Ambyne (Symbol: Ae)

EG224 | EG242 | EG246

Geology
Granite.

Landform
The Ambyne map unit encompasses rolling hills at an elevation range of about 200 to 800 m and a relief range of up to 300 m.

The granitic hills between Suggan Buggan and Cabanandra have been subdivided into the Ambyne map unit, which has slopes generally less than 32% and the Tubbut map unit, with slopes generally greater than 32%.

The Ambyne map unit may be subdivided into three components: gentle to moderate slopes, crests and concave open depressions.

Cleared lower slopes near the Snowy River crossing near Suggan Buggan

Native vegetation
In the western part of the area, the native vegetation was mostly grassy dry forest, tending to grassy woodland west of Ambyne Crossing.

Land use
Mostly native vegetation, some land has been cleared for grazing.

Soils
Component 1: Soils on gentle to moderate slopes
The three soil profiles (EG224, EG242 and EG246) examined all had a high coarse sand component being described as coarse sandy loams to coarse sandy clay loam. Where the decomposing granite occurs at a shallow depth, the soils appear to be less acid with surface pH’s around 7.0. Where the depth to decomposing granite is deeper, the soils tend to be strongly to moderately acidic. This is probably because they are more deeply weathered.

Components 2 and 3: crests and concave open depressions.
No soil profiles were examined, but it is likely that those on the crests will be shallower and have occurrences of exposed rock.

Site EG224

Location: Ambyne	Geo. Ref. 0636700E 5900700N
Australian Soil Classification: Haplic, Eutrophic, Red CHROMOSOL	Red coarse sandy gradational soil
General landscape description: Rolling hills
Geology: Granite
Site description: Simple upper slope 15% south east
Land use: Grazing
Native vegetation: Grassy woodland
Mapping unit: Ambyne (Component 1)

Photo taken about 1.5km north-west of Ambyne Crossing looking south-east along the Deddick River valley

Soil profile morphology

Surface soil
A11	0 – 18 cm	Dark reddish brown (5YR3/3); coarse sandy loam; weak fine (2 – 5 mm) granular structure; weak consistence dry; pH 7.2; clear change to:
A12	18 – 40 cm	Yellowish red (5YR4/6); coarse sandy loam; weak medium (10 – 20 mm) polyhedral structure; firm consistence dry; pH 7.3; abrupt change to:
Subsoil
B2	40 – 70 cm	Dark red (2.5YR3/6); coarse sandy clay loam; moderate coarse (20 – 50 mm) polyhedral structure; strong consistence dry; passing to very weak rock; pH 6.3; diffuse change to:
C	70+	Weak granitic rock becoming more frequent with depth.
Key profile features Lack of strong texture contrast between the surface (A) and subsoil (B) horizon. Shallow depth to decomposing granite.

Soil profile characteristics

	pH	Salinity rating	Sodicity	Dispersion	Slaking
Surface soil (A1 horizon)	Slightly alkaline	Very low	Non sodic	None	Slakes partially
Subsoil (B1 horizon)	Slightly alkaline	Very low	Non sodic	None1	Slakes considerably
Deeper subsoil (80-110 cm)	Slightly acid	Very low	Non sodic	None	Slakes considerably

¹ Slight after remoulding.

Horizon	Depth cm	Field texture	pH water	pH CaCl2	EC dS/m	Coarse sand %	Fine sand %	Silt %	Clay %	Field cap. % w/w	Wilt. point % w/w	PAW* water % w/w
A1	0-18	CSL	7.2	6.3	<0.05	50	25	9	14	18.3	4.9	13.4
A2	18-40	CSL	7.3	6.2	<0.05	47	26	11	15	16.6	4.6	12.0
B2	40-70	CSCL	6.3	5.0	<0.05	40	20	14	22	22.2	9.0	13.2

* PAW is plant available water. This is the difference between the soil water content at field capacity and wilting point.

