Victorian Resources Online (archived)

MP25

Group: Birchip Cropping Group	Location: Curyo
Australian Soil Classification: Epihypersodic, Pedal, Calcic CALCAROSOL.
General Landscape Description: Very gently undulating plain within the Culgoa Land System (Rowan and Downes, 1963).

Site MP25 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-10 cm	Dark brown (7.5YR4/4); heavy clay loam (sandy); hardsetting and massive; some surface cracking evident; very firm consistence dry; pH 8.2; sharp and wavy change to:	Site MP25 Profile
Subsoil
B21	10-20 cm	Dark brown (7.5YR4/4); medium clay; moderate medium prismatic, parting to blocky structure; strong consistence dry; pH 9.3; clear change to:
B22	20-50 cm	Brown (7.5YR5/4); medium clay; moderate medium blocky structure; strong consistence dry; contains a few soft carbonates; pH 9.7; clear change to:
B31	50-100 cm	Reddish yellow (5YR6/8); heavy clay; pH 9.9.

Soil Profile Characteristics:

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	moderately alkaline	very low	non-sodic	none¹
Subsoil (B21 horizon)	very strongly alkaline	low-medium	strongly sodic	slight
Deeper subsoil (at 75 cm)	extremely alkaline	low-medium	strongly sodic	strong

¹ Strong dispersion after remoulding.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl₂)	EC ds/m	NaCI %	Exchangeable Cations				Field Capacity pF 2.5	Wilting Point pF 4.2	Coarse Sand (0.2 - 2.0 mm)	Fine Sand (0.02 -0.2 mm)	Silt (0.002 -0.02 mm)	Clay (<0.002 mm)
						Ca	Mg	K	Na
						meq/100g
A1	0-10	8.2	7.6	0.15		14.9	5.6	2	0.9	33	12	28	27	4	34
B21	10-20	9.3	8.4	0.44	<0.05	12.3	12.6	1.6	5.9	47	22	24	15	4	45
B22	20-50	9.7	9	0.76	0.05	5.8	16	2	12.1	57	24
B31	50-100	9.9	9.1	0.64	<0.05	4.3	13.8	1.7	12

Management Considerations:

Surface (A) Horizon

Although non-sodic, the surface soil disperses significantly after remoulding. This indicates that structural degradation (e.g. surface sealing, crusting, increased cloddiness) may occur if the soil is cultivated or overstocked in a moist to wet condition. Also, raindrop action on bare surface soil may also promote dispersion and result in surface sealing or crust formation
Increasing organic matter levels will assist in improving surface soil aggregation and ameliorating the hardsetting condition. Organic matter will decline under cropping but can be improved by adopting practises such as minimum tillage, residue retention and utilising pasture rotations

Subsoil (B) Horizons

The upper subsoil is very strongly alkaline becoming extremely alkaline with depth. This indicates that phosphorus and trace elements such as iron, manganese, copper and zinc may be poorly available to plants
The subsoil is strongly sodic and dispersive. The movement of water and plant roots is likely to be restricted as a result. The high level of exchangeable magnesium will also compound the deleterious effect of exchangeable sodium on subsoil structure
The level of soluble salts is only low-medium in the deeper subsoil and is only likely to affect very salt sensitive species

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