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NE31

Group: Tallangatta Valley Landcare GroupAustralian Soil Classification: Acidic, Dystrophic, Red DERMOSOL
Northcote Factual Key: GnGreat Soil Group: red podzolic
General Landscape Description: Midslope of a low hill (slope 12%) on Ordovician sediments.
Site Description:

Photo:  NE31 Landscape
NE31 landscape


Soil Profile Morphology:

Surface Soil

O

0-2 cm

Organic mat:

Photo:  NE31 Profile
NE31 profile
A1
2-12 cm
Dark brown (7.5YR3/4); fine sandy clay loam; firm consistence dry; contains many (25%) colluvial gravel (6 mm average diameter); pH 4.8; clear change to:
Subsoil

B1

12-25 cm

Yellowish red (5YR5/8); clay loam (fine sandy); moderate medium blocky structure; pH 5.0; clear change to:

B21

25-40 cm

Red (2.5YR5/8); light clay (fine sandy); moderate medium blocky, breaking down to weak fine blocky structure; pH 4.9.

B/C
40-70 cm
Dark red (2.5YR4/8); light fine sandy clay loam ; moderate medium blocky, breaking down to weak fine blocky structure; pH 5.5:

C
70+ cm
Base rock. Depth to bedrock varies across the pit from 25 cm to 1 metre depth.

Note:
This horizon is a mix of soil (10%) and rock (90%).



Key Profile Features:
  • Lack of clear texture change between surface (A) and subsoil (B21) horizon.
  • Shallow soil profile.

Soil Profile Characteristics:
Horizon
pH
Salinity Rating
Surface
(A1 horizon)
very strongly acid
very low
non-sodic
none
Subsoil
(B21 horizon)
strongly acid
very low
non-sodic
none
Deeper subsoil
(at 60 cm)
moderately acid
very low
non-sodic
none

Photo:  NE31 Graphs

Horizon
Horizon Depth
(cm)
pH
(water)
pH
(CaCl2)
EC 1:5
Exchangeable Cations
Ca
Mg
K
Na
meq/100g
A1
2-12
4.8
4.1
<0.05
2.3
0.3
0.2
<0.1
B21
12-25
5.0
4.2
<0.05
0.7
0.2
0.1
<0.1
B22
25-40
4.9
4.2
<0.05
1
0.3
0.3
<0.1
B/C
40-70
5.5
4.7
<0.05
7.2
1.5
0.2
<0.1

Horizon
Horizon Depth
(cm)
Exchangeable Aluminium
mg/kg
Field Capacity
pF 2.5
Wilting Point
pF 4.2
Coarse Sand
(0.2-2.0 mm)
Fine Sand
(0.02-0.2 mm)
Silt
(0.002-0.02 mm)
Clay
(<0.002 mm)
A1
2-12
210
30.6
11.6
14
30
23
26
B21
12-25
220
28.2
10.9
10
33
23
33
B22
25-40
260
23.7
14.5
10
25
18
48
B/C
40-70
30
33.7
12.4
12
38
23
18

Management Considerations:

Whole Profile
  • Plant available water capacity (PAWC) is considered to be low (estimated at 60 mm) for this site. This is based on available laboratory data and assumes an effective rooting depth of 70 cm. Rooting depth will be restricted by the baserock.
  • The soil profile will be relatively well drained. Subsoil drainage will be good as water will easily penetrate the fractured and well weathered fine-textured bedrock.

Surface (A) Horizon
  • In the strongly acid surface horizon, the level of exchangeable aluminium measured in the laboratory (210 mg/kg) is high enough to restrict the growth of a range of aluminium sensitive species (eg. lucerne, phalaris, some clovers, tall fescue). A pH/aluminium test on a bulked sample taken across the paddock will give a better guide as to how much lime is needed to raise pH. Increasing soil pH will assist in reducing the level of aluminium toxicity. Other factors, however, need to be considered before lime is recommended (eg. pasture species grown, method of application, local trial responses, soil surface structure and likely cost/benefit).
  • The surface soil has a low inherent nutrient status (based on the sum of the exchangeable basic cations). Organic carbon and total nitrogen levels are relatively high. Organic matter is important on surface soils such as these (with high fine sand and silt contents) for maintaining surface soil stability. Low levels of organic matter will promote slaking and subsequent aggregate breakdown, leading to exacerbated surface sealing and hardsetting.

Subsoil (B) Horizons
  • Levels of exchangeable aluminium remain high in the upper subsoil. Surface lime application will have negligible benefit to subsoil acidity.
  • Inherent fertility is very low in the upper subsoil horizons (based on the exchangeable basic cations).

Notes
Profile described by Mark Imhof, Paul Rampant and Karen De Plater (25/10/95).
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