LP98

Location: Mount Camel Landcare Group

Australian Soil Classification: Vertic, Subnatric, Red SODOSOL

Northocte Factual Key: Dr 2.23
Great Soil Group: Red-Brown Earth

Site Description: Closed depression on plain beneath Mt. Camel Range. Gilgai microrelief present.
Geology: Alluvial and Colluvial deposits
Natural Vegetation: Grey Box (Eucalyptus microcarpa)

LP98 Landscape

Soil Profile Morphology- LP98a

Surface Soil

A11	0-7 cm	Dark yellowish brown (5YR3/4); fine sandy clay loam; weak medium blocky structure; strong consistence dry; contains few (5%) ferruginous and angular quartz gravel; pH 6.1; abrupt change to:	LP98 Profile a
A21	7-13 cm	Dark yellowish brown (5YR4/4); clay loam (fine sandy); moderate coarse blocky structure; strong consistence dry; contains few (5%) ferruginous gravels (average size 4 mm); pH 6.2:
A22	13-20 cm	Dark yellowish brown (5YR4/6); clay loam (fine sandy); weak coarse blocky structure; strong consistence dry; contains a few (5%) gravels (average size 4 mm); pH 6.5; abrupt change to:
Subsoil
B21	20-50 cm	Dark red (2.5YR3/6); medium heavy clay; moderate coarse blocky structure; significant cracking evident when dry; very strong consistence dry; pH 6.8; gradual change to:
B22	50-80 cm	Red (2.5YR5/8); medium heavy clay; moderate coarse blocky structure; numerous slickensides; very strong consistence dry; pH 8.5; gradual change to:
B31k	80 cm+	Dark red (2.5YR4/7); medium heavy clay; moderate coarse blocky structure; slickensides; firm consistence moist; pH 8.9.

Soil Profile Morphology - LP98b

NOTE: The surface horizon varies in depth and gravel content. These variations are associated with the gilgai microrelief due to the vertic properties of the subsoil.

Surface Soil

A1	0-8 cm	Dark reddish brown (5YR3/4); fine sandy clay loam; contains a common (10%) amount of ferruginous gravel; pH 6.1; abrupt change to:	LP98 profile b
A21	8-16 cm	Reddish brown (2.5YR4/4); clay loam (fine sandy); contains a common (10%) amount of ferruginous gravel (5 mm average size); pH 6.3; sharp change to:
A22	16-30 cm	Dark yellowish brown (5YR4/6); clay loam (fine sandy); weak coarse blocky structure; strong consistence dry; contains a few (5%) gravels (average size 4 mm); pH 6.5; abrupt change to:
A23	30-45 cm	Yellowish red (5YR5/6), conspicuously bleached (5YR7/4d); clay loam (fine sandy); contains very many (45%) gravels (2-4 mm size range); pH 7; sharp and irregular change to:
Subsoil
B21	45 cm +	Red (2.5YR4/8) with strong brown (7.5YR5/6) mottles; medium clay; moderate coarse prismatic, parting to moderate coarse blocky structure; pH 7.3.

Key Profile Features

• Strong texture contrast between surface (A) horizons (<34% clay) and subsoil (B21) horizon (69% clay).
• Coarsely structured, sodic subsoil.
• Deeper subsoil has vertic properties (slickensides present).
• Variability in soil due to gilgai microrelief.

Key Profile Characteristics

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Slightly Acid	Very Low	Non-Sodic	None1
Subsoil (25-45 horizon)	Slightly Acid	Very Low	Sodic	None2
Deeper subsoil ( 80 cm+)	Strongly Alkaline	Low	Sodic	Complete
1 slight dispersion with remoulding 2 complete dispersion with remoulding

