SFS5b

Location: Brewster

Australian Soil Classification: Vertic (& Sodic), Eutrophic, Brown CHROMOSOL

General Landscape Description: Undulating plain within the Victorian volcanic plains.
Site Description: Crest of a hill with gilgai microrelief - mound component.
Land Use: Raised bed cropping.
Geology: Quaternary - Newer Volcanics

SFS5b Landscape. Note: slight undulation in bed lines due to gilgai.

Surface Soil			SFS5b Profile. NOTE: the abrupt and steeply inclined boundary between the mound and depression of gilgai.
Ap	0 - 20 cm	Brown (10YR4/3); fine sandy loam; weak to very firm consistence dry; pH 5.5; abrupt change to: NOTE: highly variable and mixed material, Ap originally likely to be less than 10 cm in depth and is now dominated by apedal A2 material.
Subsoil
B21tg	20 – 70 cm	Light olive brown (2.5Y5/4) with olive yellow (2.5Y6/6) mottles; medium clay; irregular medium to coarse (40–80 mm) prismatic, parting to medium to coarse (15–40 mm) angular blocky or polyhedral structure; roots between peds; pH 6.5; clear boundary to: NOTE: contrasts with lack of roots at this depth in the depression component of the gilgai.
B22gss	70-100 cm	Olive brown (2.5Y4/4) with many yellowish brown (10YR5/6) mottles; medium heavy clay; frequent small slickensides; less well developed structure than B21; pH 7.5.

• Strong texture contrast between surface (A1) horizon and subsoils (B21) horizon.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC dS/m	NaCl %	Organic Carbon %	Nitrogen %	Exchangeable Cations
								Ca	Mg	K	Na
								meq/100g
Ap	0-20	5.5	5.1	0.31	0.02	2.9	0.27	4.1	0.8	0.6	<0.1
B21tg	20-70	6.5	5.7	0.21				6.7	12	1.5	1.6
B22gss	70+	7.5	6.6	0.3	0.03			5.1	9.7	0.7	2.4

Horizon	Horizon Depth (cm)	Exchangeable Aluminium mg/kg	Exchangeable Acidity meq/100g	Field Capacity pF2.5	Wilting Point pF4.2	Coarse Sand (0.2-2.0 mm)	Fine Sand (0.02-0.2 mm)	Silt (0.002-0.02 mm)	Clay (<0.002 mm)
Ap	0-20	<10	11	33	9.1	4.1	37.7	27.5	20
B21tg	20-70		11	51.2	28.7	0.8	10.1	7.5	78
B22gss	70+			55.3	31.1	1.1	6.2	4.5	80

• Plant available water capacity (PAWC) is considered to be high (estimated at 160 mm) in the upper 100 cm of this soil profile.

• Described by the owner as ‘crabhole country’, this slightly elevated, gently sloping land has well developed ‘gilgai’ features in the subsoil. The very variable nature of this soil is evident in material in the beds which have white A2 horizon material, buckshot, pisolitic cemented buckshot and subsoil clay all present at the ground surface. ‘Spew’ or ‘hollow units’ are elongated downslope (~10 m). ‘Puffs’ are of smaller lateral dimensions than the ‘hollows’ being 1–3 metres across. In the excavated pit, two faces were picked back. SFS5a to show deep A2 with buckshot and SFS5b to show puff unit (shallow depth to clay).

• This soil presents real problems to the agriculturalist. Water holding properties are extremely different in the ‘puff’ compared with the hollow and this is often evident in the crop. The topsoil is not well structured, disintegrates to a ‘flour’ when dry-tilled, is weak and ‘spewy’ when wet and hard set when dry. Protection of the surface with ground cover is essential to reduce the slaking and sealing effects of rain. Under high rainfall / runoff conditions this soil is potentially highly erodible. The subsoil is sodic and has a high clay content so this soil is also prone to severe waterlogging. The slope of the land and the forming of beds should alleviate this in the surface horizons but erosion is a potential hazard should the furrows carry excessive runoff.