LS15

Location: Netherby

Australian Soil Classification: Hypercalcic, Hypernatric, Red SODOSOL

Northcote Factual Key: Db 1.33
Great Soil Group: solonetz

General Landscape Description: Upper slope on the northern spur of a subdued north-south trending rise. Slopes are generally 2-3%.

LS15 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-15 cm	Dark brown (10YR3/3); sandy clay loam; weakly structured; weak consistence dry; pH 7.7:	LS15 Profile
A2	15-20 cm	Reddish brown (5YR4/4) sporadically bleached; sandy clay loam; strong consistence dry; pH 7.9; clear change to:
Subsoil
B21	20-30 cm	Reddish brown (7.5YR4/4); medium clay; strong medium to coarse prismatic, parting to strong medium blocky structure; strong consistence moist; pH 8.9:
B22	30-50 cm	Dark red (2.5YR3/6); heavy clay; moderate medium prismatic, parting to strong medium blocky structure; very strong consistence dry; pH 9.3:
B23	50-75 cm	Yellowish red (5YR5/6); light medium clay; structure similar to above; firm consistence moist; contains many (20 - 50%) soft calcareous segregations; pH 9.3:
B24	75-160 cm	Light yellowish brown (10YR6/4) with yellowish brown (10YR5/8) and strong brown (7.5YR4/6) mottles; sandy clay; moderate coarse prismatic, parting to coarse polyhedral structure; strong consistence moist; pH 9.2:
C	160+ cm	Weathered sandstone.

Key Profile Features:

• Strong texture contrast between surface (A) and subsoil (B21) horizon.
• Hardsetting nature of surface soil.

Soil Profile Characteristics:

	pH	Salinity	Sodicity	Dispersion
Surface (A1 horizon)	Slightly Alkaline	Low	Non-Sodic	None
Subsoil (B21 horizon)	Strongly Alkaline	Low-Medium	Strongly Sodic	Complete
Deeper Subsoil (at 1 metre)	Very Strongly Alkaline	High	Strongly Sodic	Complete

The surface soil is strongly acid. The subsoil becomes very strongly alkaline at depth.

The salinity rating is low in the surface. The subsoil is low becoming high with depth.

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

Chemical and Physical Analysis:

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC dS/m	Sodium Chloride %	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
A1	0-15	7.7	7.3	0.35	<0.05	6.3	1.7	0.8	0.2
A2	15-20	7.9	7.2	0.15		3.4	1.6	0.4	0.3
B21	20-30	8.9	8	0.46	<0.05	7.6	9.2	1.2	7.3
B22	30-50	9.3	8.6	0.94	0.11	6.5	11.6	1.5	10.4
B23	50-75	9.3	8.6	1.19	0.19	5.8	10.4	1.2	9.6
B24	75-160	9.2	8.4	1.02	0.16	5.2	10.2	1	10.4

Horizon	Horizon Depth (cm)	Total Nitrogen %	Oxidisable Organic Carbon %	Field Capacity pF2.5	Wilting Point pF4.2
A1	0-15	<0.05	0.6	12.9	7.2
A2	15-20			11.5	4.8
B21	20-30			43.8	24.9
B22	30-50			40.5	25.5
B23	50-75
B24	75-160

Management Considerations:

Surface (A) Horizon

• Building up organic matter levels will assist in improving soil fertility, water holding capacity and aggregate stability. Practices such as residue retention, minimum tillage and including pasture rotations should be utilised if cropping occurs.
• The subsurface (A2) horizon seems to be developing a cultivation pan layer, which may restrict root and water movement. This horizon is also slightly sodic. Mechanical disturbance (e.g. cultivation) when in a moist to wet condition is likely to promote the development of a cultivation pan (as indicated by dispersion occurring after remoulding).

Subsoil (B) Horizons

• The strongly sodic and dispersive subsoil is likely to restrict water and root movement at 20 cm and below. The sporadic bleaching that occurs above this horizon shows that water movement is being restricted by the subsoil. Deep ripping with gypsum application has been advocated by some researchers as an ameliorative technique for sodic subsoils. A test strip could be used to assess likely benefits. Ripping should not be carried out, however, if the soil is in a moist to wet condition.
• Subsoil salinity levels are likely to affect sensitive species from 30 cm depth in the profile.
• The subsoil from 30 cm is strongly alkaline. This indicates that some nutrients (e.g. iron, manganese, copper and zinc) may be poorly available to plants at depth. Plant tissue analysis can be used to determine if difficulties occur.

Comments from Landholder:

• Superphosphate applied regularly.
• Gypsum applied 1993.
• Nitrogen applied.
• Peas/wheat/chickpeas/barley and faba beans are grown in rotation.

Profile Described By: Mark Imhof, John Martin, David Rees, Austin Brown, Geof Morrow, Sonia Thompson (May 1994).