LP98a

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC dS/m	NaCl	Organic Carbon %	Total Nitrogen %	Exchangeable Cations				Coarse Sand (0.2-2.0 mm) %	Fine Sand (0.02-0.2 mm) %	Silt (0.002-0.02 mm) %	Clay (<0.002 mm) %	Field Capacity % w/w	Wilting Point % w/w
								Ca	Mg	K	Na
								meq/100g
A11	0-7	6.1	5.1	0.07		2.6	0.25	7	4.5	0.8	0.6	10	31	23	32	31.7	14.6
A21	7-13	6.2	4.9	0.05				5.6	4.1	0.5	0.6	9	32	26	34	25.4	12.7
A22	13-20	6.5	5	<0.05				3.8	3.4	0.3	0.6	10	35	24	32	22.8	11.2
B21	20-50	6.8	5.3	0.05				6	9.3	0.5	2	5	16	12	69	37.8	22.3
B22	50-80	8.5	7	0.13				7.5	21	0.7	5.2					47.6	25.8
B23	80+	8.9	8	0.42	<0.05			17	19	0.6	5.5

LP98b

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC dS/m	Exchangeable Cations				Coarse Sand (0.2-2.0 mm) %	Fine Sand (0.02-0.2 mm) %	Silt (0.002-0.02 mm) %	Clay (<0.002 mm) %	Field Capacity % w/w	Wilting Point % w/w
					Ca	Mg	K	Na
					meq/100g
A21	8-16	6.3	5.1	<0.05	6.6	4.6	0.5	0.5	10	31	25	34	25.8	13.1
A22	16-30	6.6	5.2	<0.05	3.5	3.1	0.4	0.3					21.9	10.1
A23	30-45	7	5.4	<0.05	2.1	2.9	0.7	0.2	13	36	26	26	20.1	9.1
B21	45+	7.3	5.9	<0.05	3.9	8.7	2.7	0.4	7	20	16	61	31.6	19.5

Management Considerations:

• In general, management strategies for all soils should aim to increase organic matter levels in the surface soil; minimise the degradation of soil aggregates and porosity; promote the development of stable biopores; improve the calcium status of the ion exchange complex (particularly when sodium is a significant part – i.e. sodic), and break up any hardpans. Less frequent tillage; using less aggressive implements, and working the soil at optimum moisture conditions can all assist in maintaining soil aggregation and porosity as well as reducing the breakdown of organic matter. 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, reduce erosion risk and increase fertility.

• Plant available water capacity (PAWC) is considered to be medium (estimated at approximately 150 mm) in the areas with shallower surface horizons (i.e. profile 98a). This is based on available laboratory data and assumes an effective rooting depth of 90 cm. In areas with the deeper and gravelly surface horizons (i.e. profile 98b) plant available water capacity will be significantly reduced and is considered to be low (estimated at 60 mm). An effective rooting depth of 50 cm is assumed. Rooting depth will be restricted by the high gravel content of the lower surface horizons.

Surface (A) Horizons

• The surface soil disperses moderately after remoulding. This indicates that cultivation or overstocking of the soil in a moist to wet condition may result in structural degradation (eg. surface sealing, exacerbated hardsetting) occurring. Raindrop impact on bare soil is also likely to cause structural degradation so it is important to maintain surface cover. Structural degradation will result in problems such as decreased water infiltration, friability and seedling emergence.
• The lower A horizon (i.e. 13-20 cm layer) of profile LP98a is sodic and disperses completely after remoulding. Tillage of this layer when moist to wet may result in the development of a plough pan.
• High gravel contents in some areas will result in restricted root penetration.

Subsoil (B) Horizons

• The subsoil is sodic (and has a high level of exchangeable magnesium relative to calcium) which indicates that root and water movement will be restricted somewhat by the coarsely structured subsoil. Dispersion does not occur in the upper subsoil - suggesting that permeability will be better than for Site 98.
• The subsoil displays evidence of vertic properties (i.e. significant cracking, presence of numerous slickensides) which indicates that significant shrinking and swelling occurs in wetting and drying cycles. This will cause subsoil movement and has resulted in the gilgai (‘crabholey’) microrelief at the surface. Variations in subsurface horizons has occurred as a result. These vertic properties may have implications for engineering purposes (e.g. building foundations).

Comments from Landholder:

• Has been under pasture for 3 years. Lupins and wheat were grown prior.
• Considered a good cropping soil but can become boggy in winter.
• Superphosphate and gypsum never applied.

Notes

• Profile described by Mark Imhof, Paul Rampant and Karen DePlater (28/11/95)