LP87

LP87 Landscape

Soil Profile Morphology

Surface Soil

A11	0-5 cm	Dark brown (7.5YR4/4); very finesandy clay loam;hardsetting surface condition; weak blocky structure; firm consistence moist; pH 6.1; clear change to:	LP87 Profile
A12	5-12 cm	Dark brown (7.5YR4/4) (with yellowish red (5YR4/6) mixing); very fine sandy clay loam; weak blocky structure; weak consistence moist; pH 6.4; clear change to:
Subsoil
B21	12-30 cm	Yellowish red (5YR4/6); mediumheavy clay; strong coarse blocky structure (with shiny faced peds); very firm consistence moist; pH 7.3; clear change to:
B22	30-65 cm	Yellowish red (5YR5/6); medium clay; firm consistence moist; pH 8.8; gradual change to:
B23	65+ cm	Strong brown (7.5YR5/6); mediumclay; parting to strong polyhedral structure; weak consistence moist; contains a few (<2%) carbonates (5-10 mm diameter) in pockets; pH 9.0.

• Strong texture contrast between surface (A) horizons (28% clay) and the top of the subsoil (B21) horizon (63% clay).
• Strongly sodic subsoil.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	slightly acid	low	non-sodic	slight1
Subsoil (B21 horizon)	slightly alkaline	very low	strongly sodic	moderate - strong
Deeper subsoil (at 1 m)	strongly alkaline	high	strongly sodic	moderate-strong
1 Moderate to strong dispersion after remoulding.

Horizon	Horizon Depth	pH (water)	EC 1:5	NaCl	Exchangeable Cations
					Ca	Mg	K	Na
					meq/100g
A1	0-5	6.1	5.1	0.13		2.1	3.4	0.7	0.3
A12	5-12	6.4	5.2	0.13		1.8	3.4	0.6	0.4
B21	12-30	7.3	6.2	0.15		3.4	8.5	1.3	2.5
B22	30-65	8.8	8	0.91	0.15	3.6	13	1.2	6
B23	65+	9	8.5	1.2	0.21	3.6	14	1.5	6.1

Horizon	Horizon Depth	Ex Al mg/kg	Ex Ac meq/100g	Field pF2.5	Wilting Point pF4.2	Coarse Sand (0.2-2.0mm)	Fine Sand (0.02-0.2mm)	Silt (0.002-0.02mm)	Clay (<0.002mm)
A1	0-5			25	9.6	2	41	26	28
A12	5-12			22.2	8.9	2	41	26	28
B21	12-30			32.2	19	1	20	14	63
B22	30-65			36.9	20.8	1	19	19	59
B23	65+

Management Considerations

Whole Profile

• Plant Available Water Capacity (PAWC) is considered to be relatively low (estimated at approximately 80 cm) for this site. This is based on available laboratory data and assumes an effective rooting depth of 40 cm. Rooting depth will be limited by the level of soluble salts in the deeper strongly sodic subsoil.

• Total nitrogen and organic carbon levels are reasonable (as would be expected in an area that has been in pasture for a number of years).
• When dry, the surface soil will set hard and may be difficult to work. When worked in a dry condition, it will become "powdery" and then may be prone to structural degradation from raindrop action. Improving organic matter will help improve soil structure. If cultivated in a wet condition, dispersion may occur which could result in surface sealing developing which would restrict water infiltration and seedling emergence.
• The surface (A1 horizon) soil disperses slightly in water (moderately to strongly after remoulding). This indicates that mechanical disturbance to this horizon whilst in a wet condition may result in structural deterioration and exacerbate the hardsetting condition.
• The subsurface (A12) horizon disperses strongly after remoulding. Mechanical disturbance to this horizon whilst in a moist to wet condition may result in the development of a cultivation pan.

• The coarsely structured upper subsoil is strongly sodic and has a low calcium:magnesium ratio (i.e. <1). It also disperses moderately to strongly in water. This is likely to result in water and root movement being restricted throughout the profile.
• The salinity rating becomes high at 30 cm depth. This may restrict the growth of salt sensitive species (e.g. maize, linseed and faba beans). These high levels of soluble salts may be due to seepage from a nearby channel.
• The deeper subsoil is strongly alkaline (from 30 cm depth), which indicates that some nutrients (e.g. phosphorus, iron, manganese and zinc) may be poorly available to plants.

• Profile described by Mark Imhof, Paul Rampant and Karen De Plater (6/7/95).