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GP58

Location: Richardson HillAust. Soil Class.: Vertic, Mottled-Subnatric, Brown SODOSOL
General Landscape Description: Lower midslope of down hill (10% slope).Geology: Tertiary basalt.


GP 57 to 60 Landscape
GP57-GP60 Landscape


Soil Profile Morphology:

Surface Soil

A110-15 cmVery dark greyish brown (10YR3/2); fine sandy clay loam; moderate medium polyhedral, parting to fine structure; very firm consistence dry; pH 5.6; gradual change to:GP58 profile
GP58 Profile
A1215-25 cmDark brown (10YR3/3); clay loam; moderate medium polyhedral, parting to strong fine polyhedral structure; firm consistence dry; pH 6.2; abrupt change to:
Subsoil
B2125-80 cmDark brown (10YR3/3) with faint brownish yellow (10YR6/6) mottles; heavy clay; moderate very coarse polyhedral, parting to strong coarse polyhedral, blocky structure; slickensides with highly polished clay skins evident; strong consistence moist; pH 6.6; gradual change to:
B2280+ cmDark greyish brown (10YR4/2) with red (2.5YR5/8) mottles; heavy clay; slickensides evident; strong consistence moist; pH 5.3.

Key Profile Features:

  • Vertic properties present within the subsoil i.e. slickensides.
Soil Profile Characteristics:

pH
Salinity Rating
Surface
(A1 horizon)
Moderately Acid
Low
Non-Sodic
Slight
Subsoil
(B21 horizon)
Sightly Acid
Very Low
Marginally Sodic
None
Deeper subsoil
(at 80 cm)
Strongly Acid
Very Low
Sodic
None
1slight dispersion after remoulding

GP57 pH
The surface horizon is moderately acid.
The upper subsoil is slightly acid becoming
strongly acid at 80 cm depth.
GP57 salinity
The salinity rating in the surface horizon
is low becoming very low in the subsoil.
GP57 Exchangeable Aluminium
The exchangeable aluminium levels
in the surface horizons are negligible
becoming very high at 80 cm depth.
GP57 clay
The clay content increases abruptly
at the A/B boundary.

Horizon
Horizon Depth
pH (water)
pH CaCl2
EC
1:5
NaCl
Exchangeable Cations
Ca
Mg
K
Na
Meq/100g
A11
0-15
5.6
4.9
0.13
6.5
3.1
0.74
0.56
A12
15-25
6.2
5.1
0.05
5.5
4.1
0.19
0.61
B21
25-80
6.6
5.5
0.07
6.3
10
0.26
1.6
B22
80+
5.3
4.4
0.18
4.3
12
0.24
3.2

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
<10
10
18.4
8
26
32
25
A12
15-25
<10
8.8
14.1
5
29
32
29
B21
25-80
<10
9.9
27
2
13
14
67
B22
80+
230
14
27.8
2
15
17
64

Management Considerations:

Surface (A) Horizons

  • The inherent fertility of the surface (A1) horizon (based on the sum of the exchangeable calcium, magnesium and potassium cations) is moderate. The high levels of organic matter at this site are important for improving soil fertility, water holding capacity and enhancing surface soil structure. The nitrogen levels are also high. Planting legumes may help to alleviate the low fertility deficiency.
  • The surface (A1) horizon is non-sodic but disperses slightly. This indicates that tillage or over-stocking of the soil whilst in a moist to wet condition may result in structural degradation (e.g. surface sealing, increased cloddiness) occurring. Raindrop action on bare soil may have a similar effect, so it is important to maintain surface cover. Gypsum application may assist in improving surface soil structural condition on such soils.
Subsoil (B) Horizons
  • The subsoil has a moderate inherent fertility throughout (based on the sum of the exchangeable basic cations).
  • The presence of mottling throughout the subsoil indicates that the profile is seasonally waterlogged.
  • The subsoil has vertic properties i.e. slickensides which indicates that significant shrinking and swelling occurs during wetting-drying cycles. This can disrupt the roots of perennial plants and will have implications for engineering applications (e.g. building foundations and fence lines).
  • The dense and coarsely structured upper subsoil (B21) horizon is sodic and has a low exchangeable calcium to magnesium ratio (0.7). However, no dispersion occurs which is beneficial to root growth. Interestingly, roots were observed to 60 cm depth.
  • At 80 cm depth the soil becomes strongly acid and the exchangeable aluminium levels very high at 230 mg/kg. Only deep rooted plants would be effected.
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