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LP86

Group: Raywood Farm Advance GroupAustralian Soil Classification: Hypocalcic, Mesonatric, Red SODOSOL
Northcote Factual Key:Dr 2.13 Great Soil Group: red-brown earth
General Landscape Description: Old alluvial plain. Original vegetation included Yellow Box (Eucalyptus melliodora), Grey box (E. microcarpa) and Buloke (Casuarina luehmannii).

LP86 Landscape
LP86 Landscape


Soil Profile Morphology

Surface Soil

A10-6 cmStrong brown (7.5YR4/6); light fine sandy clay loam; hardsetting surface condition; moderate fine blocky structure; pH 6.5; abrupt change to:
LP86 Profile
LP86 Profile
Subsoil
B216-15 cmYellowish red (5YR4/6); medium heavy clay; moderate medium blocky, breaking down to strong very fine polyhedral structure (with smooth faced peds); very strong consistence dry; pH 7.6; clear change to:
B2215-35 cmReddish brown (5YR4/4); medium heavy clay; coarse blocky, breaking down to fine polyhedral structure (with smooth faced peds); very strong consistence dry; pH 8.5; clear change to:
B3135-60 cmStrong brown (7.5YR4/6); medium clay; moderate fine polyhedral structure (rough faced peds); contains very few (2%) carbonate nodules in patches; pH 9.2; very strong consistence dry; clear change to:
B3260-85 cmDark yellowish brown (10YR4/4) and strong brown (7.5YR4/6); light medium clay; moderate coarse polyhedral, breaking down to moderate fine polyhedral structure (rough faced peds); pH 9.1; very strong consistence dry; clear change to:
B3385-100 cmYellowish brown (10YR5/6); fine sandy light clay; contains many dark flecks (manganese); pH 9.2; gradual change to:
B34100+ cmYellowish brown (10YR5/5); fine sandy light clay; pH 9.0.

Key Profile Features
  • Strong texture contrast between surface (A1) horizon (20% clay) and subsoil (B21) horizon (53% clay).
  • Sodic subsoil.

Key Profile Characteristics

pH
Salinity Rating
Surface
(A1 horizon)
slightly acid
very low
sodic
slight-moderate1
Subsoil
(B21 horizon)
slightly alkaline
very low
sodic
strong
Deeper subsoil
(at 1 m)
strongly alkaline
low-medium
strongly sodic
strong
1 Complete dispersion with remoulding.

LP86 Graphs

Horizon
Horizon Depth
pH (water)
pH CaCl2
EC 1:5
NaCl
Exchangeable Cations
Ca
Mg
K
Na
meq/100g
A1
0-6
6.5
5.2
0.07
1.7
1.9
0.5
0.3
B21
6-15
7.6
6.5
0.17
4.4
6.3
0.9
1.7
B22
15-35
8.5
7.2
0.2
4.9
7
0.7
2.5
B31
35-60
9.2
8.5
0.49
<0.05
4.3
7
0.5
2.6
B32
60-85
9.1
8.5
0.67
0.05
3.4
6.3
0.5
3.1
B33
85-100
9.2
8.4
0.59
0.05
4.8
11
1.2
5
B34
100+
9
8.3
0.72
<0.05
5.4
15
1.5
7.2

Horizon
Horizon Depth
Ex Al
mg/kg
Ex Ac
meq/100g
Field
pF2.5
Wilting Point
pF4.2
Coarse Sand
(0.2-2.0mm)
Fine Sand
(0.02-0.2mm)
Silt
(0.002-0.02mm)
Clay
(<0.002mm)
A1
0-6
24.5
7.5
1
43
34
20
B21
6-15
29.2
17.1
1
20
21
53
B22
15-35
30.2
16.9
1
27
24
48
B31
35-60
31.1
17.1
0
37
27
37
B32
60-85
B33
85-100
B34
100+


Management Considerations:

Whole Profile

  • Plant Available Water Capacity (PAWC) is considered to be low (estimated at 85 mm) for this site. This is based on available laboratory data and assumes an effective rooting depth of 50 cm. Rooting depth will be limited by the strongly sodic subsoil.

Surface (A) Horizon
  • Due to previous soil loss under a different manager, the surface horizon is very shallow and does not provide much of a buffer zone to the sodic subsoil. Minimising further soil loss should be a prime objective.
  • The surface horizon is hardsetting when dry and has a high fine sand (43%) and silt (34%) content. When cultivated dry, the soil will become "powdery" and the structure will break down. Tillage should be minimised and stubble retention/pasture rotations practised to build up organic matter levels. Organic carbon levels are moderate at this site. Improving organic matter levels will assist in minimising structural problems as well as improving soil fertility and water holding capacity.
  • The surface horizon is sodic and disperses slightly to moderately. After remoulding, it disperses completely which suggests that excessive cultivation or overstocking of the soil in a moist to wet condition may result in the development of surface crusting and exacerbate the hardsetting condition. Raindrop action on bare soil will have a similar effect. Due to surface sealing, water infiltration will be reduced and seedling emergence restricted. Gypsum is usually an effective ameliorant on such soils. The use of gypsum will improve surface infiltration as well as seedling emergence.

Subsoil (B) Horizons
  • The upper subsoil is strongly sodic and has a low calcium:magnesium ratio (i.e. <1). As a consequence it disperses strongly in water. This is likely to result in water and root movement being significantly restricted.
  • The salinity rating becomes low to medium from 60 cm. This may restrict the growth of salt sensitive species (e.g. maize, linseed and faba beans).
  • The subsoil is strongly alkaline (from 35 cm depth) which indicates that some nutrients (e.g. phosphorus, iron, manganese and zinc) may be poorly available to plants.

Comments from Landholder:
  • Topsoil lost in the 1982 drought, (under a different manager).
  • Stubble retention and direct drilling used.
  • Gypsum used on neighbouring paddock with success. Infiltration of water improved significantly.
  • Was heavily cropped for 20 years (crop/fallow regime), under a different manager.

Notes
  • Profile described by Mark Imhof, Paul Rampant and Karen De Plater (5/7/95)
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