LP58

LP58 Landscape

Soil Profile Morphology

Surface Soil

A1	0-7 cm	Dark yellowish brown (10YR4/4); silty clay loam; hardsetting with surface cracking; weak blocky structure; firm consistence moist; pH 6.3; clear change to:	LP58 Profile
A2	7-10 cm	Yellowish brown (10YR5/4) conspicuously bleached (10YR7/1d); fine sandy clay loam; massive; strong consistence dry; pH 6.3; gradual change to:
Subsoil
B21	10-50 cm	Yellowish brown (10YR5/4); light medium clay; strong coarse polyhedral structure; strong consistence dry; pH 8.2; gradual change to:
B22	50-90 cm	Yellowish brown (10YR5/4); light medium clay; moderate coarse blocky structure; strong consistence moist; contains a few (5%) hard calcareous nodules; pH 9.3; gradual change to:
B23	90 cm+	Yellowish brown (10YR5/4); light medium clay; strong medium to coarse polyhedral structure; strong consistence dry; pH 8.9.

• Strong texture contrast between surface (A) horizon (clay content 32%) and the top of the subsoil (B21) horizon (clay content 66%).
• Hardsetting surface soil, with high fine sand (34%) and silt (34%) content.
• Coarsely structured sodic subsoil.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	slightly acidic	very low	sodic	slight1
Subsoil (B21 horizon)	moderately alkaline	very low	strongly sodic	complete
Deeper subsoil (at 70 cm)	strongly alkaline	medium-high	strongly sodic	complete
1 Strong dispersion after remoulding.

Horizon	Horizon Depth	pH (water)	EC 1:5	NaCl	Exchangeable Cations
					Ca	Mg	K	Na
					meq/100g
A1	0-7	6.3	0.15		2.1	3.8	0.8	0.7
A2	7-10	6.3	0.1		1.9	3.9	0.5	1.2
B21	10-50	8.2	0.24		4.4	9	0.9	4.8
B22	50-90	9.3	0.97	0.14	3.5	13	1	8.6
B23	90+	8.9	0.96	0.17	3.2	11	1	10

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	0-7			27.8	10.3	1	34	34	32
A2	7-10
B21	10-50			37.4	20.8	0.3	14	22	66
B22	50-90
B23	90+

• In general, management strategies for all soils should aim to increase organic matter levels in the surface soil; minimise the degradation of soil aggregates and porosity; promote the development of stable biopores; improve the calcium status of the ion exchange complex (particularly when sodium is a significant part – i.e. sodic), and break up any hardpans. Less frequent tillage; using less aggressive implements, and working the soil at optimum moisture conditions can all assist in maintaining soil aggregation and porosity as well as reducing the breakdown of organic matter. Practices such as residue retention, minimum tillage and including pasture rotations could be utilised if cropping takes place in order to build up organic matter, reduce erosion risk and increase fertility.
• Plant available water capacity (PAWC) is estimated to be low (estimated at 65 mm) for this profile - based on the laboratory data available. Effective rooting depth will be limited by the strongly sodic subsoil.

• The surface soil has a low overall nutrient status (based on the sum of the exchangeable basic cations).
• The surface soil is sodic and disperses slightly in water. However, when remoulded it disperses strongly which indicates that over cultivation or overstocking of the soil in a wet condition may result in dispersion and crust formation occurring. The hardsetting condition will also be exacerbated.
• Improving surface soil organic matter levels will assist in minimising structural problems such as crusting and dispersion as well as improving soil fertility and water holding capacity.

• The top of the subsoil is strongly sodic (and also has a low calcium:magnesium ratio) and disperses completely in water. This is likely to result in restricted water and root movement through the profile. The conspicuously bleached surface (A2) horizon indicates that water movement is being restricted and that periodic waterlogging may occur.
• The subsoil salinity rating becomes medium at 50 cm depth in the profile. This may restrict the growth of salt sensitive species (e.g. maize and many legumes).