Walnut (Symbol: Wn)

EG201 | Profile No. 22 (Aldrick et al, 1992)

Geology
Holocene and Pleistocene alluvium.

Landform
Level plain with slopes generally less than 1% with a relief <9 m.

Terraced alluvial floors at low elevation, comprising flood plains, older alluvial terraces and alluvial fans, stream channels.

These terraces are confined to the Tambo River and its tributaries, mostly between 300 and 500 m.


Tambo valley flood plain north of Swifts Creek

Original vegetation
Dry valley forest.

Soils
Component 1: Soils on flood plains
Most of the soils of this map unit occur on the flood plains. Generally they are dark greyish brown deep fine sandy to silty loams and clay loams, but layers of coarser material such and stones and gravel may occur deeper in the subsoil (Site EG201). Parts of the valley have been dredged for gold bringing the stones to the surface.

Component 2: Soils on the older alluvial terraces
Older alluvial terraces are a minor component of this map unit and where they do occur are above the level of the current flood plain. The surface soils are commonly very dark greyish brown loamy sands to sandy clay loams overlying brown or reddish brown subsoils with variable texture and structure. No pits have been dug on this component.

Component 3: Soils on the alluvial fans.
These are a very minor component of this map unit and would vary greatly in colour, texture and rock fragments.

Component 4: The stream channel.
Bed and bank erosion is common along the stream channels.

Site EG201

Location: Swifts Creek	Geo. Ref. 0563288E 5877374N
Australian soil classification: Melanic, Eutrophic, Brown DERMOSOL	Dark brown uniform textured soil
General landscape description: Valley flat
Geology: Recent alluvium
Site description: Level
Land use: Grazing on annual pasture
Native vegetation: Dry valley forest
Mapping unit: Walnut (Component 1)

Soil Profile Morphology

Surface soil
A11	0 – 20 cm	Dark brown (10YR3/3); silty clay loam; strong fine (2 – 5 mm) granular structure; firm consistence dry; clear change to:
A12	20 – 45 cm	Very dark greyish brown (10YR3/2); silty clay loam; strong fine (2 – 5 mm) granular structure; firm consistence dry; diffuse change to:
A13	45 – 85 cm	Dark brown (10YR4/3); fine sandy clay loam; weak fine (2 – 5 mm) granular structure; firm consistence dry; clear change to:
Deep subsoil (buried soil)
D	85 – 105+ cm	Very dark grey (10YR3/1); clay loam; moderate medium (5 – 10 mm) polyhedral structure; firm dry
Key profile features Little colour or texture changes down the soil profile. Well structured upper profile.

Soil profile characteristics

	pH	Salinity rating	Sodicity	Dispersion	Slaking
Surface (A1 horizon)	Strongly acid	Very low	Non sodic	None	Water stable
Subsoil (A12 horizon)	Slightly acid	Very low	Non sodic	None	Slakes partially
Deeper subsoil (D horizon)	Slightly alkaline	Very low	Non sodic	None	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	0-20	ZCL	5.5	4.9	0.12	5	42	26	19	35.4	10.9	24.5
A12	20-45	ZCL	6.5	5.7	0.05	12	38	25	19	33.3	10.3	20.0
A13	45-85	FSCL	7.2	6.4	<0.05	8	46	24	18	30.4	9.1	21.3
D	85-105	CL	7.5	5.8	0.05	3	26	37	27	40.1	15.6	24.5

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

Depth	Org C#	Total N	Free Fe2O3 % w/w	Exch. Al	Exchangeable cations meq/100 g							Ca:Mg	Na %
cm	%	%		ppm	Ca	Mg	K	Na	Total	H	CEC
0-20	3.3	0.26		<10	7.6	1.6	0.99	0.084	10.2	8.3	18.5	4.9	<1
20-45	2.1	0.12			9.3	1.9	0.29	0.14	11.6	4.4	16.0	4.9	1
45-85	0.95				9.2	2.7	0.18	0.22	12.3		12.3	3.4	2
85-105	1.8				14	5.3	0.25	0.37	19.9		19.9	2.6	2

# Organic carbon

Management considerations

Whole profile

• Plant available water capacity is considered to be low. This is based on an estimated effective rooting depth of 85 cm (i.e. the surface soil and the upper subsurface soil).

Surface (A1) horizon

• The relatively deep surface soil is well structured.
• Infiltration of water into the well structured surface soil will be quite high. This horizon is also very well drained.
• The nutrient holding capacity of the surface (A1) horizon is moderate (based on the sum of the exchangeable cations). The organic matter for this soil is high which adds in both water and nutrient holding capacity.

Subsurface (A12 and A13) horizons

• The upper subsurface soil is also well structured.

Profile No. 22 (Aldrick et al, 1992)

Location: Swifts Creek	Geo. Ref. 0563300E 5877800N
Australian soil classification: Humose, Eutrophic, Brown DERMOSOL	Dark brown uniform textured soil
General landscape description: Valley flat
Geology: Recent alluvium
Site description: Level
Land use: Grazing on annual pasture
Native vegetation: Dry valley forest. Mostly Yellow Box, some Manna Gum
Mapping unit: Walnut (Component 1)

No photo available.

Soil Profile Morphology

Surface soil
A0	0 – 7 cm	Loam; moderate crumb structure; abundant roots; abrupt wavy boundary to:
A11	4 – 11 cm	Dark brown (10YR3/3); fine sandy clay loam; apedal; slightly hard dry; abundant roots; abrupt wavy boundary to:
A12	11 – 44 cm	Very dark greyish brown (10YR3/2); fine sandy clay loam; apedal; common roots; clear wavy boundary to:
Subsoil
C1	44 – 87 cm	Dark brown to brown (10YR4/3); sand; apedal; 60 % fine gravel (3 mm); wavy boundary to:
C2	87 – 97 cm	Dark brown to brown (10YR4/3); sand; apedal; 60 % fine gravel (3 mm); wavy boundary to:
C3	97 – 107+ cm	Very dark brown (10YR3/2) with common distinct yellowish brown mottles; silty clay loam; apedal; soft consistence dry.

Key profile feature

• Little colour or texture changes down the soil profile

Soil profile characteristics

	pH	Salinity rating	Sodicity	Dispersion	Slaking
Surface (AO horizon)	Strongly acid	Low But harmless	Non sodic
Subsurface (A11 horizon)	Slightly acid	Very low	Non sodic
Deeper subsurface (A12 horizon)	Slightly alkaline	Very low	Non sodic

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
A0	0-7	L	5.4		0.38	0	26	16	17
A11	4-11	FSL	6.4		0.12	2	53	21	21
A12	11-44	FSCL	7.3		0.08	3	51	21	18
C1	44-87	SL	8.0		0.56	10	69	5	8
C2	87-97	S				10

Depth	Org C#	Total N	Free Fe2O3 % w/w	Exch. Al	Exchangeable cations meq/100 g							Ca:Mg	Na %
cm	%	%		ppm	Ca	Mg	K	Na	Total	H	CEC
0-7	22.0	1.74	0.9		14.7	4.7	2.1	0.1	21.6	38.8	60.4	3.1
4-11	2.7	0.23	1.5		9.4	2.4	1.6	0.1	13.5	8.0	21.5	3.9
11-44	1.0	0.10	1.5		7.8	2.3	1.0	0.1	11.2	4.6	15.8	3.4
44-87			1.4		3.9	1.0	1.0	0.1	6.0	2.3	7.3	3.9
87-97

# Organic carbon