MM104

Site code	MM104
Location	Deans Marsh (Salt Creek Lane), Colac district, south-west Victoria
Landform	Gently undulating rises
Geology	Palaeogene: Eastern View Formation: fluvial sand, gravel, clay, brown coal
Element	Crest

Profile morphology

Horizon	Depth (cm)	Description
A1	0–25	Dark brown (10YR3/3); fine sandy loam; apedal massive structure; weak consistence (dry); clear boundary to:
A2	25–55	Brown (10YR5/3), conspicuously bleached, light grey (10YR7/2 dry); fine sandy loam; weak consistence (dry); very many fine to coarse segregations; sharp boundary to:
B21	55–80	Dark brown (10YR3/3) with red (2.5YR4/6) mottles; heavy clay; strong coarse blocky structure; very firm consistence (dry); gradual boundary to:
B22	80+	Yellowish brown (10YR5/6) with red (2.5YR4/6) mottles; medium clay; moderate medium blocky structure; very firm consistence (moderately moist).

ASC: Eutrophic; Mottled-Subnatric; Brown Sodosol

Analytical data Source: Government of Victoria, State Chemistry Laboratory.

Site MM104	Sample depth	pH		EC	NaCl	Ex Ca	Ex Mg	Ex K	Ex Na	Ex Al	Ex acidity
Horizon	cm	H₂O	CaCl₂	dS/m	%	cmol_c/kg	cmol_c/kg	cmol_c/kg	cmol_c/kg	mg/kg	cmol_c/kg
A1	0–25	5.5	N/R	0.05	N/R	1.4	1.4	0.1	0.3	N/R	12.8
A2	25–55	6.1	N/R	0.03	N/R	1	1	0	0.3	N/R	4.7
B21	55–80	7.2	N/R	0.15	N/R	3	3	0.2	3.5	N/R	10.3
B22	80+	7.3	N/R	0.1	N/R	2.8	2.8	0.2	3.6	N/R	11.3

Site MM104	Sample depth	FC (-10kPa)	PWP (-1500kPa)	KS	FS	Z	C	Org C	Bulk density
Horizon	cm	%	%	%	%	%	%	%	t m^-3
A1	0–25	23.9	12.2	3	64	13	14	2.9	1.11
A2	25–55	N/R	N/R	6	70	14	10	0.8	N/R
B21	55–80	50.3	35.3	2	11	4	83	N/R	1.18
B22	80+	N/R	N/R	1	8	1	90	N/R	N/R

Management considerations
This soil has a very strong texture contrast between the fine sandy loam surface, subsurface soil and the medium to heavy clay subsoil. There is some depth (55cm) before the clay is reached which acts as a throttle to water and gases. Restricted water movement is also evident by the bleached A2 horizons (or subsurface soils). These bleached horizons may act as conduit for subsurface flow, particularly on sloping ground. If the soil is dispersive then gypsum application would be suitable, while increasing organic matter and maintaining vegetative cover is important.

The subsoil is mottled and sodic. These sodic subsoils usually have poor structure (generally as coarse domed columns). The poor structure results in dispersion (and subsequent clogging of pores), restricting water and gas movement through the subsoil, as evidenced by the mottling. These soils are hardsetting and have limited opportunity for cultivation without further damage to soil structure. The application of gypsum is used to counter the effect of the sodicity. Penetration by deep-rooted crops is also useful as is minimum tillage practices which avoids bring the sodic, dispersive material to the surface.

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