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SFS5

SFS5 landscape
Soil pit at SFS5 showing extremely variable horizon thicknesses associated with gilgai

    Site Code
SFS5


SFS5 profile

Left: Hypernatric, Grey SODOSOL
Right: Vertic, Mottled-Subnatric, Brown SODOSOL
    Location
Brewster, Trawalla East Road (West of Ballarat)
    Landform
Undulating plain
    Geology
Quaternary volcanic, basalt.
    Element
Simple slope
    Slope
2–5%
    Aspect
North
Horizon
Depth (cm)
Description (‘hollow’ of gilgai) = left half of profile image
Ap
0–20 Brown (10YR4/3 moist) to pale brown (10YR6/3 dry), fine sandy loam to loam, weak to very firm consistence (depending on colour – lighter = stronger); Highly variable and mixed material. Ap originally likely to be less than 10 cm and is now dominated by apedal, A2 material. pH 5.5; clear boundary to:

A2
20–20/90 Light brownish grey(10YR6/2 moist) to white (10YR8/2 dry); fine sandy loam or gravelly loam; pockets of medium to very coarse (5–30 mm) buckshot gravel comprises up to 80% of this horizon in places and can form a layer 100–400 mm thick (at some sites this is cemented into a pisolitic mass), <10% is magnetic; pH 6.1; clear, irregular boundary to:

B21gt
20/90+ Mottled dark grey (10YR4/1 moist) (50%) and yellowish brown (10YR5/6 moist), with fine dark red (2.5YR4/8) mottles becoming weak red (2.5YR5/4) at depth; medium clay; fine (<5 mm) smooth-faced polyhedral structure; pH 7.0.

Horizon
Depth (cm)
Description (‘hollow’ of gilgai) = left half of profile image
Ap
0–20 AS FOR HOLLOW (above)

B21tg
20–70 Mottled light olive brown (2.5Y5/4) and olive yellow (2.5Y6/6); medium clay; irregular medium to coarse (40–80 mm) prismatic parting to medium to coarse (15–40 mm) angular blocky or polyhedral structure; roots between peds contrasts with lack of roots at this depth in the ‘hollow’ component of the gilgai; clear boundary to:

B22gss
70+ Olive brown (2.5Y4/4 moist) with many (20-50%) light olive brown (10YR5/6) mottles; medium heavy clay; frequent small slickensides; less well developed structure than B21.

Management considerations
Described by the owner as ‘crabhole country’, this slightly elevated, gently sloping land has well developed ‘gilgai’ features in the subsoil. The very variable nature of this soil is evident in material in the beds which have white A2 horizon material, buckshot, pisolitic cemented buckshot and subsoil clay all present at the ground surface. ‘Spew’ or ‘hollow units’ are elongated downslope (~10 m). ‘Puffs’ are of smaller lateral dimensions than the ‘hollows’ being 1–3 metres across. In the excavated pit, two faces were picked back. SFS5a to show deep A2 with buckshot and SFS5b to show puff unit (shallow depth to clay).

This soil presents real problems to the agriculturalist. Water holding properties are extremely different in the ‘puff’ compared with the hollow and this is often evident in the crop. The topsoil is not well structured, disintegrates to a ‘flour’ when dry-tilled, is weak and ‘spewy’ when wet and hard set when dry. Protection of the surface with ground cover is essential to reduce the slaking and sealing effects of rain. Under high rainfall / runoff conditions this soil is potentially highly erodible. The subsoil is sodic and has a high clay content so this soil is also prone to severe waterlogging. The slope of the land and the forming of beds should alleviate this in the surface horizons but erosion is a potential hazard should the furrows carry excessive runoff.

Analytical data
Site SFS5a 'Hollow'
Sample
depth
pH
EC
NaCl
Ex Ca
Ex Mg
Ex K
Ex Na
Ex Al
Ex acidity
FC
(-10kPa)
PWP
(-150kPa)
KS
FS
Z
C
Horizon
cm
H2O
CaCl2
dS/m
%
cmolc/kg
cmolc/kg
cmolc/kg
cmolc/kg
mg/kg
cmolc/kg
%
%
%
%
%
%
Ap
0–10
5.5
5.1
0.31
0.02
4.1
0.8
0.6
<0.1
<10
1.0
33.0
9.1
4.1
37.7
27.5
20
A2
30–50
6.1
5.4
0.07
N/R
0.86
0.57
0.15
0.19
<10
1.4
22.0
3.1
2.2
48.8
37.5
10.5
B21gt
80ญญ–100
7.0
6.0
0.21
N/R
5.8
12.0
0.66
3.9
N/R
11
53.6
30.8
1.0
8.0
5.5
80.5

Site SFS5a 'Puff'
Sample
depth
pH
EC
NaCl
Ex Ca
Ex Mg
Ex K
Ex Na
Ex Al
Ex acidity
FC
(-10kPa)
PWP
(-150kPa)
KS
FS
Z
C
Horizon
cm
H2O
CaCl2
dS/m
%
cmolc/kg
cmolc/kg
cmolc/kg
cmolc/kg
mg/kg
cmolc/kg
%
%
%
%
%
%
Ap
0–20
5.5
5.1
0.31
0.02
4.1
0.8
0.6
<0.1
<10
1.0
33.0
9.1
4.1
37.7
27.5
20.0
B21tg
25–50
6.5
5.7
0.21
N/R
6.7
12.0
1.5
1.6
N/R
11.0
51.2
28.7
0.8
10.1
7.5
78.0
B22gss
80ญญ–100
7.5
6.6
0.30
0.03
5.1
9.7
0.7
2.4
N/R
N/R
55.3
31.1
1.1
6.2
4.5
80.0


SFS5 image
Raised beds formed in the paddock at Brewster.
Note the slight undulations in the line of the beds and the pockets of paler (A2)
material that have been brought to the surface.

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