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Tambo (Symbol: Tb)

EG261 | EG262 | EG263 | EG264 | EG265

Geology
Ordovician sediments.

Landform
Rolling to steep low hills. Elevation range 40 – 540 m with local relief generally 30 – 90 m and slope gradients up to 32%, but typically 8 - 20%.

The Tambo map unit may be subdivided into three components: upper slopes and broad rounded crests, mid-slopes, lower slopes and open depressions.

Original vegetation Shrubby dry forest. Soils Component 1: Soils on crests and upper slopes Rock occurs in these soils generally within 1 m. The soils appear to be mostly texture contrast soils with some gradational soils on the crest and upper-most slopes. The surface soils are generally dark brown strongly acidic loams to fine sandy loams abruptly overlying brown to reddish brown acidic medium clays. Decomposing Ordovician sediments, generally mudstone, occurs before 1 m. Gradational soils appear to occur when the depth to rock is less than 0.5 m. (See Wiseleigh pit 1, Bruthen and Clifton Creek.). Component 2: Soils on mid-slopes Rock occurs in these soils around 1 m or deeper. The soils are also texture contrast soils, with the surface soils being strongly acidic dark brown loams and overly brown to reddish brown acidic medium clays. (See Wiseleigh pit 2.). Component 3: Soil on lower slopes and open depressions These soils are mostly formed on colluvium and locally derived alluvium eroded from up-slope and redeposited. The soils are likely to be quite variable, but the surface soils are likely to be dark greyish brown acidic loams. (See Wiseleigh pit 3.) These soils are likely to be sodic and dispersive with depth with the risk of gully and tunnel erosion developing. Land use Much of the area defined by this unit is uncleared but there are substantial areas cleared and used for grazing.

Shallow soils on Ordovician sediments in road cutting near Clifton Creek

Site EG261

Location: Bruthen	Geo. Ref.: 575500E 5825000N
Australian Soil Classification: Melacic, Eutrophic, Brown DERMOSOL	Brown gradational soil
General landscape description: Rolling to steep low hills
Geology: Ordovician sediments
Site description: Upper slope
Land use: Grazing on annual pasture
Native vegetation: Valley dry forest
Map unit: Tambo (Component 1)

Soil profile morphology

Surface soil
A11	0 – 12 cm	Dark yellowish brown; fine sandy clay loam; few (10%) small angular pebbles (<20 mm); clear wavy change to:
A12	12 – 35 cm	Yellowish brown; fine sandy clay loam (heavy); common (10-20%) angular pebbles (<60 mm) increasing with depth; gradual change to:
A13	35 – 60 cm	Light brown; fine sandy clay loam (heavy); many (20-50%) angular pebbles and cobbles (<200 mm) increasing in size and amounts with depth; passing to:
R	60+ cm	Weak rock becoming stronger with depth

Key profile features

• Uniform textures to at least 60 cm.

Soil profile characteristics

	pH	Sodicity	Slaking	Dispersion Dry	Dispersion Remoulded
Surface soil (A11 horizon)	Strongly acid	Non-sodic	Water stable	Nil (2 hours), Nil (20 hours)	Nil (2 hours), Nil (20 hours)
Subsurface (A12 horizon)	Strongly acid	Non-sodic	Partial	Nil (2 hours), Nil (20 hours)	Slight (2 hours), Moderate (20 hours)
Deeper subsoil (35 – 60 cm)	Strongly acid	Non-sodic	Partial	Nil (2 hours), Nil (20 hours)	Moderate (2 hours), Moderate (20 hours)

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
A11	0-12	FSL	5.4	4.7	0.07	16	30	26	17	37.6	12.1	25.5
A12	12-35	FSCL	5.2	4.4	<0.05	15	32	31	18	27.1	8.6	18.5
A13	35-60	FSCL	5.3	4.4	<0.05	17	33	28	21	22.1	8.3	13.8

* PAW refers to plant available water. This is the difference between the soil’s 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
0-12	5.7	0.35		71	7.1	1.8	0.4	<0.1	9.4	17	26.4	4
12-35				200	1.4	1.3	0.3	<0.1	3.1	13	16.1	1.1
35-60				190	0.9	1.8	0.2	<0.1	3	9.1	12.1	0.5

# Organic carbon

Management considerations

Whole profile

• The brown colours throughout and lack of texture contrast indicate the profile is well drained internally.
• The soil texture is almost uniform throughout.

