IS14

Location: Murtoa

Morphological Soil Type: Drung Sandy Clay Loam

Australian Soil Classification: Calcic, Subnatric, Red SODOSOL

Northcote Factual Key: Dr 2.33
Great Soil Group: red-brown earth
Mapping Unit: Drung Sandy Clay Loam


General Landscape Description: Crest of a slight rise in the prior stream flood plain landscape.
Site Description: Cleared and cultivated area.
Geology: Late Tertiary to Quaternary Shepparton Formation.
Native Vegetation: Probably originally Buloke (Casuarina luehmannii) vegetation.

IS14 Landscape

Soil Profile Morphology:

Surface soil

A1	0-5 cm	Dark brown (7.5YR3/4); fine sandy clay loam; plastic; hardsetting surface condition; weak coarse angular blocky structure; strong consistence dry, moderately sticky consistence wet; pH 7.8; sharp and wavy change to:	IS14 Profile
A2	5-10 cm	Brown (7.5YR4/3) sporadically bleached (10YR7/1); fine sandy clay loam; weak coarse blocky structure; pH 8.1; sharp and wavy change to:
Subsoil
B21	10-25 cm	Reddish brown (5YR4/4); light clay; plastic; moderate coarse prismatic structure; strong consistence dry, moderately sticky consistence wet; pH 8.7; sharp and wavy change to:
B22	25-45 cm	Yellowish red (5YR4/6); light clay; plastic; moderate coarse prismatic structure; strong consistence dry, moderately sticky consistence wet; pH 9.3; clear and wavy change to:
B231k	45-90 cm	Strong brown (7.5YR5/6) with faint yellowish red (5YR4/6) fine mottles; medium clay; plastic; weak blocky structure; strong consistence dry, moderately sticky consistence wet; contains very few (< 2 %) hard carbonates and a few (2-10%) soft carbonates; pH 9.3:
B232k	90-130+ cm	Strong brown (7.5YR5/6) with faint yellowish red (5YR4/6) fine mottles; medium clay; plastic; weak blocky structure; strong consistence dry, moderately sticky consistence wet; contains very few (< 2 %) hard carbonates and a few (2-10%) soft carbonates; pH 9.3.

Key Profile Features:

• Strong texture contrast between surface (A) horizons (< 24% clay) and subsoil (B21) horizon (56% clay).

Soil Profile Characteristics:

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Slightly Alkaline	Low	Non-Sodic	None1
Subsoil (B21 horizon)	Strongly Alkaline	Low	Sodic	Slight
Deeper Subsoil (at 1 m)	Very Strongly Alkaline	High	Very Strongly Sodic	None2

¹ Moderate dispersion after remoulding. ² Due to high levels of soluble salts.

The surface soil is slightly alkaline. The upper subsoil is strongly alkaline becoming very strongly alkaline with depth.

The salinity rating is low in the surface and upper subsoil becoming high with depth.

The surface is non-sodic. The upper subsoil is sodic becoming very strongly sodic with depth.

The clay content jumps markedly at the surface subsoil boundary.

Chemical and Physical Analysis:

Horizon	Sample Depth cm	pH H2O	EC dS/m	Sodium Chloride %	Exchangeable Calcium cmol-/kg	Exchangeable Magnesium cmol-/kg	Exchangeable Potassium cmol-/kg	Exchangeable Sodium cmol-/kg	Total Nitrogen %	Organic Carbon %	Bulk Density	Exchangeable Acidity cmol-/kg	Field Capacity -30okPa	Permanent Wilting Point -1500okPa	Coarse Sand %	Fine Sand %	Silt %	Clay %
A1	0–5	7.8	0.11	0.01	7	3.8	0.7	0.6	0.09	1.22	1.28	2.7	19.6	8.4	20	45	8	24
A2	5–10	8.1	0.07	0.01	4.7	3.4	0.4	0.9	0.06	0.75		2		6.7	22	48	9	20
B21	10–25	8.7	0.18	0.03	10	12.5	1.6	3.9	0.08	0.68	1.26	1.3		23.3	12	24	5	56
B22	25–45	9.3	0.48	0.06	9.4	17.1	1.6	6.8	0.06	0.47	1.28			26.7	6	17	4	69
B31k	45–90	9.3	1.03	0.13	6	13.3	1.5	8	0.03	0.25	1.45			23.3	9	20	5	55
B32k	90–130	9.3	1.17	0.18	5.2	12.6	1.4	7.8	0.02	0.13				20.1	13	22	7	47
B233	130–190	9.2	1.11	0.16										20.3	12	22	9	53
B234	190–230	8.6	1.05	0.17										21.1	11	26	7	54

Management Considerations:

Whole Profile

• Plant available water capacity (PAWC) is considered to be relatively low (estimated at 79 mm). This is based on available laboratory data and assumes an effective rooting depth of 45 cm. Effective rooting depth will be restricted by the strongly sodic deeper subsoil which has a high level of soluble salts.

Surface (A) Horizons

• The surface soil disperses moderately after remoulding. This indicates that cultivation or overstocking of the soil when in a wet condition may result in dispersion and consequent structural degradation (eg. exacerbated hardsetting, surface sealing, cloddiness) occurring.
• The surface soil has a high fine sand content (ie. 45%) and is hardsetting when dry. Soils such as these rely to a large extent on organic matter for maintaining aggregation. Organic matter will build up under pasture but will decline if cultivation takes place. 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.
• The subsurface (A2) horizon is sodic and is likely to disperse significantly after remoulding. This indicates that if tillage occurs when this horizon is in a wet condition, a plough pan may develop. Gypsum application on such soils may assist in improving soil structural condition.

Subsoil (B) Horizons

• The coarsely structured subsoil becomes strongly sodic from 25 cm depth, and has a low exchangeable calcium to magnesium ratio (ie. < 0.6). This is likely to result in restricted root and water movement in the subsoil. The presence of a conspicuous bleach in the A2 horizon indicates that water movement into the subsoil is being restricted.
• The high level of exchangeable sodium and magnesium in the subsoil may also result in nutrient imbalances and may even have a toxic effect on some plants.
• The strongly alkaline subsoil indicates that some nutrients (eg. manganese, iron, copper, zinc) may be poorly available to plants.
• The level of soluble salts becomes high from 45 cm depth. This is likely to restrict the growth of salt sensitive species (eg. faba beans, chickpeas, lupins).

Profile Described By: John Martin, Nabil Badawy, Ron Cawood, Geoff Pope, John Galea, John Turner (1970).

Reference: "Major Agricultural Soils of the Wimmera Irrigation Area". John Martin, Mark Imhof, Lourey Ruth, Rob Nink, Karen DePlater, Paul Rampant, Sonia Thompson, S. Alexander. Department of Natural Resources and Environment, Victoria. 1996.