SW18a

Location: Glenormiston College (North Farm).

Australian Soil Classification: Vertic, Subnatric, Brown SODOSOL
Northcote Factual Key: Dy1.23
Great Soil Group: solodic

General Landscape Description: Level Plain.
Site Description: Reserve at the edge of a grazing paddock.
Geology: Quaternary basalt (Qvn).

SW18a Landscape

Soil Profile Morphology:

Surface Soil

A1	0-20 cm	Very dark brown (10YR2/2); fine sandy clay loam; weak consistence dry; pH 5.1; gradual change to:
A2	20-30 cm	Dark brown (10YR3/3); clay loam (fine sandy); firm consistence slightly moist; pH 5.7; gradual change to:
Subsoil
B21	30-50 cm	Brown (10YR4/3); medium heavy clay; moderate blocky, parting to fine blocky structure; firm consistence moist; pH 6.3; clear change to:
B22	50-70 cm	Very dark grey (10YR3/1); heavy clay; moderate coarse blocky structure; firm to very firm consistence moist; pH 7.1:
B23	70-100 cm	Brown (10YR4/3) with a slight yellowish brown (10YR5/4) mottle; heavy clay; firm to very firm consistence moist; contains a few (2-5%) manganese flecks and basalt rocks (30 cm in size); slickensides present; pH 8.2

• Strong texture contrast between surface (A) horizon (29% clay) and the sodic subsoil (B21) horizon (46% clay).
• Vertic properties i.e. significant shrink-swell characteristics in the subsoil.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly Acid	Low	Non-Sodic	None
Subsoil (B21 horizon)	Slightly Acid	Very Low	Sodic	Strong 1
Deeper subsoil (at 80 cm)	Moderately Alkaline	Low	Strongly Sodic	Strong 1

The surface soil is strongly acid. The subsoil is slightly acid becoming moderately alkaline at 80 cm.	The salinity rating is low becoming low to moderate at 80 cm.	The surface is non-sodic. The subsoil is sodic becoming strongly sodic at 70 cm.	The clay content gradually increases with depth.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC dS/m	Organic Carbon %	Total Nitrogen %	Exchangeable Cations				Coarse Sand (0.2-2.0 mm) %	Fine Sand (0.02-0.2 mm) %	Silt (0.002-0.02 mm) %	Clay (<0.002 mm) %	Wilting Point % w/w
							Ca	Mg	K	Na
							meq/100g
A1	0-20	5.1	4.7	0.2	5.6	0.57	6.2	5.6	1.4	0.58	7	28	22	29	25
A2	20-30	5.7	5.1	0.12	2.8	0.24	5.4	6.1	1.3	0.66	8	32	21	30	18
B21	30-50	6.3	5.3	0.11			6.1	9.9	1.6	1.7	8	26	15	46	24
B22	50-70	7.1	6	0.18			8.5	15	1.6	4.1	4	21	14	56	28
B23	70-100	8.2	7.2	0.4			9.9	20	1	6.5	4	20	13	48	29

• Plant available water capacity (PAWC) is considered to be low-medium (estimated at 96 mm). This is based on available laboratory data and assumes an effective rooting depth of 70 cm. Rooting depth will be restricted by the dense and strongly sodic subsoil. The availability of moisture to the plant depends to a large degree on soil structure and consistence. In dense and coarsely structured subsoils such as these, it is likely that there will be a large amount of unused ‘available’ moisture in the subsoil.