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River flats (Symbol: rm)

EG213 | EG9 | EG119 | EG121

Geology
Recent alluvium, mainly comprising fine sand, silt and clay.

Landform
Broad alluvial plain. This map unit includes all modern flood plain deposits of the various rivers.


Genoa River flats, between Genoa and Gipsy Point

Native vegetation
Riparian forest.

Soils
All of the soils examined had slightly to moderately acidic very dark grey to very dark greyish brown clay loam silty clay loam to clay loam surface soils which became lighter in colour with depth as the level of organic matter decreased. The coarse sand contents through the profile were very low.

Site EG213

Location: Cann River flats	Geo. Ref. 0691100E 5846300N
Australian Soil Classification: Vertic (Mottled-Sodic), Eutrophic, Grey DERMOSOL	Grey uniform textured soil
General landscape description: Alluvial plain
Geology: Recent sediments
Site description: Level plain >1% slope
Land use: Grazing
Native vegetation: Riparian forest
Mapping unit: River flats (rf)

Soil profile morphology

Surface soil
A11	0 – 15 cm	Very dark greyish brown (10YR3/2); silty clay loam; moderate fine (2 - 5 mm) granular structure; weak consistence moist; diffuse change to:
A12	15 – 35 cm	Dark greyish brown (10YR4/2); silty clay loam; weak medium (10 – 20 mm) polyhedral structure; firm consistence moist; diffuse change to:
Subsoil
B21	35 – 70 cm	Dark greyish brown (10YR4/2) with common distinct medium yellowish brown (10YR5/6) mottles; silty clay; moderate coarse polyhedral structure; very firm consistence moist; change to:
B22	70 – 110 cm	Grey (10YR5/1) with common distinct medium yellowish brown (10YR5/6) mottles; light clay; moderate coarse lenticular structure; very firm consistence moist.
Key profile features Lack of strong texture contrast between the surface (A11 & A12) horizons and the subsoil (B1) horizon. Coarsely structured deep subsoil.

Soil profile characteristics

	pH	Salinity rating	Sodicity	Dispersion	Slaking
Surface soil (A11 horizon)	Slightly acid	Low	Non sodic	None	Slakes considerably
Subsoil (B21 horizon)	Slightly acid	Very low	Sodic	Strong	Slakes considerably
Deeper subsoil (70 -110 cm)	Moderately alkaline	Very low	Strongly sodic	Strong	Slakes considerably

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	0-15	ZCL	6.4	6.2	0.27	6	24	36	20	41.3	18.9	22.4
A12	15-35	ZCL	5.9	5.1	0.09	6	23	36	28	33.3	15.1	18.2
B21	35-70	ZC	6.4	5.5	0.15	4	26	34	31	29.1	15.3	13.8
B22	70-110	MC	8.3	7.0	0.17	0	33	28	34	32.0	18.1	13.9

* 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 % w/w	Exch. Al	Exchangeable cations cmol(+)/kg							Ca:Mg	ESP
cm	%	%		ppm	Ca	Mg	K	Na	Total	H	CEC
0-15	4.8	0.39		<10	14.0	3.1	0.44	0.13	16.7	11.0	27.7	4.5	1
15-35	1.7	0.07		26	3.5	3.9	0.062	0.59	8.1	12.0	20.1	0.9	3
35-70	0.73			<10	1.5	6.1	0.07	1.8	9.5	7.8	17.3	0.2	10
70-110	0.44				1.3	9.1	0.066	3.7	14		14	0.1	26

# Organic carbon

Management considerations

• Plant available water capacity (PAWC) is considered to be moderate-high (estimated at 65 mm) for this soil profile. This is based on an estimated effective rooting depth of 60 cm (i.e. surface soil and upper subsoil). The denser and more coarsely structured deeper subsoil is likely to restrict rooting depth.
• Infiltration of water will be rapid throughout the upper soil profile due to the well developed structure and pore space available.

Surface (A) Horizons

• The relatively deep surface soil is moderately well structured and is friable when moist. Soil consistence when moist is also weak for this horizon. As a result of these attributes the surface soil will provide excellent seed-bed conditions, creating few limitations to root and water movement.
• The surface (A1) horizon has a moderate nutrient holding capacity (based on the sum of the exchangeable calcium, magnesium and potassium cations).
• The surface soil has moderate potassium content and no response to potassium fertilizer would be expected. However below this depth, the level of potassium is very low.
• The surface soil has high organic matter content. Soils such as these rely on organic matter to maintain soil structure. Maintaining organic matter levels will also assist in improving soil fertility and water holding capacity.
• Infiltration of water into the well structured surface soil will be quite high and this horizon will be well drained.

