• more appropriate stocking rates.
structured clays
Soils of uniform texture (i.e. clays) that cannot be classified by the
Great Soil Group (GSG). These soils have moderate to strong
structure, are deep and are generally dark They are associated with
soils such as Black Earths, and Brown and Grey Clays.
structured loams
Generally shallow soils with a distinct pedality, minimal horizon
differentiation and a mainly loamy texture.
Structured Red Earth
Pedal reddish (5 YR Value/Chroma 5) loamy to clay loam soils with
gradual increase in clay content with depth over a gradual to diffuse
boundary.
Structured Yellow Earth
These are soils like Yellow Earths except that the subsoils’ structure
may be pedal rather than earthy. The Structured Yellow Earths are
intergrades between Yellow Earths and Yellow Podzolics.
sub-angular blocky
Like angular blocky except peds are bounded by flat and rounded
faces with limited accommodation to the faces of surrounding peds.
Many vertices are rounded.
subdominant peds
Form when dominant peds either pack together to form large
compound entities or break into smaller units. Subdominant peds are
less conspicuous than dominant peds.
sub-humid
Climate with 500 – 1,500 mm annual rainfall.
subplastic
A soil which appears to become more clayey (i.e., harder to work) with
prolonged kneading. It is usually red, well-structured and well-drained.
subsoil
Subsurface soil material comprising the B horizons of soils with distinct
profiles. In soils with weak profile development, the subsoil can be
defined as the soil below the topsoil.
subspecies
A grouping within a species (i.e. subgroup) used to describe variants of
that species.
sulfidic materials
Subsoil, waterlogged, mineral or organic materials that contain
oxidisable sulfur compounds, usually iron disulfide (e.g., pyrite, FeS
2
)
that has a field pH >4.0 but which will become extremely acid when
drained.
Glossary of Terms used in Soil and Landscape Science
71
sulfuric materials
Soil materials that have a field pH <4.0 when measured in dry season
conditions because of the oxidation of sulfidic materials.
summit surface
Very wide, level to gently inclined crest with abrupt margins, commonly
eroded by water-aided mass movement or sheetwash.
supratidal flat
Large flat subject to infrequent inundation by water that is usually salty
or brackish; aggraded by tides.
surface condition
Describes the actual surface condition of the exposed soil surface.
Options include gravelly; hardsetting; loose; friable; self-mulching;
seasonal cracking; crusting; and recently cultivated.
surface movement
potential
The degree to which the soil rises and falls with changes in moisture.
swale
Linear, level-floored depression excavated by wind, or a relict feature
between ridges built up by wind or waves, or built up to a lesser height
than them; or a long curved relict open or closed depression between
scrolls built up by channelled streamflow.
swamp
Almost level, closed or almost closed depression with a seasonal or
permanent watertable at or above the surface, commonly aggraded by
overbank streamflow and sometimes biological accumulation.
swamp complex
Mixed growth forms: low shrubs, heath, swamp grasses, sedges,
rushes and forbs.
swamp hummock
Steep-sided hummocks rising above a flat swamp surface.
Swamp Soil Landscape
(Soil Landscape terminology) Soil landscapes dominated by ground
surfaces and soils that are at least seasonally wet. Soil parent material
includes large amounts of accumulated decayed organic matter. Water
tables are frequently close to the surface. Landform elements may
include swamps and some relic oxbows, abandoned channels,
lagoons and swales.
swash zone
The area affected by the rush of seawater up beach following the
breaking of waves.
syenite
Coarse-intermediate plutonic igneous rock; the intrusive equivalent of
trachyte; usually contains orthoclase, microdine or perthite, a small
amount of plagioclase, hornblende and other mafic minerals but little or
no quartz.
syncline
Fold in rock strata that is bowed downwards with the youngest rocks in
the centre of the fold.
T
tachylite
Volcanic glass of basaltic composition.
