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Site IS14

Location: Murtoa

Morphological Soil Type: Drung Sandy Clay Loam

Australian Soil Classification: Calcic, Subnatric, Red SODOSOL

Northcote Factual Key: Dr 2.33
Great Soil Group: red-brown earth
Mapping Unit: Drung Sandy Clay Loam


General Landscape Description: Crest of a slight rise in the prior stream flood plain landscape.
Site Description: Cleared and cultivated area, six kilometres south west of Murtoa.
Geology: Late Tertiary to Quaternary Shepparton Formation.
Native Vegetation: Probably originally Buloke (Casuarina luehmannii) vegetation.

Image: IS14 Landscape
IS14 Landscape


Soil Profile Morphology:

Surface soil

A10-5 cmDark brown (7.5YR3/4); fine sandy clay loam; plastic; hardsetting surface condition; weak coarse angular blocky structure; strong consistence dry, moderately sticky consistence wet; pH 7.8; sharp and wavy change to:

Image: IS14 Profile
IS14 Profile


A25-10 cmBrown (7.5YR4/3) sporadically bleached (10YR7/1); fine sandy clay loam; weak coarse blocky structure; pH 8.1; sharp and wavy change to:

Subsoil

B2110-25 cmReddish brown (5YR4/4); light clay; plastic; moderate coarse prismatic structure; strong consistence dry, moderately sticky consistence wet; pH 8.7; sharp and wavy change to:

B2225-45 cmYellowish red (5YR4/6); light clay; plastic; moderate coarse prismatic structure; strong consistence dry, moderately sticky consistence wet; pH 9.3; clear and wavy change to:

B231k45-90 cmStrong brown (7.5YR5/6) with faint yellowish red (5YR4/6) fine mottles; medium clay; plastic; weak blocky structure; strong consistence dry, moderately sticky consistence wet; contains very few (< 2 %) hard carbonates and a few (2-10%) soft carbonates; pH 9.3:

B232k90-130+ cmStrong brown (7.5YR5/6) with faint yellowish red (5YR4/6) fine mottles; medium clay; plastic; weak blocky structure; strong consistence dry, moderately sticky consistence wet; contains very few (< 2 %) hard carbonates and a few (2-10%) soft carbonates; pH 9.3.

Key Profile Features:

  • Strong texture contrast between surface (A) horizons (< 24% clay) and subsoil (B21) horizon (56% clay).

Soil Profile Characteristics:


pH

Salinity Rating
Surface
(A1 horizon)
Slightly Alkaline
Low
Non-Sodic
None1
Subsoil
(B21 horizon)
Strongly Alkaline
Low
Sodic
Slight
Deeper Subsoil
(at 1 m)
Very Strongly Alkaline
High
Very Strongly Sodic
None2
1 Moderate dispersion after remoulding. 2 Due to high levels of soluble salts.

Image: IS14 Graphs

The surface soil is slightly alkaline. The upper subsoil is strongly alkaline becoming very strongly alkaline with depth.The salinity rating is low in the surface and upper subsoil becoming high with depth.The surface is non-sodic. The upper subsoil is sodic becoming very strongly sodic with depth.The clay content jumps markedly at the surface subsoil boundary.


Horizon
Sample Depth cm
pH
EC
dS/m
Sodium Chloride
%
Exchangeable Calcium
cmol-/kg
Exchangeable
Magnesium
cmol-/kg
Exchangeable Potassium
cmol-/kg
Exchangeable Sodium
cmol-/kg
Exchangeable Aluminium
mg/kg
Exchangeable Acidity
cmol-/kg
Field
Capacity
-30okPa
Permanent
Wilting
Point
-1500okPa
Coarse
Sand
%
Fine
Sand
%
Silt
%
Clay
%
H2O
CaCl2
A1
0–5
7.8
NA
0.11
0.01
7
3.8
0.7
0.6
NA
2.7
19.6
8.4
20
45
8
24
A2
5–10
8.1
NA
0.07
0.01
4.7
3.4
0.4
0.9
NA
2
NA
6.7
22
48
9
20
B21
10–25
8.7
NA
0.18
0.03
10
12.5
1.6
3.9
NA
1.3
NA
23.3
12
24
5
56
B22
25–45
9.3
NA
0.48
0.06
9.4
17.1
1.6
6.8
NA
NA
NA
26.7
6
17
4
69
B31k
45–90
9.3
NA
1.03
0.13
6
13.3
1.5
8
NA
NA
NA
23.3
9
20
5
55
B32k
90–130
9.3
NA
1.17
0.18
5.2
12.6
1.4
7.8
NA
NA
NA
20.1
13
22
7
47
B233
130–190
9.2
NA
1.11
0.16
NA
NA
NA
NA
NA
NA
NA
20.3
12
22
9
53
B234
190–230
8.6
NA
1.05
0.17
NA
NA
NA
NA
NA
NA
NA
21.1
11
26
7
54
Note: NA=not assessed.

Management Considerations:

Whole Profile
  • Plant available water capacity (PAWC) is considered to be relatively low (estimated at 79 mm). This is based on available laboratory data and assumes an effective rooting depth of 45 cm. Effective rooting depth will be restricted by the strongly sodic deeper subsoil which has a high level of soluble salts.

Surface (A) Horizons
  • The surface soil disperses moderately after remoulding. This indicates that cultivation or overstocking of the soil when in a wet condition may result in dispersion and consequent structural degradation (eg. exacerbated hardsetting, surface sealing, cloddiness) occurring.
  • The surface soil has a high fine sand content (ie. 45%) and is hardsetting when dry. Soils such as these rely to a large extent on organic matter for maintaining aggregation. Organic matter will build up under pasture but will decline if cultivation takes place. Practices such as residue retention, minimum tillage and including pasture rotations could be utilised if cropping takes place in order to build up organic matter.
  • The subsurface (A2) horizon is sodic and is likely to disperse significantly after remoulding. This indicates that if tillage occurs when this horizon is in a wet condition, a plough pan may develop. Gypsum application on such soils may assist in improving soil structural condition.

Subsoil (B) Horizons
  • The coarsely structured subsoil becomes strongly sodic from 25 cm depth, and has a low exchangeable calcium to magnesium ratio (ie. < 0.6). This is likely to result in restricted root and water movement in the subsoil. The presence of a conspicuous bleach in the A2 horizon indicates that water movement into the subsoil is being restricted.
  • The high level of exchangeable sodium and magnesium in the subsoil may also result in nutrient imbalances and may even have a toxic effect on some plants.
  • The strongly alkaline subsoil indicates that some nutrients (eg. manganese, iron, copper, zinc) may be poorly available to plants.
  • The level of soluble salts becomes high from 45 cm depth. This is likely to restrict the growth of salt sensitive species (eg. faba beans, chickpeas, lupins).

Profile Described By: John Martin, Nabil Badawy, Ron Cawood, Geoff Pope, John Galea, John Turner (1970).

Reference: "Major Agricultural Soils of the Wimmera Irrigation Area". John Martin, Mark Imhof, Lourey Ruth, Rob Nink, Karen DePlater, Paul Rampant, Sonia Thompson, S. Alexander. Department of Natural Resources and Environment, Victoria. 1996.
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