LP88

LP88 Landscape

Soil Profile Morphology

Surface Soil

A1	0-10 cm	Dark brown (7.5YR4/4); very fine sandy clay loam; hardsetting surface condition; weak coarse blocky structure; strong consistence dry; pH 6.2; abrupt change to:	LP88 Profile
Subsoil
B21	10-40 cm	Yellowish red (5YR4/4); medium clay; strong coarse blocky, parting to strong fine polyhedral structure (with shiny faced peds); very strong consistence dry; pH 7.9; clear change to:
B22	40-65 cm	Yellowish red (5YR5/6); medium heavy clay; firm consistence moist; pH 9.0; clear change to:
B23	65-90 cm	Yellowish brown (10YR5/6) and yellowish red (5YR5/6); medium clay; moderate fine polyhedral structure; very strong consistence dry; contains few (2%) carbonate nodules (up to 15 mm diameter); pH 9.1; gradual change to:
B24	90+ cm	Yellowish brown (10YR5/6) and strong brown (7.5YR5/6); medium clay; strong fine polyhedral structure; very strong consistence dry; contains very few (<1%) carbonate nodules (up to 30 mm diameter); pH 9.1.

• Strong texture contrast between the surface (A) horizon (26% clay) and the top of the subsoil (B21) horizon (73% clay).
• Strongly sodic subsoil.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	slightly acid	very low	sodic	slight1
Subsoil (B21 horizon)	slightly alkaline	very low	strongly sodic	strong
Deeper subsoil (at 1 m)	very strongly alkaline	medium	strongly sodic	strong
1 Strong to complete dispersion after remoulding.

Horizon	Horizon Depth	pH (water)	EC 1:5	NaCl	Exchangeable Cations
					Ca	Mg	K	Na
					meq/100g
A1	0-10	6.2	5.1	0.1		2.4	2.4	0.87	0.5
B21	10-40	7.9	6.5	0.12		6.6	9.9	1.6	3.5
B22	0-65	9	7.9	0.58	0.05	5.6	13	1.6	5.7
B23	65-90	9.1	8.3	0.99	0.12	4.8	12	1.6	6.4
B24	90+	9.1	8.3	0.99	0.14	4.6	13	1.5	6.9

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	0-10			23.6	9.4	5	39	28	26
B21	10-40			39	22.7	1	13	12	73
B22	0-65			40.1	21.8	1	14	15	69
B23	65-90			38	21.2	1	14	16	62
B24	90+

• Plant Available Water Capacity (PAWC) is considered to be relatively medium (estimated approximately at 120 mm) for this site. This is based on available laboratory data and assumes an effective rooting depth of 60 cm. Rooting depth will be restricted by the strongly sodic deeper subsoil and by the medium level of soluble salts.

• The surface soil has a low overall nutrient status and the total nitrogen and organic carbon levels are moderate. Organic matter levels will have improved after three years of pasture growth. Improving organic matter levels is important for soils with high fine sand (39%) and silt (28%) contents. Such soils with low organic matter levels will set hard on drying and become difficult to work. It may become "powdery" when worked in a dry condition.
• The surface soil is sodic and will disperse after remoulding. Excessive cultivation or overstocking of the soil in a wet condition is likely to cause dispersion and may result in the development of surface sealing and exacerbate the hardsetting condition. Gypsum is usually an effective ameliorant on such soils. The use of gypsum will result in improved water infiltration and seedling emergence.

• The coarsely structured upper subsoil is strongly sodic and disperses strongly in water. This is likely to result in water and root movement being significantly restricted. Deep tillage with gypsum application has been advocated as an ameliorative technique for some subsoils. A test strip in the paddock could be used to asses this technique.
• The salinity rating becomes medium at 65 cm. This may restrict the growth of salt sensitive species (e.g. maize and many legumes).
• The deeper subsoil (from 40 cm depth) is very strongly alkaline which indicates that some nutrients (e.g. copper, iron, manganese and zinc) may be poorly available to plants.

• Gypsum used four years ago.
• Topsoil decreased over previous summer (due to blowing off).
• Under pasture for past three years ie. lucerne, ryegrass, subclover. (cropped for three years previous).

• Profile described by Mark Imhof, Paul Rampant and Karen De Plater (5/7/95)