Glossary of Terms used in Soil and Landscape Science
72
tall open-forest
Vegetation structure consisting of trees ≥30 m with a canopy cover
30 – 70%.
tall shrubland
Canopy cover <70% and maximum height >2 m.
talus
Moderately inclined to steeply waning lower slope, aggraded by
gravity, usually formed from an accumulation of rock fragments and
other soil material at the foot of a cliff or steep slope. May be
distinguished from scree in that a talus slope may contain both rocks
and soil and derives its shape from its own characteristics rather than
the underlying landform. See scree.
tenic B horizon
Usually a weakly developed B horizon of texture and/or colour and/or
structure and/or presence of segregations of pedogenic origin
(including carbonate).
Tenosol
(Australian Soil Classification) Soils with generally only weak pedologic
organisation apart from the A horizons.
Terra Rossa Soil
(Great Soil Groups classification) Mainly red soils formed on limestone
or highly calcareous parent materials.
terrace
A former floodplain on which erosion and aggradation by channelled
and overbank streamflow are either barely active or inactive because
deepening or enlargement of the stream channel has lowered the level
of flooding. Typical elements are plain (dominant), scarp and channel
bench. Includes stream channel, scroll and levee.
terracettes
Small terraces on sideslopes resulting from soil creep and/or trampling
by hoofed animals.
Tertiary period
Period of geological time 2 – 65 million years before present.
texture
A measure of the behaviour of a small handful of soil when moistened
and kneaded into a ball and then pressed out between the thumb and
forefinger. It is generally related to the proportion of soil particles of
different sizes (sand, silt, clay and gravel) in a soil, but is also
influenced by organic matter content, clay type and degree of
structural development of the soil.
thalweg
A line connecting the points of deepest flow in successive downstream
channel cross section, i.e., the planform pattern of maximum channel
depth.
thixotrophic
The term applied to soil/liquid systems which are solid when stationary
but which become liquid and mobile when affected by shearing
stresses. Usually refers to thixotrophic clay which is a sodic clay gel
formed when highly sodic clays are saturated.
tidal creek
Intermittently water-filled open depression in parts eroded, excavated
and aggraded by channelled tide water flow; type of stream channel
characterised by a rapid increase in width downstream.
Glossary of Terms used in Soil and Landscape Science
73
tidal flat
Level landform pattern with extremely low relief and slowly migrating
deep alluvial stream channels which form non-directional integrated
tributary patterns. Aggraded by frequently active tides. Typical
elements are plain (dominant) and stream channel. Includes lagoon,
dune, beach ridge and beach.
tillite
Coarse conglomeratic rocks with angular fragments. They are
consolidated from the till deposited from a melting glacier.
tilth
A general term used to describe the physical condition of a soil as
related to its ease of tillage and fitness as a seedbed. A soil in good
tilth will not impede seedling emergence and root penetration.
timber/scrub/unused
forest land
Unlogged state and private forests and partially cleared land which are
not grazed or areas being allowed to regenerate. Does not include
land which is currently being used for agricultural, pastoral or forestry
production.
tonalite
A quartz-diorite igneous rock intermediate in quartz content between a
diorite and a granodiorite.
topography
The shape of the ground surface as depicted by the presence of hills,
mountains or plains. Steep topography is characterised by steep
slopes and hilly land. Flat topography is characterised by flat land with
minor undulations and gentle slopes.
toposequence
Repetitive sequence of soils encountered between hillcrests and the
valley floor. A catena is a special case of a toposequence in which the
parent material is uniform.
topsoil
Part of the soil profile, typically the A
1
horizon, containing material
which is usually darker, more fertile and better structured than the
underlying layers.
tor
Steep to precipitous hillock, typically convex, with a surface mainly of
bare rock, either coherent or comprising subangular to rounded large
boulders (exhumed core-stones, also themselves called tors)
separated by open fissures; eroded by sheet wash or water-aided
mass movement.
torbanite
A type of coal usually formed from algal and fungal matter.
toscanite
Igneous rock composed of phenocrysts of quartz, orthoclase,
plagioclase and often biotite in a grey groundmass.
trachyandesite
A volcanic rock intermediate in character between a trachyte and an
andesite.
trachyte
Fine-grained porphrytic intermediate extrusive rock; main components
are alkali feldspar and minor mafic minerals.
transferral
Deep deposits of mostly eroded parent materials washed from areas
directly upslope.
