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GP62

Location: Cowwarr.Australian Soil Classification: Melanic, Eutrophic, Black DERMOSOL.
Geology: Holocene fluvial deposits.General Landscape Description: Level plain (0-1% slope).
Mapping Unit: Thomson.Site Description: Dairy grazing paddock.

Photo: Site G62 Landscape
Site GP62 Landscape

Soil Profile Morphology:

Surface Soil

A11 0-25 cm Very dark greyish brown (10YR3/2); fine sandy loam; strong medium polyhedral, parting to fine polyhedral structure; weak consistence dry; pH 5.7; gradual change to:

Photo: Site G62 Profile
Site GP62 Profile
A12 25-40 cm Very dark greyish brown (10YR3/2); fine sandy clay loam; strong medium polyhedral, parting to fine polyhedral structure; firm consistence dry; pH 6.4; gradual change to:

Subsoil

B2140-60 cmVery dark brown (10YR2/2); light clay; weak coarse prismatic, parting to strong medium to fine polyhedral structure; very firm consistence dry; pH 5.9; gradual change to:

B2260-100 cmDark brown (10YR3/3) (with a bleached appearance on some ped faces); light clay (silty); moderate coarse prismatic, parting to strong medium polyhedral structure; strong consistence dry; pH 5.8; gradual change to:

B23100-120 cmDark greyish brown (10YR4/2) with brown (7.5YR4/4) mottles and a bleached appearance on some ped faces; light clay silty; moderate coarse prismatic, parting to strong coarse polyhedral structure; strong consistence dry; manganese stains common; pH 6.6.

Key Profile Features:
  • Gradual increases in clay content with depth.
  • Well structured surface and upper subsoil.
Soil Profile Characteristics:

Horizon
pH
Salinity Rating
Surface
(A1 horizon)
Moderately Acid
Moderate
Non-sodic
None
Subsoil
(B21 horizon)
Moderately Acid
Very Low
Non-sodic
None
Deeper subsoil
(at 1 m)
Slightly Acid
Very Low
Non-sodic
None


Graph: pH levels in Site G62





The surface and upper subsoil is
moderately acid. The deeper
subsoil becomes slightly acid.
Graph: Sodicity levels in Site G62



The profile is non-sodic throughout.
Graph: Salinity levels in Site G62



The surface salinity rating is moderate.
The subsoil salinity rating is very low
throughout.
Graph: Clay% in Site G62



The clay content increases gradually
with depth.

Horizon
Horizon Depth

(cm)

pH

(water)

pH

(CaCl2)

EC 1:5
NaCl
Exchangeable Cations
Ca
Mg
K
Na
meq/100g
A11
0-25
5.7
5.1
0.22
10
2.9
0.24
0.29
A12
25-40
6.4
5.6
0.09
8.3
4.4
0.14
0.29
B21
40-60
5.9
4.9
0.09
5.7
6.1
0.14
0.44
B22
60-100
5.8
4.8
0.08
4.1
6.1
0.13
0.42
B23
100-120
6.6
5.5
0.1

Horizon
Horizon Depth
(cm)
Exchangeable Aluminium
mg/kg

Exchangeable Acidity

meq/100g
Field Capacity
pF2.5
Wilting Point
pF4.2
Coarse Sand
(0.2-2.0 mm)
Fine Sand
(0.02-0.2 mm)
Silt
(0.002-0.02 mm)
Clay
(<0.002 mm)
A11
0-25
<10
11
10.9
2
52
19
18
A12
25-40
-28
8.7
12.2
2
41
25
25
B21
40-60
<10
11
16.3
2
17
36
39
B22
60-100
<10
3.4
15.4
2
18
38
38
B23
100-120

Management Considerations:

Whole Profile
  • Plant Available Water Capacity (PAWC) is considered to be moderate-high (estimated at 130 mm) for this soil profile. This is based on an estimated effective rooting depth of 60 cm (ie. surface soil and upper subsoil). The denser and more coarsely structured deeper subsoil is likely to restrict rooting depth, although not as significantly as some of the more sodic subsoils in the region. PAWC has been estimated using a model developed by Littleboy (1995) which uses analytical data for clay %, silt %, fine sand %, coarse sand % and wilting point.
  • Infiltration of water will be rapid throughout the upper soil profile due to the well developed structure and pore space available.
Surface (A) Horizons
  • The level of soluble salts in the surface is moderate and may restrict the growth of salt sensitive species. These levels may be unnaturally high due to the effects of the dry season at the time of sampling (1996/97) and are likely to decline following heavy rainfall and/or irrigation.
  • The relatively deep surface soil is well structured (parting to many fine polyhedral shaped peds) and is friable when moist. Soil consistence when moist is also weak for this horizon. As a result of these attributes the surface soil will provide excellent seed-bed conditions, creating few limitations to root and water movement.
  • The surface (A1) horizon has a moderate nutrient holding capacity (based on the sum of the exchangeable calcium, magnesium and potassium cations).
  • The surface soil has a very high fine sand content (ie. 50%). Soils such as these rely on organic matter to maintain soil structure. Maintaining organic matter levels will also assist in improving soil fertility and water holding capacity.
  • Infiltration of water into the well structured surface soil will be quite high and this horizon will be well drained.
Subsoil (B) Horizons
  • The upper subsoil is well structured (parting to many fine polyhedral shaped peds). Root and water movement is not likely to be significantly restricted as a result.
  • The deeper subsoil (from 60 cm depth) becomes more coarsely structured and will be more restrictive to root movement.
Profile Described By: Mark Imhof, David Rees and Ian Sargeant (21/04/1998).
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