Depth	OrgC#	Total N	Free Fe2O3	Exch. Al	Exchangeable cations cmol(+)/kg							Ca:Mg	ESP
cm	%	%	% w/w	ppm	Ca	Mg	K	Na	Total	H	CEC
0-18	1.1	<0.05		<10	4.6	1.3	0.37	<0.05	6.3		6.3	3.6
18-40	0.37	<0.05		<10	2	2	0.36	0.064	4.4		4.4	1	1
40-70	0.35	<0.05		20	4.2	4.7	0.37	0.11	9.4	5.4	14.8	0.9	1

# Organic carbon

Management considerations

Whole profile

• Plant available water capacity is considered to be low (estimated at 62 mm) for the top 65 cm of the soil profile.
• The low wilting points of each horizon to this depth (4.9, 4.6 and 9.0) indicates plants are able to use light rains when the soil is dry. Due to the low water storage capacity, plants will suffer moisture stress unless further rains occur.

Surface (A) horizons

• As mentioned above, the soils surface soils can hold little water, but plants can use light rains following a dry spell.
• The surface soil is slightly alkaline. Here the pH has no adverse implications for plant growth.
• The nutrient holding capacity of the surface horizons is low (based on the sum of the calcium, magnesium, potassium and sodium cations).
• The organic matter content of the surface soil is low. Increasing organic matter will help maintain soil fertility and water holding capacity.
• The potassium is at a moderate level for pastures and no response to added potassium would be expected.

Subsoil (B) horizon

• The slight increase in clay content is unlikely to restrict root penetration of deep rooted species until the decomposing granite is reached at about 70 cm.

Site EG242

Location: Tubbut	Geo. Ref. 0638200E 5896400N
Australian Soil Classification: Eutrophic, Red CHROMOSOL	Red texture contrast soil
General landscape description: Rolling hills
Geology: Granite
Site description: Mid slope, south-east aspect, 10% slope
Land use: Grazing
Native vegetation: Grassy dry forest
Mapping unit: Ambyne (Component 1)

Soil profile morphology

Surface soil			Road exposure down-slope from sampled site
A1 Subsoil B2	0 – 20/35 cm 20/35 - 80+ cm	Brown (7.5YR4/4); coarse sandy loam, weak fine granular structure; firm consistence dry; pH 5.5; abrupt and wavy change: Reddish brown (2.5YR4/4); medium clay; moderate coarse polyhedral structure; very firm consistence dry; pH 6.0.
Horizon Depth EC dS/m pH water pH CaCl2 Exchangeable cations cmol(+)/kg Ca:Mg ESP cm Ca Mg K Na Total H CEC A1 0-20 <0.05 5.5 4.6 2.4 1.5 0.37 0.07 4.3 6.2 10.5 1.6 B2 40-60 <0.05 6.0 5.1 6.8 8.4 0.41 0.29 16 7.4 23.4 0.8 1 Sampled by auger

Site EG246

Location: Chandlers Creek	Geo. Ref. 0694600E 5865700N
Australian Soil Classification: Bleached-Mottled, Eutrophic, Red KANDOSOL	Red coarse sandy gradational soil
General landscape description: Rolling to steep hills
Geology: Granite
Site description: Upper slope, 8% slope to north
Land use: Native forest
Native vegetation: Grassy dry forest
Mapping unit: Ambyne (Component 1)

Soil profile morphology

Surface soil
A11 A2 Subsoil B2	0 – 30 cm 30 – 60 cm 60 – 1.0+m	Pinkish grey (7.5YR6/2); coarse sandy clay loam; weak coarse granular structure; weak consistence moist; pH 5.2; gradual change to: Pinkish grey (7.5YR7/2); conspicuously bleached, coarse sandy loam; massive; weak consistence moist; gradual change to: Mottled pinkish grey, yellowish red (5YR4/6) and strong brown (7.5YR4/6); coarse sandy light clay; weak coarse polyhedral structure; firm consistence moist; pH 5.9.
Horizon Depth EC dS/m pH water pH CaCl2 Exchangeable cations cmol(+)/kg Ca:Mg ESP cm Ca Mg K Na Total H CEC A1 0-20 <0.05 5.2 4.4 1.5 1.1 0.2 0.12 2.9 0.9 3.5 1.4 3 B1 60-80 <0.05 5.9 4.6 5.7 3.7 0.25 0.34 10.0 1.2 11.0 1.5 3 Sampled from road exposure Analysed by Industry and Investment NSW (2010)