Glossary of Terms used in Soil and Landscape Science
74
Transferral Soil
Landscape
(Soil Landscape terminology) Soil landscapes formed on deep
deposits of mostly eroded parent materials washed from areas
upslope. Stream channels are often discontinuous and slopes are
generally concave. Transferral landscapes include footslopes, valley
flats, fans, bajadas and piedmonts.
transgressive dune
General term to cover various types of sand deposit moved in the
direction of the effective wind over surfaces other than mobile sand.
transportational site
An area where both sub-surface in situ processes and surface
processes of lateral movement occur.
Transitional Alpine Humus
Soil
Soils characterised by accumulation of humified organic matter
incorporated into mineral soil to form dark topsoil over coloured clay
loam.
travertine
Calcareous material precipitated from groundwater at a hot spring after
passage through calcareous rocks or sediments, sometimes aided by
biochemical activity.
trenching rating
(Soil Landscape terminology) In situ soils that are sufficiently cohesive
(at least when dry) do not generally require shoring supports when
excavated for vertical faces or trenches to depths <1.5 m. The ratings
are per Finlayson (1982). Note: SM classification is mostly good but
can require shoring in some cases. G1 indicates an SM soil.
Triassic period
Period of geological time 180 – 230 million years before present.
trondhjemite
An intermediate intrusive rock like granodiorite but lacking in
potassium feldspar.
tuff
Consolidated volcanic ash; water-laid tuffs generally show excellent
bedding and may appear like shales or sandstones; pyroclastic
fragments are <20 mm in diameter.
tunnel erosion
The removal of subsoil by water while the surface soil remains
relatively intact.
turbidites
Fine-grained graded sediment deposited in deep oceanic
environments.
Type Profile
(Soil Landscape terminology) Typical sequences of soil materials that
occur over significant portions of a soil landscape. Type profiles are
usually the most common arrangement of soil materials within any
landform element.
U
understorey
A layer of vegetation below the main canopy
Glossary of Terms used in Soil and Landscape Science
75
Unified Soil Classification
System, USCS
Based on the identification of soil materials by their particle size,
system grading, plasticity index and liquid (U.S.C.S) limit. These
properties have been correlated with the engineering behaviour of soil
including soil compressibility and shear strength (Casagrande, A.
1947). The system is used to determine the suitability of soil materials
for use in earthworks, optimal conditions for their construction, special
precautions which may be needed, such as soil ameliorants and final
batter grades to be used to ensure stability. USCS classifications
include:
• GW— well-graded gravels, gravel-sand mixtures, little or no fines
• GP— poorly graded gravels, gravel-sand mixtures, little or no
fines
• GM— silty gravels, poorly graded gravel-sand-silt mixtures
• GC— clayey gravels, poorly graded gravel-sand-clay mixtures
• SW— well-graded sands, gravelly sands, little or no fines
• SP— poorly graded sands, gravelly sands, little or no fines
• SM— silty sands, poorly graded sand-silt mixtures
• SC— clayey sands, poorly graded sand-clay mixtures
• ML— inorganic silts and very fne sands, rock four, silty or clayey
fne sands with slight plasticity
• CL— inorganic clays of low to medium plasticity, gravelly clays,
sandy clays, silty clays, lean clays
• OL— organic silts and organic silt-clays of low plasticity
• MH— inorganic silts, micaceous or diatomaceous fne sandy or
silty soils, elastic silts
• CH— inorganic clays of high plasticity, fat clays
• OH— organic clays of medium to high plasticity
• Pt— peat and other highly organic soils.
Borderline soils are marked by dual symbol sets separated by a dash,
e.g. ML-CL. The most dominant class is given first.
Uniform soil
A soil in which there is little, if any, change in soil texture between the
A and B horizons, e.g., loam over loam, or sandy clay over silty clay
(Northcote 1979). See also Duplex soil, Gradational soil, Principal
Profile Form.
unripe
Generally wet to saturated muds and alluvium with no soil
development.
untreated roads rating
Untreated roads and tracks are made from surface soils that are
compacted by traffic. Site consideration such as slope, wetness,
rockiness and soil depth are not included. Trafficability and to a lesser
extent stoniness and dustiness are considered. Ratings are based on
those of Finlayson (1982).
upper storey
The layer of vegetation which is the main canopy layer; top stratum
(usually trees).
urban capability
(Soil Landscape terminology) The ability of a parcel of land to support
a certain intensity of urban development without serious erosion and
sedimentation occurring during construction as well as possible
instability and drainage problems in the long-term (Houghton and
Charman 1986). Urban capability is ranked based on the severity of
Glossary of Terms used in Soil and Landscape Science
76
the limitations that are likely to affect urban land uses (Hannam and
Hicks 1980). These are low, moderate and high (to severe).