Surface (A11) horizon

• The soil has a high organic matter content conferring good structural stability.
• The nutrient holding capacity of the soil is moderate (based on the sum of exchangeable cations).
• The potassium levels are marginal but the soil is unlikely to show a response to potassium fertilisers at this stage.

Subsurface soils

• The presence of increasing amounts of rock in the subsoil is likely to restrict root development.

Site EG262

Location: Clifton Creek	Geo. Ref.: 556640 5827970N
Australian Soil Classification: Sodic, Dystrophic, Yellow CHROMOSOL	Yellow sodic texture contrast soil (shallow)
General landscape description: Undulating to rolling low hills
Geology: Ordovician sediments
Site description: Mid-slope, north aspect, 10 % slope
Land use: Grazing
Native vegetation: Shrubby dry forest
Map unit: Tambo (Component 2)

Soil profile morphology

Surface soil
A1	0 – 5 cm	Dark brown (10YR3/2); loam; weak fine subangular blocky structure; firm dry; abrupt change to:
Subsoil
B21	5 – 20 cm	Brown (7.5YR4/2), light brown (7.5YR6/3) dry; medium clay (subplastic); moderate coarse prismatic structure; firm dry; few (<10%) angular medium pebbles (<20 mm); clear change to:
B22*	20 – 30 cm	Brown (7.5YR4/2), few coarse reddish yellow (7.5YR6/6) mottles; light clay; moderate coarse prismatic structure; common (10-20%) angular stones (200-600 mm); clear change to:
C	30 -70 cm	Yellowish brown (10YR5/4); light clay; massive; abundant (>90%) angular soft rock.
*This horizon is discontinuous

Key profile features

• Shallow depth of surface soil.
• Marked increase in soil texture between the A1 and B21 horizon.
• Shallow depth to soft decomposing rock.

Soil profile characteristics

	pH	Sodicity	Slaking	Dispersion (Dry)	Dispersion (Remoulded)
Surface soil	Strongly acid	Non-sodic	Water stable	Nil (2 hours), Nil (20 hours)	Slight (2 hours), Slight (20 hours)
Subsoil (B22 horizon)	Moderately acid	Sodic	Water stable	Nil (2 hours), Slight (20 hours)	Moderate (2 hours), Moderate (20 hours)
Deep subsoil (C horizon)	Slightly alkaline	Non-sodic	Partial	Moderate (2 hours), Moderate (20 hours)	Strong (2 hours), Strong (20 hours)

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
0-5	0-5	L	5.1	4.4	5.1	21	29	20	14	36.4	17.4	19
5-20	5-20	MC	5.7	4.7	5.7	18	28	7	41	26.9	10.3	16.6
20-30	20-30	LC	6.7	5.3	6.7	17	26	28	25	24.1	10.8	13.8
30-70	30-70	LC	7.6	6.4	7.6	19	18	38	23	21	10.3	10.7

* PAW refers to plant available water. This is the difference between the soil’s 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
0-5	8.3	0.6		140	3.2	2.1	0.3	0.2	5.8	21	26.8	1.6	<0.1
5-20	2.3	0.11		100	0.3	1.2	<0.1	0.4	2	12	14.0	0.3	3
20-30				13	0.1	2.6	0.1	0.6	3.4	6.1	9.5	<0.1	6
30-70				<5	<0.1	3.4	<0.1	0.3	3.9	1.7	5.6	<0.1	5

# Organic carbon

Management considerations

Whole profile

• On the assumption the roots can extract the water in the top 25 cm of the soil, the plant available water capacity is estimated at 38 mm. The high amounts of organic matter in this surface soil have added to the soil’s ability to retain water.

Surface (A) horizons

• The surface soil is strongly acidic but in the subsoil it is moderately acidic. Lime is unlikely to show any economic benefit.
• Potassium is deficient and a response to potassium fertiliser is likely. This would particularly apply if the pasture was removed and baled.
• The nutrient holding capacity of the soil is low (based on the sum of the basic cations) and the depth of surface soil is shallow.

Subsoil (B) horizons

• Based on the sum of the basic cations, the subsoil has a very low nutrient holding capacity.
• The subsoil is non-sodic and only slightly dispersive. Given the presence of increasing amounts of rock down the profile, gully and tunnel erosion is unlikely.

