SFS20

Location: Cressy

Australian Soil Classification: Vertic (& Calcic), Mottled-Mesonatric, Black SODOSOL

General Landscape Description: Level plain, potentially a paleo lake bed or high level swamp.
Site Description: Grazing paddock. Southern Farming Systems (SFS) trial site.
Geology: Quaternary - Newer Volcanics.

SFS20 Landscape

Surface Soil			SFS20 Profile
A1	0-5 cm	Dark greyish brown (10YR4/2); fine sandy clay loam; fine crumb structure; pH 5.4; clear boundary to intermittent A2 or B21t horizons:
A2	5-30 cm	Intermittent horizon ranging from <0.5 cm to 25 cm thickness; conspicuously bleached light gray (10YR7/1 dry); rusty root channels mottling; clay loam, fine sandy; hard set massive structure (but reflecting cracking pattern of subsoil prisms below); very firm consistence dry; medium (2-5 mm in size) buckshot and well rounded quartz; pH 5.4; abrupt change to:
Subsoil
B21t	5/30 - 40 cm	Very dark grey (10YR3/1) with few yellowish brown (10YR5/8) mottles; heavy clay; extremely coarse prismatic structure; very strong consistence dry; extremely dispersive (totally disperses in 5 minutes); pH 7.3; clear change to:
B22	40-70 cm	Brown (10YR5/3) with many yellowish brown (10YR5/8) mottles; heavy clay; less definite structure than B21 above or B23 below; sticky consistence at time of sampling; pH 8.6; gradual change to:
B23ss	70-100 cm	Light yellowish brown (2.5Y6/4); heavy clay; many coarse lenticular peds; slightly calcareous; pH 9.4; gradual change to:
B24k	100-200 cm	Light olive brown (2.5Y5/4) ; heavy clay; strong coarse lenticular and prismatic structure; fine (1-3 mm in size) buckshot throughout the matrix; very many soft carbonate segregations; pH 9.4; gradual change to:
B25ss	200+ cm	Greyish brown (2.5Y5/2) with few brownish yellow (10YR6/8) mottles as well as fine black lustrous manganiferous coatings on some ped faces; strongly pedal; frequent very large (up to 1 m in size) slickensides; pH 8.7.

• Strong texture contrast between surface (A) horizons and subsoil (B21) horizons.
• Conspicuously bleached surface (A2) horizon.

The pH in the surface is strongly acid. The pH in the upper subsoil is slightly alkaline becoming very strongly alkaline with depth.

The salinity rating is low throughout the profile.

The surface is non sodic. The subsoil is strongly sodic.

The clay content increases abruptly at the surface / subsoil interface.

Horizon	pH (water)	pH (CaCl2)	EC dS/m	NaCl	Exchangeable Cations
					Ca	Mg	K	Na
					meq/100g
A1	5.4	4.7	0.27	0.03	3.3	2.8	1.2	0.6
A2	5.4	4.5	0.12		1.6	1.8	0.27	0.88
B21	7.3	6.5	0.33	0.03	4.4	13	1.6	6.1
B22	8.6	8.0	0.56	0.05	4.3	17	1.8	9.5
B23	9.4	8.5	0.37	0.06	3.3	16	1.7	12
B24	9.4	8.5	0.51	0.20	3.4	17	1.4	12
B25	8.7	7.9	0.46

Horizon	Exchangeable Aluminium mg/kg	Exchangeable Acidity meq/100g	Oxidisable Organic Carbon %	Total Nitrogen %	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)
A1	14	15	5.5	0.48	37.9	15.9	11	35	19	23
A2	37	7.6			23.2	7.3	18	40	19	19
B21					44.7	26.4	6	17	10	62
B22					47.5	28.7	6	19	13	59
B23					47.3	26.3	8	21	19	48
B24					46.8	26.1
B25

• Plant available water capacity (PAWC) is considered to be very low (estimated at 29 mm) in the upper 20 cm of this soil profile. Effective rooting depth (ERD) is restricted to 20 cm due to due to the higly sodic (ESP>20) subsoil.
• Acid topsoil (A1 and A2) and high exchangeable aluminium will limit plant growth in this soil but this can be readily remedied with lime. The subsoil is extremely sodic (ESP = 24-35%) and highly dispersive. This soil is extremely prone to waterlogging. Subsoil conditions are unfavourable for root growth because of the sodic swelling nature of the clay and the extremely coarse structure. Gypsum application will improve subsoil permeability but the coarse structure will remain a limitation. Cropping this soil would not have good prospects without major soil improvement (e.g. use of raised beds, lime and gypsum application, controlled traffic).