• Low (minor) limitations— indicate areas with little or no physical
limitations. Standard building designs may be used.
• Moderate limitations— may influence design and impose certain
management requirements on developments to ensure a stable
land surface is maintained during and after development. These
limitations can be overcome by careful design and adoption of site
management techniques that ensure land surface stability.
• High (to severe) limitations— indicate areas with limitations that
are difficult to overcome, requiring detailed site investigation and
engineering design. Some areas may be so unsuitable for urban
development that they are best left undisturbed.
Capability statements for soil landscapes are intended for regional
planning purposes only. Any capability statements are general and
apply to standard designs. Exceptions to capability statements may
arise both for small pockets of land or soil, or the use of non-standard
designs. Non-standard designs that consider site and soil constraints
may give sustainable solutions.
Although the information given may be of sufficient accuracy and detail
for the planning of small scale, low value, low impact developments,
detailed planning at the local level and more intensive capability
assessments dependent on additional information are often necessary.
Additional site-specific factors such as slope angle, position on slope,
terrain element and specific soil conditions need to be examined and,
where necessary, geotechnical engineering reports obtained. General
capability rankings for applicable types of urban development are
given for each soil landscape.
Urban Capability
Classification
A method of land classification which ranks land by the physical
constraints applying to various intensities of urban land use. Or a
method of land classification which ranks land by its ability to sustain
various intensities of urban land use.
urban land
Land associated with cities or towns. Includes residential, commercial
and recreational areas and their associated infrastructure. Allotment
sizes are generally <1 ha.
V
valley flat
Small, gently inclined to level flat, aggraded or sometimes eroded by
channelled or overbank stream flow, enclosed by hillslopes; a
miniature alluvial plain located on a narrow valley floor.
varved shales
Shales deposited from melted ice in a lake in which the depositional
layers appear in pairs. Each pair represents a seasonal deposit.
vertic properties
Soil material with a clayey field texture and ≥35% clay which cracks
strongly when dry and has slickensides and/or lenticular peds.
Glossary of Terms used in Soil and Landscape Science
77
Vertosol
(Australian Soil Classification) Clay soils with shrink-swell properties
that exhibit strong cracking when dry and at depth have slickensides
and/or lenticular structural aggregates. Although many soils exhibit
gilgai microrelief, this feature is not used in their definition.
vesicular
A term describing volcanic rocks with small spherical or ellipsoid
cavities caused by bubbles of volcanic gas.
Vestigial Soil Landscape
(Soil Landscape terminology) Soil landscapes dominated by sites
where shallow soils have formed from in situ weathering of typically
resistant parent materials. Landform elements can include summit
surfaces, plateaux and old ground surfaces. Rock outcrop may be
common.
volcanic rocks
Igneous rocks, generally originating as lavas (i.e. basalt), which have
cooled and solidified on the earth’s surface.
volcaniclastics
An indurated pyroclastic rock formed from breccia and other fragments
explosively ejected from a volcano.
volcano
Typically, very high and very steep landform pattern, without stream
channels, or with erosional stream channels forming a centrifugal
interrupted tributary pattern. Built up by volcanism, and modified by
erosional agents. Typical elements are cone and crater. Includes
scarp, hillcrest, hillslope, stream bed, lake and maar.
volume expansion, VE
A volume expansion test measures the free swelling of a disturbed soil
sample (sieved <0.425mm) on wetting from air dry to saturation. The
method is described in Wickham and Tregenza (1973); Crouch et al.
(1991); and Craze et al. (1993). Volume expansion rankings are
modified from Crouch et al. (1991).
Soils that shrink, fail to saturate or have volume expansions of <3 are
usually dispersible and associated with phreatic line tunnel failure in
earth dams, especially those that are built with dry soil or are strongly
compacted.
