LP52

LP52 Landscape

Soil Profile Morphology

Surface Soil

A1	0-8 cm	Dark brown (7.5YR3/4); light fine sandy clay loam; hardsetting and massive; strong consistence dry; pH 6.4; sharp change to:	LP52 Profile
A2	8-10 cm	Strong brown (7.5YR4/6), sporadically bleached; light fine sandy clay loam; massive; strong consistence dry; pH 6.6; sharp change to:
Subsoil
B21	10-30 cm	Yellowish red (5YR4/6); medium heavy clay; moderate coarse blocky structure; very firm to strong consistence dry; pH 8.7; gradual change to:
B22	30-55 cm	Yellowish red (5YR4/6); light medium clay; moderate coarse blocky structure; very firm to strong consistence dry; pH 8.2; gradual change to:
B31	55-100 cm	Yellowish brown (10YR5/6) with yellowish red (5YR5/8); light medium clay (fine sandy); strong medium polyhedral structure; firm consistence moist; contains a few (2-5%) hard carbonate nodules as well as pockets of gypsum; pH 8.9; gradual change to:
B32k	100 cm+	Brown (10YR5/3) light clay (sandy); strong medium polyhedral structure (with shiny-faced peds); firm consistence moist; contains a few (2-10%) fine-earth and hard carbonates; pH 8.9.
NOTE: This soil corresponds partly to Koga Clay Loam as mapped by Skene and Harford (1964).

• Hardsetting surface horizon (with a high fine sand content of 49%).
• Strong texture contrast between surface (A) horizons and subsoil (B) horizons. (i.e. clay percentage of A horizon is 25%, compared to 52% for the B21 horizon).
• Coarsely structured subsoil (strongly sodic).

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	slightly acidic	low	Marginally sodic	none1
Subsoil (B21 horizon)	strongly alkaline	medium	strongly sodic	complete
Deeper subsoil (at 1 m)	strongly alkaline	high-very high	strongly sodic	_
1 Strong dispersion after remoulding.

Horizon	Horizon Depth	pH (water)	EC 1:5	NaCl	Exchangeable Cations
					Ca	Mg	K	Na
					meq/100g
A1	0-8	6.4	0.14		2.7	3.4	0.6	0.5
A2	8-10	6.6	0.12		2.4	3.1	0.4	0.9
B21	10-30	8.7	0.71	0.12	5.9	11	0.9	8.4
B22	30-55	8.2	0.35	0.07	5.1	7.8	0.8	4.8
B31	55-100	8.9	1.14	0.18	3.4	7.2	0.6	6.3
B31k	100+	8.9	1.74	0.3	4.1	9.3	0.7	8

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	0-8			21	10	10	49	15	25
A2	8-10			20	9.7	9	49	18	25
B21	10-30			35.2	21.4	5	32	13	52
B22	30-55
B31	55-100
B31k	100+

Management Considerations:

• 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 relatively low (estimated at 64 mm) for this profile - based on the laboratory data available. PAWC is limited by the strongly sodic subsoil and the high salinity at 55 cm.

• Surface horizon has a low overall nutrient status (based on the sum of the exchangeable basic cations)
• Surface horizon is marginally sodic and disperses strongly after remoulding. This suggests that dispersion may occur if soil is cultivated or overstocked when wet and that surface sealing may result on drying. Heavy rains falling of such soil when cultivated may also promote surface sealing and compaction. Gypsum is usually an effective ameliorant on such soils.
• Improving organic matter levels will assist in minimising structural problems such as crusting and hardsetting as well as improving soil fertility and water holding capacity.
• The subsurface (A2) horizon is sodic and completely disperses in water. It has the potential to develop into a hardpan if it is excessively worked in a wet condition.

• The coarsely structured subsoil is strongly sodic and completely disperses in water. These factors indicate that water and root movement through the profile will be restricted. (The presence of a sporadic bleach above this horizon indicates that water movement into the subsoil is restricted).
• The top of the subsoil has a medium soil salinity rating - this may restrict the growth of salt sensitive species (e.g. maize, and many legumes). The salinity rating increases with greater depth down the profile and may restrict the growth of a number of salt-sensitive species.
• The top of the subsoil is strongly alkaline, indicating that some nutrients (e.g. phosphorus, iron, manganese and zinc) may be poorly available to plants.