Subsoil (B) Horizons

• The deep subsoil is sodic and coarsely structured which will significantly restrict deeper root and water movement.

Site EG9

Location: Orbost River flats	Geo. Ref. 0634100E 5821200N
Australian Soil Classification: Melanic, Eutrophic, Black DERMOSOL	Black uniform textured soil
General landscape description: Alluvial plain
Geology: Recent sediments
Site description: Level plain >1% slope
Land use: Grazing
Native vegetation: Riparian forest
Mapping unit: River flats (rf)

Soil profile morphology

Surface soil
A11	0 – 25 cm	Very dark grey (10YR3/1); clay loam; strong medium polyhedral structure, weak consistence moist; clear change to:
A12	25 – 55 cm	Black (10YR2/1); clay loam; moderate medium polyhedral structure; firm consistence moist:
Deep subsoil
D	70 – 105 cm	Very dark grey (10YR3/1); clay loam; weak to very weak coarse prismatic structure; firm consistence moist.
Key profile features Lack of texture contrast throughout the soil profile.
Soil profile characteristics pH Salinity rating Sodicity Dispersion Slaking Surface soil (A11 horizon) Moderately acid Very low Non sodic None Slakes partially Subsoil (50-57 cm) Slightly acid Very low Non Sodic None1 Slakes partially Deeper subsoil (70 -105 cm) Slightly acid Very low Non Sodic None2 Slakes partially

¹ Moderate after remoulding (20 hrs)
² Complete after remoulding (20 hrs)

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	0-25	CL	5.9	5.0	0.12	1	28	30	35	40.6	23.3	17.3
A12	25-55	CL	6.3	5.3	0.07	1	27	33	29
A13	55-70	CL	6.4	5.4	0.08	2	28	33	29
D	70-105	CL	6.7	5.5	0.07	1	34	31	29

Sampled by auger

Depth	Org C#	Total N	Free Fe2O3	Exch. Al	Exchangeable cations cmol(+)/kg							Ca:Mg	ESP
cm	%	%	% w/w	ppm	Ca	Mg	K	Na	Total	H	CEC
0-25	2.8	0.25		<10	7.6	6.4	0.84	0.96	15.8	14	30.0	1.2	3
25-55	2.5	0.19		<10	10.0	7.1	0.22	0.63	18	14	32.0	1.4	2
55-70	2.2	0.14		<10	8.8	7.9	0.19	0.78	17.7	13	31.0	1.2	3
70-105				<10	6.9	8.3	0.15	0.84	16.2	9.5	25.5	0.9	3

# Organic carbon; Sampled by auger

Management considerations

• There are no impeding layers in the profile which allows plant roots deep penetration.

Surface (A11) Horizons

• The relatively deep surface soil is moderately well structured and is friable when moist. Soil consistence when moist is also weak for this horizon. As a result of these attributes the surface soil will provide excellent seed germination conditions and few other limitations to root and water movement.
• The nutrient holding capacity of this soil is high (based on the sum of the exchangeable calcium, magnesium and potassium cations)
• Potassium levels are high and no response to potassium fertilizer would be expected. However below 25 cm the levels are quite low.

Subsoil Horizons

• The subsoil is non-sodic and reasonably well structured. Root and water movement will not be significantly restricted as a result.

Site EG119

Location: Orbost South	Geo. Ref. 631500E 5824200N
Australian Soil Classification: Melanic, Eutrophic, Black DERMOSOL	Black uniform textured soil
General landscape description: Alluvial plain
Geology: Recent sediments
Site description: Level plain >1% slope
Land use: Grazing
Native vegetation: Riparian forest
Mapping unit: River flats (rf)