Dispersion often masks the extent of volume expansion in soils
(Mills et al. 1980). For dispersible soils, the linear shrinkage test is also
recommended to indicate the likelihood of shrink-swell behaviour.
When the dispersion percentage is >50%, linear shrinkage testing is
recommended.
voluntary native pasture
Cleared land or woodland with a ground cover of grasses and/or
legumes which are either native species or naturalised (self-sown)
exotic species. Generally lower productivity and nutrient status than
improved pastures.
W
water gap
A narrow gorge cut by a stream through a ridge of hard rock.
Glossary of Terms used in Soil and Landscape Science
78
water repellence
(Soil Landscape terminology) Water repellence is rated after Roberts
and Carbon (1971) by the amount of time needed for a droplet of water
to be absorbed by a dry soil surface. The effects of water repellence
include reduced water infiltration, and poor germination and growth
(Handreck & Black 1984) as well as increased run-off and increased
erosion.
Five degrees of water repellence are recognised:
• <1 second— not significant
• 1 – 10 seconds— very low
• 10 – 50 seconds— low
• 50 – 260 seconds— moderate
• >260 seconds— very high.
Soils that display moderate to very high levels of water repellence are
generally acid, sandy soils with high organic matter. They are often
poor growth mediums for plants due to slow or uneven wetting patterns
and have high rates of run-off.
Methodology for the water repellence test is consistent with that of
Roberts and Carbon (1971). The original three-category system
proposed by these authors has been modified by Craze et al. (1993) to
the five-class system described.
water-repellent soils
Soils which resist wetting when dry. Drops of water do not spread
spontaneously over their surface and into pores. The degree of water
repellence may be severe where water drops remain on a flattened
surface for some minutes. In other cases, drops appear to be
absorbed readily but quantitative measurements show the height of
capillary rise is diminished. This characteristic is mainly a feature of
some sandy soils (topsoils) and is generally attributed to organic
coatings on the sand grains which resist water entry into the soil.
waterlogging
(Soil Landscape terminology) Waterlogged soils have permanent
watertables at or near the surface. They may also be non-cohesive,
organic, saline, acidic, infertile and have low wet-bearing strength.
They are unsuitable for septic effluent disposal. See also permanently
high watertables, seasonal waterlogging.
watertable
The upper surface of unconfined groundwater below which the pores
of rock or soil are saturated. A perched water table is the surface of a
local zone of saturation held above the main body of groundwater by
an impermeable layer, usually clay, and separated from it by the
unsaturated zone.
wave erosion hazard
(Soil Landscape terminology) The removal of sand or soil from the
margins of beaches, beach ridges, dunes, lakes or dams by wave
action. Areas such as beaches and foredunes are subject to severe
storm wave erosion. They should not be developed.
weak pedality
The soil contains peds that are barely observable.
weathering
The physical and chemical disintegration, alteration and decomposition
of rocks and minerals, at or near the earth’s surface, by atmospheric
and biological agents.
Glossary of Terms used in Soil and Landscape Science
79
wet bearing strength, low
(Soil Landscape terminology) Soils with low wet bearing strength are
dominated by a limited range of particle sizes. They are pliable and
deform easily under pressure when wet; ‘quicksand’ is an example. If
poorly drained, they can be unsuitable for foundations and have poor
trafficability when wet. Soils with low wet bearing strength often suffer
severe structural damage if cultivated or become mechanically
disturbed when they are wet.
Low wet bearing strength is rated by the strength of the soil when soil
moisture content is greater than at field capacity (Pons and Zonneveld
1965), and indicates ‘fluid or very soft mud.
wet sclerophyll
Canopy cover 30 – 70% and maximum height >10 m made up of
sclerophyllous trees with at least one moist stratum of mesophytic
shrubs and the frequent presence of ferns.
wetland
Areas of swamp, shallow water or waterlogged land. The water cover
may be permanent or temporary. The areas are usually characterised
by vegetation of a moist-soil or aquatic type.
