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GP55

Location: KernotAust. Soil Class.: Acidic, Eutrophic, Grey DERMOSOL
General Landscape Description: Crest of rolling hill on a dissected peneplain.
Geology: Cretaceous sediments.

GP55 landscape
GP55 Landscape


Soil Profile Morphology:

Surface Soil

A110-15 cmVery dark greyish brown (10YR3/2); very fine sandy clay loam; massive structure; firm consistence dry; pH 5.1; clear change to
GP55 profile
GP55 Profile
A1215-35 cmDark brown (10YR3/3) with few (8%) brownish yellow (10YR6/8) mottles; very fine sandy clay loam; weak to moderate coarse polyhedral structure; very firm consistence dry; pH 5.1; gradual change to
Subsoil
B135-50 cmDark greyish brown (10YR4/2) with dark yellowish brown (10YR4/6) mottles; conspicuously bleached in patches fine sandy clay loam; moderate coarse prismatic, parting to moderate coarse blocky structure; very firm consistence dry; pH 5.2; clear and wavy change to
B2150-70 cmDark greyish brown (10YR4/2) with common (15%) brownish yellow (10YR6/8) mottles; light medium clay; strong coarse prismatic, parting to moderate blocky structure; pH 5.4; gradual and wavy change to
B2270-100 cmGreyish brown (10YR5/2) with many (25%) brownish yellow (10YR6/8) mottles; light medium clay; strong coarse prismatic, parting to moderate blocky structure; very firm consistence dry; pH 5.4
C100+ cmCretaceous mudstone

Key Profile Features:

  • Lack of strong texture contrast between surface (A) horizons of subsoil (B21) horizons.
Soil Profile Characteristics:

pH
Salinity Rating
Surface
(A1 horizon)
Strongly Acid
Very Low
Non-Sodic
-
Subsoil
(B21 horizon)
Strongly Acid
Very Low
Sodic
None1
Deeper Subsoil
(at 1 m)
Strongly Acid
Very Low
Sodic
None2
1 strong dispersion after remoulding
2 complete dispersion after remoulding

GP55 pH
The whole profile is strongly acid
throughout.
GP55 Exchangeable aluminium
The exchangeable aluminium levels
in the surface horizon are very high
and become extremely high from
15 cm depth to 1 metre.
GP55 Sodicity
The surface soil is non-sodic.
The subsoil is sodic.
GP55 clay
The clay content increases gradually
with depth.

Horizon
Horizon Depth
pH (water)
pH CaCl2
EC
1:5
NaCl
Exchangeable Cations
Ca
Mg
K
Na
Meq/100g
A11
0-15
5.1
4.2
0.08
3.9
2.7
0.56
0.55
A12
15-35
5.1
4
0.07
2.3
2.5
0.32
0.59
B1
35-50
5.2
4
0.07
1.3
4
0.31
0.94
B21
50-70
5.4
4
0.07
1.3
6.2
0.47
1.6
B22
70-100
5.4
4.1
0.11
2.6
13
0.63
3.6

Horizon
Horizon Depth
Ex Al
mg/kg
Ex Ac
meq/100g
Wilting Point
pF4.2
g/100g
Coarse Sand
(0.2-2.0mm)
%
Fine Sand
(0.02-0.2mm)
%
Silt
(0.002-0.02mm)
%
Clay
(<0.002mm)
%
A11
0-15
150
19
12.5
4
24
45
21
A12
15-35
320
18
11.2
1
24
46
25
B1
35-50
270
15
14.2
1
22
43
31
B21
50-70
280
17
17
1
20
40
37
B22
70-100
280
16
24.4
1
16
36
44


Management Considerations:

Whole Profile

  • Much of the soil profile is strongly acid. As a result, deficiencies in molybdenum, potassium and phosphorus may occur. Manganese toxicity may also occur in strongly acid soils, particularly when poorly drained (as waterlogging may bring manganese into solution). Levels of exchangeable aluminium measured are very high throughout the profile (i.e. ranging from 150 to 320 mg/kg within the surface (A) horizons). This is likely to restrict the growth of aluminium sensitive species. A pH/aluminium test sampled across the paddock would be most appropriate to determine how much lime is needed to raise soil pH. However, other factors need to be considered before lime is recommended (e.g. pasture species grown, method of application, local trial responses, soil surface structure and likely cost/benefit).
Surface (A) Horizons
  • The inherent fertility of the surface (A1) horizon (based on the sum of the exchangeable calcium, magnesium and potassium cations) is low. The high levels of organic matter at this site are important for improving soil fertility, water holding capacity and enhancing surface soil structure.
Subsoil (B) Horizons
  • The dense and coarsely structured upper subsoil (B21) horizon is sodic and has a low exchangeable calcium to magnesium ratio (0.2). However, strong dispersion only occurs after remoulding. The high levels of exchangeable aluminium (280 mg/kg) in the subsoil may be the cause of the restricted dispersion. The subsoil is dense and coarsely structured which will restrict root movement down the profile.
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