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Site IS17

Location: Horsham

Morphological Soil Type: Horsham Clay

Australian Soil Classification: Endohypersodic, Epipedal, Grey VERTOSOL

Northcote Factual Key: Ug 5.24
Great Soil Group: grey clay
Mapping Unit: Horsham Clay.


General Landscape Description: Level area in the flood plain (prior stream).
Site Description: The site was cleared and cultivated and occurs five kilometres east of Horsham in the original 'Youngs' and 'Riverside' Irrigation areas.
Geology: Late Tertiary to Quaternary Shepparton Formation.
Native Vegetation: Original vegetation may have been dominated by a Grey Box (Eucalyptus microcarpa) savanna woodland.

Image: IS17  Landscape
IS17 Landscape


Soil Profile Morphology:

Surface Soil

A10-10 cmDark grey (10YR4/1); light clay; subplastic; cracking and slightly self-mulching surface condition; moderate subangular blocky structure; strong consistence dry, slightly sticky consistence wet; contains very few (< 2 %) soft carbonates; pH 7.3; sharp and smooth change to:

Image: IS17 Profile
IS17 Profile
Subsoil

B2110-55 cmDark grey (10YR4/1); light clay; subplastic; moderate very coarse prismatic structure; strong consistence dry, moderately sticky consistence wet; pH 7.6; gradual change to:

B2255-115 cmGrey (2.5Y5/1); medium clay; plastic; weak subangular blocky structure; strong consistence dry, moderately sticky consistence wet; pH 7.6; gradual change to:

B23115-180 cmLight grey (2.5Y7/2); medium clay; plastic; weak subangular blocky structure; strong consistence dry, moderately sticky consistence wet; pH 8.5.

Key Profile Features:
  • High clay content throughout soil profile.
  • Vertic properties (ie. significant shrink-swell characteristic).

Soil Profile Characteristics:

pH
Salinity Rating
Surface
(A1 horizon)
Slightly Alkaline
Low
Non-Sodic
None
Subsoil
(B21 horizon)
Slightly Alkaline
High
Sodic
None1
Deeper Subsoil
(at 1 m)
Slightly Alkaline
Very High
Strongly Sodic
None1
1 Due to high levels of soluble salts.

Image: IS17_Graphs

The profile is slightly alkaline throughout.The salinity rating is low in the surface. The subsoil is high becoming very high with depth.The surface is non-sodic. The upper subsoil is sodic becoming strongly sodic with depth.The clay content is high throughout the profile.


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
0–10
7.3
NA
0.19
0.04
13.2
8.4
1.9
0.9
NA
5.2
31.4
16.6
10
26
14
50
B21
10–55
7.6
NA
1.11
0.2
12.1
13.9
1.6
4.2
NA
4.9
NA
25.1
5
14
15
64
B22
55–115
7.6
NA
3.06
0.7
11.4
17.4
1.7
6.4
NA
3
NA
28.1
3
10
14
71
B23
115–180
8.5
NA
1.72
0.39
10.3
16.1
1.8
8.2
NA
1.8
NA
32.1
4
15
10
67
Note: NA=not assessed.

Management Considerations:

Whole Profile
  • Plant available water capacity (PAWC) is considered to be low (estimated at 55 mm). This is based on available laboratory data and assumes an effective rooting depth of 30 cm. Effective rooting depth will be restricted by the high level of soluble salts in the subsoil.
Surface (A) Horizon
  • When the soil is dry, heavy rains will move down soil cracks. This rapid recharge can be valuable for the survival of plants near wilting. When wet, the soil will swell and further infiltration of water will be relatively slow.
  • Tillage of cracking clay soils should be avoided if the soil is wet (ie. wetter than the plastic limit). At such a moisture condition, excessive tillage, trafficking or overstocking can result in structural degradation (eg. compaction, smearing) occurring. Ideally, tillage should take place on clay soils such as these when the soil is drier than the plastic limit, down to at least the tillage depth.
Subsoil (B) Horizons
  • The level of soluble salts is high in the upper subsoil and becomes very high from 55 cm depth. These levels of soluble salts are likely to significantly restrict the growth of a number of plant 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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