Wiesenboden
(Great Soil Groups classification) Dark clay to clay loam soils with
uniform to gradational texture profiles and varying development of gley
features in the deeper subsoil due to intermittent partial saturation
associated with seasonal seepage and perched water. Perched water
is a saturated layer of soil which is separated from any underlying
saturated layers by an unsaturated layer.
wilting point
Point at which the rate of moisture loss from the leaf surface is greater
than the uptake from plant roots. The wilting point differs in various soil
types by texture.
wind erosion risk
(Soil Landscape terminology) Typically, areas subject to wind erosion
are exposed and have easily transported, unconsolidated, loose and
fine sand-size aggregates. They are often dry topsoils. Vegetative
cover should be maintained to prevent wind erosion.
woodland
Vegetation structure dominated by trees with canopy cover of 10 –
30%.
worming, wormy
Visible condition of vertically exposed soil caused by through-flow
transporting erodible fine fraction to the surface often characteristic of
high silt content.
X
Xanthozem
(Great Soil Groups classification) Mainly yellow, friable, strongly-
structured clay soils with moderate horizon differentiation and
gradational texture profiles.
xenocryst
Crystals in igneous rock which are foreign to the body of rock in which
they occur.
Glossary of Terms used in Soil and Landscape Science
80
xenolith
Rock fragments from a different type of rock that are imbedded in a
granitic rock.
Y
Yellow Earth
(Great Soil Groups classification) Yellow equivalent of Red Earth.
Yellow Podzolic Soil
(Great Soil Groups classification) Strongly differentiated duplex soils
with light to medium textured A
1
horizon over a pale A
2
over a
yellowish; firm to friable B horizon with generally polyhedral structure.
Glossary of Terms used in Soil and Landscape Science
81
Rankings for Physical Laboratory Test Results
in Soil Landscape Descriptions
Test
Units
Ranking
Very low
Low
Moderate
High
Very high
Clay, Cl
%
≤10
>10 – 25
>25 – 40
>40 – 50
>50
Silt, Si
%
≤10
>10 – 25
>25 – 40
>40 – 50
>50
Fine Sand, FS
%
≤10
>10 – 25
>25 – 40
>40 – 50
>50
Coarse Sand, CS
%
≤10
>10 – 25
>25 – 40
>40 – 50
>50
Gravel, Gr
%
≤4
>4 – 17
>17 – 31
>31 – 65
>65
Dispersion Percentage,
DP
%
0 – 6
>6 – 30
>30 – 50
>50 – 65
>65
Volume Expansion, VE
%
3 – 10
>10 – 20
>20 – 30
>30 – 40
>40
Linear Shrinkage, LS
%
≤7
>7 – 12
>12 – 17
>17 – 22
>22
Water Erodibility (USLE
K)
t.ha.h/
ha.MJ.mm
≤0.01
>0.01 –
0.02
>0.02 –
0.04
>0.04 –
0.06
>0.06
Wind Erodibility
%
≥50
>40 – 50
>25 – 40
>10 – 25
0 – 10
Field Capacity, FC
%
≤10
>10 – 22
>22 – 33
>33 – 44
>44
Permanent Wilting Point,
PWP
%
≤5
>5 – 13
>13 – 22
>22 – 30
>30
Plant Available
Waterholding Capacity,
PAWC
%
≤5
>5 – 10
>10 – 15
>15 – 20
>20
Plasticity, Plas.