Wiseleigh Pits (EG263, EG264, EG265)


Sequence of soil pits examined at Wiseleigh

Site EG263

Location: Wiseleigh	Geo. Ref.: 570600E 5826400N
Australian Soil Classification: Melacic, Dystrophic, Brown KUROSOL	Brown texture contrast soil
General landscape description: Rolling low hills
Geology: Ordovician sediments
Site description: Pit 1: Upper south slope, 15% slope
Land use: Grazing
Native vegetation: Grassy woodland
Map unit: Tambo (Component 1)

Soil profile morphology

Surface soil
A11	0 – 5 cm	Black (10YR2/1); loam; strong fine granular structure; weak consistence moderately moist; wavy change to:
A12	5 – 30 cm	Dark brown (7.5YR3/2); loam; moderate fine subangular blocky structure; firm consistence moderately moist; few (2-10 %) angular pebbles (20-60 mm) of parent rock; wavy change to:
Subsoil
B2	30 – 50 cm	Dark reddish brown (5YR3/2); medium clay; weak fine polyhedral structure; firm consistence moderately moist; common (10-20%) angular pebbles (20-60 mm) of parent rock; wavy change to:
C	50 – 70 cm	Brown (7.5YR4/3); sandy loam; massive; firm consistence moderately moist; abundant (50-90%) angular pebbles and cobbles (<200 mm) mm) of parent rock; wavy change to:
R	100 cm+	Weak rock becoming stronger with depth

Key profile features

• Texture contrast between the surface (A) horizons and the subsoil (B horizons).
• Very high organic matter in the surface soil, which enhances nutrient and water-holding capacity.

Soil profile characteristics

	pH	Sodicity	Slaking	Dispersion (Dry)	Dispersion (Remoulded)
Surface soil (A11)	Very strongly acid	Non-sodic	Minimal aggregation	Minimal aggregation	Minimal aggregation
Subsoil (B2 horizon)	Very strongly acid	Non-sodic	Water stable	Nil (2 hours), Nil (20 hours)	Nil (2 hours), Nil (20 hours)
Deep subsoil (C horizon)	Strongly acid	Non-sodic	Water stable	Nil (2 hours), Nil (20 hours)	Nil (2 hours), Nil (20 hours)

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
A11	0-5	L	4.8	4.2	0.13	27	27	7	23	51.7	27.4	24.3
A12	5-30	L	4.8	4.2	0.05	23	24	23	21	41.6	13.2	28.4
B2	30-50	MC	5	4.4	<0.05	29	23	2	44	34.1	10.4	23.7
C	50-70	SL	5.1	4.7	<0.05	40	18	26	16	21.7	7.1	14.6

* PAW refers to plant available water. This is the difference between the soil’s 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
0-5	14	0.77		220	5.5	2.6	0.7	<0.1	8.8	21	29.8	2.1	<1
5-30	4.6	0.18		500	0.5	0.4	0.2	<0.1	1.1	22	23.1	1.3	<1
30-50	2.2	0.1		240	<0.1	0.1	0.1	<0.1	0.2	15	15.2		<1
50-70				92	<0.1	<0.1	<0.1	<0.1		5.3	5.3		<1

# Organic carbon

Management considerations

Whole profile

• On the assumption the roots can extract the water in the top 50 cm of the soil, the plant available water capacity is estimated at 56 mm. The high amounts of organic matter in this surface soil have added to the soil’s ability to retain water.

Surface (A) horizons

• The surface soil is very strongly acidic and the high levels of exchangeable aluminium are likely to restrict the growth of aluminium sensitive species. A response to lime would be expected, but before it is applied, test strips should be used to evaluate the cost/benefit.
• The nutrient holding capacity of the immediate surface soil is moderate (based on the sum of the basic cations) largely due to its high organic matter content. The immediate subsurface soil has an extremely low nutrient holding capacity.

Subsoil (B) horizons

• Based on the sum of the basic cations, the subsoil has an extremely low nutrient holding capacity.
• The subsoil is non-sodic and not dispersive. Given the presence of increasing amounts of rock down the profile, gully and tunnel erosion in this particular soil is unlikely.

EG264

Location: Wiseleigh	Geo. Ref.: 570600E 5826400N
Australian Soil Classification: Melacic, Magnesic (and Dystrophic), Brown CHROMOSOL	Brown texture contrast soil
General landscape description: Gently undulating plain
Geology: Ordovician sediments
Site description: Pit 2: Mid south slope, 17% slope
Land use: Grazing
Native vegetation: Grassy woodland
Map unit: Tambo (Component 2)