Soil profile morphology

Surface soil
A11	0 – 30 cm	Very dark greyish brown (10YR3/2); clay loam, (high in organic matter); strong medium polyhedral structure; weak consistence moderately moist; gradual change to:
A12	30 – 70cm	Dark greyish brown (10YR4/2) distinctly mottled with fine common dark brown (7.5YR3/4) mottles ; fine sandy clay loam; moderate medium polyhedral structure; weak consistence moist; clear change to:
D	70 – 110cm	Very dark grey (10YR3/1); silty clay loam; weak to moderate coarse prismatic structure; firm consistence moderately moist.
Key profile features Uniform textures throughout.
Soil profile characteristics pH Salinity rating Sodicity Dispersion Slaking Surface soil (A11 horizon) Slightly acid Very low Non sodic None1 Slakes partially Subsoil (A12 horizon) Slightly acid Very low Non sodic None2 Slakes partially Deep subsoil (D horizon) Strongly acid Very low Non sodic None Slakes partially 1 Slight after remoulding 2Strong 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	0-30	CL	6.1	5.2	0.09	0	32	39	25	35.2	20.3	14.9
A12	30-70	FSCL	6.4	5.5	0.08	0	44	26	22	30.7	14.1	16.6
D	70-110	ZCL	5.5	4.7	0.13	1	40	26	25

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

Depth	Org C#	Total N	Free Fe2O3	Exch Al	Exchangeable cations meq/100 g							Ca:Mg	ESP
cm	%	%	% w/w	ppm	Ca	Mg	K	Na	Total	H	CEC
0-30	2.2	0.24		11	8.1	5.5	0.5	0.53	14.6	12.0	27.0	1.5	2
30-70				11	8.5	5.9	0.21	0.56	14.6	9.2	24.2	1.5	2
70-110				42	4.6	4.0	0.22	0.62	9.4	16.0	25.5	1.2	2

# Organic carbon; Sampled by auger

Management considerations

• The plant available water content of this soil is moderate (65 mm based a rooting depth of 70 cm).

Surface soil (A horizons)

• The deep surface soil is well structured
• Infiltration of water into the well structured surface soil would be quite high. This horizon is also very well drained
• The nutrient holding capacity of the soil is high (based on the sum of the exchangeable cations)
• Potassium levels are moderate to high and any response to potassium fertilizer is unlikely
• The soil is slightly acid and unlikely to respond to lime.

Site EG121

Location: Cann River Flats	Geo. Ref. 692200E 5849100N
Australian Soil Classification: Melanic, Sodic, Eutrophic, Grey DERMOSOL	Grey uniform textured soil
General landscape description: Alluvial plain
Geology: Recent sediments
Site description: Level plain >1% slope
Land use: Grazing
Native vegetation: Riparian forest
Mapping unit: River flats (rf)

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Soil profile morphology

Surface soil
A11	0 – 30 cm	Very dark grey (10YR3/1); clay loam, high in organic matter; strong medium polyhedral structure; very weak consistence moist; gradual change to:
A12	30 – 50 cm	Dark greyish brown (10YR4/2) distinctly mottled with fine common dark brown (7.5YR3/4) mottles; silty clay loam; moderate medium polyhedral structure; weak consistence moist; gradual change to:
Subsoil
B2	50 – 70 cm	Brown (10YR5/3) with many medium faint dark greyish brown (10YR4/2) mottles; silty clay; weak to moderate coarse prismatic structure; firm consistence moist ; diffuse change to:
Deep subsoil
D	70 – 105 cm	Dark greyish brown (10YR4/2) with common distinct medium brown (7.5YR5/4) mottles; sandy clay loam; weak coarse polyhedral structure; firm consistence moist.
Soil profile characteristics pH Salinity rating Sodicity Dispersion Slaking Surface soil (A11 horizon) Moderately acid Very low Non sodic None Slakes partially Subsoil (A12 horizon) Strongly acid Very low Non sodic None1 Slakes partially Deep subsoil (B2 horizon) Moderately acid Very low Non sodic Slight2 Slakes partially 1 Slight after remoulding; 2 Complete after remoulding and 20 hrs Sampled by auger

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	0-30	CL	5.6	4.9	0.08	6	31	30	23	33.4	14.0	19.4
A12	50-70	ZCL	5.4	4.7	0.09	7	32	34	25
A13	70-105	ZCL	5.9	5.0	0.11	7	26	34	31

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

Depth	Org C#	Total N	Free Fe2O3	Exch. Al	Exchangeable cations meq/100 g							Ca:Mg	ESP
cm	%	%	% w/w	ppm	Ca	Mg	K	Na	Total	H	CEC
0-30	2.9	0.21		14	7.5	1.4	0.17	0.24	9.4	15.0	24.4	5.4	1
50-70				48	3.3	2.4	0.12	0.28	6.1	12.0	18.1	1.4	2
70-105				12	2.8	4.9	0.13	0.62	8.5	8.2	16.7	0.6	4

# Organic carbon; Sampled by auger