USCS
Non-
plastic
CL-ML,
ML-CL,
M, SM,
CL, OL
CL-CH
CH-CL,
OH-CL,
OH-CH,
CH, MH
Saturated Hydraulic
Conductivity, K
sat
mm/d
>12-240
>240 –
481
>481 –
1,440
>1,441 –
2,880
>2,880
Septic Absorption
Potential
USCS
CH, CL,
GC, OH,
SC
OL, SM
GM, MH,
ML, Pt
GW, SP,
SW
Glossary of Terms used in Soil and Landscape Science
82
Building Foundation
Stability
USCS
OH, Pt,
MH
OL, CH
CL
SC
SW, GP,
GW,
CW, GM
Shear Strength
USCS
OL, OH,
Pt
ML, MH
CH, SC,
SM, SP
CL
GW, SW
Road Subgrade
USCS
CH, OH,
Pt
OL, MH
SP, SM,
SC, ML,
CL
GC, SW
GW, GP,
GM
Untreated Roads
USCS
SP, ML,
OK, MH,
CH, OH,
Pt
SM, CL
GW, GM,
SW
SC
GC
Trenching Capability
USCS
G
(Good, no
shoring)
S
(Shoring
required)
Rankings for Chemical Laboratory Test Results
in Soil Landscape Descriptions
Test
Units
Ranking
Very low
Low
Moderate
High
Very high
Acidity (soil:water)
pH
<4.5
(extreme)
<4.5 –
5.0
(very
strong)
<5.1 – 5.5
(strong)
5.6 – 6.0
(medium)
6.1 – 6.5
(slight)
Acidity (soil:CaCl
2
)
pH
<3.7
(extreme)
3.7 – 4.2
(very
strong)
4.3 – 4.7
(strong)
4.8 – 5.2
(medium)
5.3 – 5.7
(slight)
Alkalinity (soil:water)
pH
>9.0
(very
strong)
8.5 – 9.0
(strong)
7.9 – 8.4
(medium)
7.4 – 7.8
(slight)
6.6 – 7.3
(neutral)
Alkalinity (soil:CaCl
2
)
pH
>8.2
(very
strong)
7.7 – 8.2
(strong)
7.1 – 7.6
(medium)
6.6 – 7.0
(slight)
5.8 – 6.5
(neutral)
Buffering Capacity
kmol(H+)
(ha 10 cm)
-
1
(pH)
-1
<20
20 – <30
30 – <75
75 –
<110
≥110
Organic Matter, OM
%
0.5 – 1.0
>1.0 –
2.0
>2.0 – 3.0
>3.0 –
5.0
>5.0
Bray Phosphorus
mg/kg
≤5
>5 – 10
>10 – 20
>20 – 25
>25
Glossary of Terms used in Soil and Landscape Science
83
Lactate Phosphorus
mg/kg
≤5
>5 – 10
>10 – 17
>17 – 25
>25
Phosphorus Sorption
mg/kg
≤125
>125 –
250
>250 –
400
>400 –
600
>600
Salinity (ECe)
dS/m
0 – 2
>2 – 4
>4 – 8
>8 – 16
>16
Rankings for Exchangeable Cation Test
Results in Soil Landscape Descriptions
Test
Units
Ranking
Very low
Low
Moderate
High
Very
high
Cation Exchange
Capacity
me/100
g
≤6
>6 – 12
>12 – 25
>25 – 40
>40
Sum of Bases
me/100
g
≤3
>3 – 7
>7 – 15
>15 – 25
>25
Base Status
-
≤5
(Dystrophic)
>5 – 15
(Mesotrophic)
>15
(Eutrophic)
Base Saturation
%
≤20
>20 – 40
>40 – 60
>60 – 80
>80
Exchangeable Ca
me/100
g
≤2
>2 – 5
>5 – 10
>10 – 20
>20
Exchangeable Ca/CEC
%
≤10
>10 – 30
>30 – 65
>65 – 85
Exchangeable Mg
me/100
g
≤0.3
>0.3 – 1
>1 – 3
>3 – 8
>8
Exchangeable Mg/CEC
%
≤3
>3 – 5
>5 – 10
>10 – 15
>15
Exchangeable K
me/100
g
≤0.2
>0.2 – 0.3
>0.3 – 0.7
>0.7 – 2
>2
Exchangeable K/CEC
%
≤1
1 – 2
2 – 5
5 – 8
>8
Exchangeable Na
me/100
g
≤0.1
>0.1 – 0.3
>0.3 – 0.7
>0.7 – 2
>2
Exchangeable Na/CEC
%
≤6
(Non-sodic)
>6 – 15
(Sodic)
>15 – 25
(Strongly
sodic)
>25
(Very
strongly
sodic)
Exchangeable Al/CEC
%
≤5
>5 – 10
>10 – 15
>15 – 35
>35
Glossary of Terms used in Soil and Landscape Science
84
Ca/Mg Ratio
<1
(Ca
deficient)
>1 – 4
(Ca low)
>4 – 6
(Balanced)
>6 – 10
(Mg low)
>10
(Mg
deficient)
Mg/K Ratio
<1
(Mg
deficient)
>1 – 2.5
(Mg low)
>2.5 – 5
(Balanced)
>5 – 10
>10
(K
deficient)
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