TREES AND SHRUBS FOR THE MIDLANDS AND NORTHERN WHEATBELT 2 nd Edition 134
In describing the districts of the Midlands and Northern Wheatbelt, 32 generalised terms have been
used to describe the various types of soil. Definitions of each of these terms are given below.
These soil descriptions record the changes in colour and texture of the various layers or horizons
form the surface down the soil profile to a depth of 1 or 2 m. The main terms used to describe the
different textures are sand, loam, clay and gravel, and various combinations of these. For example:
Colour and Texture
very light grey sand
In this example, the 0-30 cm layer would be referred to as the topsoil and the clay below 30 cm as the
subsoil. Also indicated is the presence of hardpans, shallow rock and saline watertables where these
are typical features of a particular soil type.
Soil descriptions such as these enable comparisons to be made between one site and another and
are a help in the selection of plant species for sites being revegetated.
Brown sands over red-brown clay Brown sands and sandy loams overlying red-brown clays which may be mottled and
may contain carbonate concretions at about 90 cm.
Crabholes (gilgai) Gilgai soils (commonly called crabholes) are characterised by a surface of small hollows
and hummocks occurring usually on level or very gently sloping plains. The surface
features are caused by the swelling and shrinking of clays in the subsoil.
Deep, grey sand This soil is usually a neutral deep, pale grey sand, with darkening due to organic matter
at the surface. Sometimes the sand grades into a pale yellow at depth. These soils are
of low fertility and water holding capacity, and plant establishment may be difficult.
TREES AND SHRUBS FOR THE MIDLANDS AND NORTHERN WHEATBELT 2 nd Edition 135
Deep, pale yellow sand Very similar in texture to the soil profile
Deep, yellow sand, but the soil colour is
noticeably paler throughout the profile. Some of these may have a grey surface. The
pale yellow sands are of inherently lower fertility than the yellow sands. Plant
establishment on them will be more difficult.
Deep, yellow sand This soil type commonly consists of up to 2 m of yellow sand with a slight increase in
clay content with depth. That is, the texture often increases from sand at the surface to
a clayey sand and sometimes a sandy clay loam by 2 m depth. The soil is neutral or
slightly acidic in reaction throughout the profile. The pH values in water are about 6.
Deep, yellow sand, acid.
Deep, yellow sand, acid This soil is very similar in colour and texture to
Deep, yellow sand, but it is acidic to
strongly acidic in reaction. The pH values in water are often well below 5.
Deep, red-brown sand These are friable earthy sands ranging in colour from yellow-brown to red-brown.
Deep, red sand This soil is red sand throughout the profile and is usually over 1 m in depth.
Gravel at the surface, massive laterite exposed Small rounded nodules of ironstone gravel or laterite make up the surface of this soil,
with massive cemented sheets of laterite also showing. This soil is a very shallow
version of the
Sand over gravel soil, with the surface sand layer absent. They are
likely to be very harsh sites for revegetation.
TREES AND SHRUBS FOR THE MIDLANDS AND NORTHERN WHEATBELT 2 nd Edition 136
Grey sand over clay or hardpan, usually seasonally wet The soils are usually a deep, grey sand over a mottled clay or a siliceous or organic
hardpan. These soils are saturated each winter. A gravel layer may be present.
Laterite; lateritic sandplain The term laterite refers to the small rounded nodules of ironstone commonly called
gravel. Where these nodules are cemented together to form a continuous sheet it is
referred to as massive laterite. Sandplain overlying this material is often referred to as
Limey sands These are deep, white to very light grey sand composed of very finely ground shell
fragments that are alkaline in reaction.
Red and brown alkaline clays These clay soils, variously red and brown and sometimes gritty at the surface, are
alkaline to very alkaline in reaction.
Red gradational The word gradational means that the soil texture gradually increases in clay content
from the topsoil down through the subsoil. Red gradational soils are red colour
throughout and change in texture from sand or loamy sand at the surface through sandy
loam and sandy clay loam to clay at depth.
Red gradational over hardpan As for
Red gradational soil, but with a cemented hardpan layer present.
Red gradational, saline As for
Red gradational soil, but affected by the presence of shallow saline
TREES AND SHRUBS FOR THE MIDLANDS AND NORTHERN WHEATBELT 2 nd Edition 137
Red sandy loam over clay Typically this soil is a red sandy loam over red clay at about 15-30 cm depth.
Red sandy loam over hardpan The soil profile is similar to the
Red sandy loam over clay soil described above, but
the upper part of the subsoil has a discontinuous, pale cemented layer (hardpan) that is
sometimes exposed at the surface as a consequence of sheet erosion.
Rocky terrain This description refers to areas dominated by outcropping rocks with very little soil
development between the boulders.
Sand over gravel Typically this soil is 15-30 cm, or up to 100 cm, of grey to pale yellow sand over
ironstone gravel. The gravel is often small, rounded nodules and can comprise up to 90
per cent of the soil mass. The gravel is sometimes cemented into hard sheets. Below
the gravel layer a yellow mottled clay layer is usually present. Areas of these soils are
called 'lateritic sandplains' and they are very common throughout the region.
Sand over gravel - saline As for
Sand over gravel soils, but affected by the presence of shallow, saline
Sand over red or yellow clay This is usually grey sand over yellow or yellow mottled clay, or red sand over red clay at
about 30 cm depth.
Sand over red or yellow clay - saline As for
Sand over red or yellow clay but affected by shallow saline groundwater.
TREES AND SHRUBS FOR THE MIDLANDS AND NORTHERN WHEATBELT 2 nd Edition 138
Sandy loam The one area of this soil sampled was in the Greenough district, on the landscape unit
referred to as 'Black flats' and was a brown to red-brown, fine sandy loam throughout
Shallow limey sand over calcrete hardpan or limestone This soil has up to 30 cm of fine, grey calcareous sand over a calcrete hardpan, or
occasionally limestone. Shelly layers may occur in the profile.
Shallow sand over clay This soil is commonly a sand, often only centimetres deep over a clay. These soils are
at risk of becoming saline as groundwater levels rise.
Shallow soil over chert or basalt Chert, sandstone or basalt occurs just beneath the soil surface with outcropping rock.
Shallow soils vary from yellow brown loamy sand for chert or sandstone to red brown
sandy loam to red brown clay loam for basalt associated with the Billeranga ranges.
Shallow soil over granite or gneiss As the name indicates, granite or gneiss rock occurs just beneath the soil surface and
frequently outcrops. The shallow soil varies in texture from coarse gritty sand to sandy
loam and the colour ranges from dark grey to red-brown.
Shallow soil over sandstone As for
Shallow soil over granite or gneiss , but the underlying rock is sandstone. The
shallow soil is usually pale yellow or red, coarse sand.
Silty clays These soils are usually dark brown in colour, a silty clay loam at the surface merging to
heavy clay at depth. They are variably neutral to alkaline at the surface and have
TREES AND SHRUBS FOR THE MIDLANDS AND NORTHERN WHEATBELT 2 nd Edition 139
Yellow loamy sand Similar to the
Deep, yellow sand but with slightly heavier texture.
Yellow or yellow/brown sand over limestone This soil comprises a very variable depth of yellow or brown sand over limestone - depths range
from very shallow (10 cm) to several metres. Rock outcrops may occur.
INDEX: COMMON NAMES TREES AND SHRUBS FOR THE MIDLANDS AND NORTHERN WHEATBELT 2 nd Edition 140