Soil profile morphology

Surface soil
A11	0 – 8 cm	Very dark grey (7.5YR3/1); loam; strong fine granular structure; firm consistence dry; abrupt change to:
A12	8 – 35 cm	Very dark grey (7.5YR3/1); clay loam; weak fine angular blocky structure; firm consistence dry ; clear change to:
Subsoil
B21	35 – 50 cm	Brown (7.5YR5/4) medium clay; moderate coarse (50 – 100 mm) prismatic structure; firm consistence dry; few (2 – 10%) angular pebbles (< 60 mm); gradual change to:
B22	50 – 70 cm	Light brown (7.5YR6/4); light clay; moderate coarse (50 – 100 mm) prismatic structure; very firm consistence dry; few (2 – 10%) angular pebbles (< 60 mm); gradual change to:
C	70 – 100 cm	Mottled yellow (10YR7/6) and reddish yellow (5YR6/6); light clay; strong medium (10 – 20 mm) polyhedral structure; very firm consistence dry; diffuse change to:
R	100 cm+	Weak decomposing rock

Key profile features

• Texture contrast between the surface (A) horizons and the subsoil (B horizons).
• Very high organic matter in the surface soil, which enhances nutrient and water-holding capacity.

Soil profile characteristics

	pH	Sodicity	Slaking	Dispersion (Dry)	Dispersion (Remoulded)
Surface soil (A11)	Very strongly acid	Non-sodic	Minimal aggregation	Minimal aggregation	Minimal aggregation
Subsoil (B21 horizon)	Moderately acid	Non-sodic	Partial	Nil (2 hours), Nil (20 hours)	Nil (2 hours), Slight (20 hours)
Deep subsoil (C horizon)	Slightly acid	Sodic	Partial	Slight (2 hours), Moderate (20 hours)	Strong (2 hours), Complete (20 hours)

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
A11	0-8	L	4.9	4.2	0.12	24	23	19	19	53.1	30	23.1
A12	8-35	CL	5.0	4.3	<0.05	17	24	23	28	53.0	15.2	37.8
B21	35-50	MC	5.8	4.7	<0.05	18	22	13	44	34.4	14.1	20.3
B22	50-70	LC	5.8	4.7	<0.05	22	21	27	28	29.3	12.4	16.9
C	70-100	LC	6	4.6	<0.05	8	16	46	29	35.5	14.7	20.8

* PAW refers to plant available water. This is the difference between the soil’s 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
0-8	11	0.59		360	3.4	3.2	0.9	0.1	7.6	18	25.6	1.1	<1
8-35	5.3	0.22		460	0.2	0.7	0.2	0.1	1.2	20	21.2	0.3	<1
35-50				140	<0.1	0.7	0.2	0.1	1.1	13	14.1	<0.1	<1
50-70				82	<0.1	0.7	0.1	<0.1	1	6.1	7.1	<0.1	<1
70-100				55	<0.1	1.3	0.2	0.2	1.8	4.2	6.0	<0.1	11

# Organic carbon

Management considerations

Whole profile

• Based on a plant root depth of 50 cm, the plant available water capacity is about 62 mm.
• Texture contrast between the surface (A horizons) and the subsoil (B horizon).

Surface (A) horizons

• The surface (A11) horizon has a particularly high organic matter content which has greatly added to the nutrient holding and water holding capacity of the soil. By contrast the subsurface soil (A12) horizon has a very low nutrient holding capacity.
• The surface soil is very strongly acidic and the very high levels of exchangeable aluminium are likely to restrict the growth of aluminium sensitive species. A response to lime would be expected, but before it is applied, test strips should be used to evaluate the cost/benefit.

Subsoil (B and C) horizons

• All of these horizons have a very low nutrient holding capacity (based on the sum of the calcium, magnesium, potassium and sodium cations).
• The deep subsoil (C horizon) is sodic and shows moderate dispersion after 20 hours of wetting. Such a soil would be prone to tunnel and gully erosion.

EG265

Location: Wiseleigh	Geo. Ref.: 570600E 5826300N
Australian Soil Classification: Sodic, Magnesic (and Dystrophic), Brown DERMOSOL	Brown gradational soil
General landscape description: Gently undulating plain
Geology: Colluvium derived from further up-slope
Site description: Pit 3: Lower south-south east slope, 12%
Land use: Grazing
Native vegetation: Shrubby dry forest
Map unit: Tambo (Component 3)

