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LS13a


Location: Netherby

Australian Soil Classification: Epicalcareous-Epihypersodic, Self-mulching, Grey VERTOSOL

Northcote Factual Key: Ug 5.2
Great Soil Group: grey clay

General Landscape Description: Low lying area of gently undulating plain.
Site Description: Undisturbed roadside reserve.
Native Vegetation: Black Box (Eucalyptus largiflorens) and Lignum Bush (Muehlenbeckia cunninghamii) is the natural vegetation.



Image: LS13a Landscape
LS13A Landscape
Image: LS13a Landscape 2
LS13A Landscape another perspective.


Soil Profile Morphology:

Surface Soil

A10-10 cmDark yellowish brown (10YR3/3); medium clay; self-mulching; strong fine blocky structure; strong consistence dry; pH 8.4; clear change to:

Image: LS13a Profile
LS13A Profile
Subsoil

B2110-30 cmDark yellowish brown (10YR4/2); heavy clay; weak coarse prismatic, parting to strong medium blocky structure; very strong consistence dry; contains a few (2-5%) soft carbonate segregations; pH 9.0; clear and wavy change to:

B2230+ cmStrong brown (7.5YR4/6); medium heavy clay; strong medium subangular blocky structure; strong consistence dry; contains a common (> 20%) amount of soft carbonate; pH 9.2.

Key Profile Features:
  • Clay texture throughout profile.
  • Self-mulching surface soil.
  • Occurrence of significant cracking in the soil profile when dry. Cracking often appears at soil surface.

Soil Profile Characteristics:

-

pH


Salinity
Surface
(A1 horizon)
Moderately Alkaline
Low
Non-Sodic
Slaking, No dispersion1
Subsoil
(B21 horizon)
Strongly Alkaline
Low
Strongly Sodic
None2
Deeper Subsoil
(at 50 cm)
Strongly Alkaline
High
Strongly Sodic
Strong
1 Slight dispersion after remoulding. 2 Strong dispersion after remoulding.

Image: LS13a Graphs
The surface soil is moderately alkaline. The subsoil is strongly alkaline throughout.The salinity rating is low in the surface and upper subsoil becoming high with depth.The surface is non-sodic. The subsoil is strongly sodic.


Chemical and Physical Analysis:

Horizon
Horizon Depth
(cm)
pH
(water)
pH
(CaCl2)
EC
dS/m
Sodium Chloride
%
Exchangeable Cations
Ca
Mg
K
Na
meq/100g
A1
0-10
8.4
7.7
0.19
18.5
6
1.4
0.7
B21
10-30
9
7.9
0.3
<0.05
10.5
8.4
0.9
4.4
B22
30-60
9.2
8.7
1.12
0.2
6.7
12
1.1
8.2

Horizon
Horizon Depth
(cm)
Total
Nitrogen
%
Oxidisable Organic Carbon
%
Field
Capacity
pF2.5
Wilting
Point
pF4.2
A1
0-10
0.15
1.7
26.2
17.5
B21
10-30
31.7
22.6
B22
30-60

Management Considerations:

Surface (A) Horizon
  • The surface soil is self-mulching which provides a good seed bed that is friable and easily worked. The surface becomes sticky when wet.
  • The surface soil has a high inherent fertility (based on the sum of the exchangeable basic cations).
  • Tillage or excessive trafficking should be avoided if the soil is wetter than the plastic limit. Such disturbance may result in soil structural degradation (eg. compaction, smearing) occurring. Ideally, tillage should take place when the soil is drier than the plastic limit down to at least the depth of tillage.

Subsoil (B) Horizons
  • The top of the subsoil is strongly sodic but does not disperse (unless mechanically disturbed when moist). It is also strongly alkaline which indicates that certain nutrients may be poorly available to plants (eg. zinc, iron, copper and manganese).
  • From 30 cm depth the subsoil is strongly sodic and strongly dispersive which will result in root and water movement being restricted. The level of soluble salts increases in this horizon which will restrict the growth of salt sensitive plants. Few roots were observable below 30 cm depth at the pit face.

Profile Described By: Mark Imhof, John Martin, David Rees, Sonia Thompson (May 1994).
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