Soil profile morphology

Surface soil
A11	0 – 10 cm	Very dark grey (7.5YR3/1); loam; moderate fine subangular blocky structure; firm consistence dry; clear change to:
A12	10 – 55 cm	Dark brown (7.5YR3/2); fine sandy light clay; moderate fine subangular blocky structure; firm consistence dry; clear change to:
A2	55 – 65 cm	Light yellowish brown (10YR6/4); fine sandy clay loam; massive; very firm consistence dry; few (2-10%) angular quartz gravel (6-20 mm); clear change to:
Subsoil
B2	65 – 85 cm	Yellowish red (5YR4/6); fine sandy clay loam; moderate coarse (50 – 100 mm) angular blocky structure; strong consistence dry; few (2-10%) angular quartz gravel (6-20 mm); clear change to:
C1	85 – 120 cm	Yellowish red (5YR4/6); fine sandy light clay; weak fine angular blocky structure; very firm consistence dry; few (2-10%) angular quartz gravel (6-20 mm); gradual change to:
C2	1.2 – 1.9 m	Pale brown (10YR6/3); light clay; strong medium (10 – 20 mm) polyhedral structure; very firm consistence dry; diffuse change to:
C3	1.9 – 2.4 m	Dark reddish grey (5YR4/2); light medium clay; few (2-10%) angular quartz gravel (6-60 mm).

Key profile features

• Deep dark coloured surface horizons indicate a high organic matter content and high water retention properties.
• It is likely much of the surface soil has been derived from further upslope post-clearing.

Soil profile characteristics

	pH	Sodicity	Slaking	Dispersion (Dry)	Dispersion (Remoulded)
Surface soil (A11)	Very strongly acid	Non-sodic	Minimal aggregation	Minimal aggregation	Minimal aggregation
Subsoil (B2 horizon)	Slightly acid	Non-sodic	Considerable	Moderate (2 hours), Moderate (20 hours)	Strong (2 hours), Strong (20 hours)
Deep subsoil (C2 horizon)	Slightly alkaline	Sodic	Considerable	Strong (2 hours), Strong (20 hours)	Strong (2 hours), Strong (20 hours)

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
A11	0-10	L	5.1	4.4	0.08	23	24	21	18	44.7	23.2	21.5
A12	10-55	FSLC	5.4	4.5	<0.05	18	28	7	39	42.9	12.5	3.4
A2	55-65	FSCL	6	4.8	<0.05	25	34	21	18	21	8.1	12.9
B2	65-85	FSCL	6.2	4.9	<0.05	24	30	21	23	20.3	9.2	11.1
C1	85-120	FSLC	6.6	5.1	0.05	21	27	19	33	25.9	11.5	14.4
C2	120-190	LC	7.7	6.1	0.06	23	29	18	30	22.8	9.6	13.2
C3	190-240	LMC	8	6.8	0.2	18	21	14	45	30.1	15.4	14.7

* PAW refers to plant available water. This is the difference between the soil’s 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
0-10	9.2	0.54		26	3.6	3.2	0.1	0.5	7.4	21	28.4	1.1	2
10-55	3.5	0.16		230	0.6	0.9	0.3	0.1	1.9	21	22.9	0.7	<1
55-65				63	<0.1	0.9	<0.1	0.1	1	6	7	<0.1	1
65-85				36	<0.1	1.9	<0.1	0.3	2.2	4.6	6.8	<0.1	4
85-120				210	<0.1	2.3	0.4	0.2	2.9	3.5	6.4	<0.1	3
120-190				<5	<0.1	2.9	<0.1	0.7	3.6	2.1	5.7	<0.1	12
190-240					0.3	4.9	0.2	1.9	6.8	3.4	10.2	<0.1	19

# Organic carbon

Management considerations

Whole profile

• On the assumption the roots can extract the water in the top 65 cm of the soil, the plant available water capacity is estimated at 68 mm. The high amounts of organic matter in this surface soil have added to the soil’s ability to retain water.

Surface (A) horizons

• The surface soil is very strongly acidic and the high levels of exchangeable aluminium occurring in the subsurface soil are likely to restrict the growth of aluminium sensitive species. A response to lime may be expected, but before it is applied, test strips should be used to evaluate the cost/benefit.
• Potassium is deficient and a response to potassium fertiliser is likely. This would particularly apply if the pasture was removed and baled.
• The nutrient holding capacity of the immediate surface soil is low to moderate (based on the sum of the basic cations) largely due to its high organic matter content. The immediate subsurface soil has an extremely low nutrient holding capacity.

Subsoil (B) horizons

• Based on the sum of the basic cations, the subsoil has an extremely low nutrient holding capacity.

Deep subsoil (C) horizons

• The deep subsoils are sodic and strongly dispersive. If the soil becomes saturated there is the risk of deep tunnels and subsequent gully erosion.