LWA21

Location: Birchip
Australian Soil Classification: Vertic (& Endohypersodic), Pedal, Hypercalcic CALCAROSOL (clay loamy surface soil)
General Landscape Description: Level Plain	Site Description: No-till paddock of demonstration site
Geology: Quaternary aeolian and alluvial deposits

LWA 21 Landscape

Soil Profile Morphology:

Surface Soil

A11	0-12 cm	Brown (7.5YR4/2); clay loam; weak to moderate medium (10-20 mm) sub-angular blocky, parting to weak to moderate fine (5-10 mm) polyhedral structure; very weak consistence (moderately moist); moderately calcareous effervescence fine earth; abrupt change to:	LWA 21 Profile
A21	12-18 cm	Brown (7.YR4/3); light clay (-); massive; uncemented cultivation pan, parting to moderate fine (5-10 mm) polyhedral structure; very weak consistence (moderately moist); moderately calcareous effervescence fine earth; abrupt change to:
Subsoil
B21	18-32 cm	Reddish brown (5YR5/4) with reddish brown (5YR4/3) and light brown (7.5YR6/4) mottles; light-medium clay; weak medium (20-50 mm) prismatic, parting to weak fine (10-20 mm) prismatic and weak fine (5-10 mm) polyhedral structure; weak consistence (moderately moist); high calcareous effervescence fine earth; clear change to:
B22k	32-45 cm	Brown (7.5YR5/4) with brown (7.5YR4/2) and strong brown (7.5YR4/6) mottles; medium clay; weak coarse (50-100 mm) prismatic, parting to weak coarse (20-50 mm) angular blocky structure; weak consistence (moderately moist); highly effervescent fine-earth; many (20-50%) soft calcareous segregations; gradual change to:
B23	45-80 cm	Brown (7.5YR5/4) with yellowish red (5YR5/6) and light grey (2.5YR7/2) mottles; medium clay; strong coarse (50-100 mm) prismatic, parting to strong medium (20-50 mm) prismatic and angular blocky structure; very firm consistence (dry); many (20-50%) soft calcareous segregations and few (2-10%) calcareous nodules with very few (<2%) soft manganiferous segregations; gradual change to:
B24	80-100 cm	Yellowish brown (10YR5/4) with yellowish red (5YR5/6) and light yellowish brown (2.5Y6/3) mottles; medium-heavy clay; weak coarse (50-100 mm) prismatic, parting to moderate (20-50 mm) prismatic structure; firm consistence (moderately moist); few (2-10%) soft manganiferous segregations; few distinct slickensides; diffuse change to:
B25	100-140 cm	Brown (7.5YR4/2) with light yellowish brown (2.5Y6/3) and olive grey (5Y5/2) mottles; medium-heavy clay; moderate (20-50 mm) prismatic structure; firm consistence (moderately moist), very few (<2%) soft manganiferous segregations; common distinct slickensides.

• Gradual increase in texture (i.e. clay content) with depth down the soil profile.
• Calcareous throughout (with zone of many calcareous segregations in upper soil profile)

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly alkaline	Low	Non-sodic	None
Subsoil (B21 horizon) (18-32 cm)	Very strongly alkaline	Low	Sodic	None 1
Deeper subsoil (at 110-140 cm)	Very strongly alkaline	Very high	Strongly sodic	Moderate

¹ moderate dispersion after remoulding

Horizon	Horizon Depth	pH (water)	pH CaCl2	EC 1:5	NaCl	Exchangeable Cations
						Ca	Mg	K	Na
						Meq/100g
A11	0-12	8.7	8.1	0.17		29	6.1	1.8	0.42
A21	12-18	9	8.3	0.17		28	7.4	0.98	0.99
B21	18-32	9.5	8.5	0.29	<0.02	8.6	9.7	0.76	3.1
B22k	32-45	9.8	8.8	0.64		4.1	11	0.79	6.2
B23	45-80	9.9	9.1	1	0.13	2.2	12	1.1	11
B24	80-100	9.8	9	1.3	0.18	2.1	13	1.3	13
B25	100-140	9.5	8.8	1.6	0.26	2.5	12	1.2	13

Horizon	Horizon Depth	Boron mg/kg	Field pF2.5 g/100g	Wilting Point pF4.2 g/100g	Coarse Sand (0.2-2.0mm) %	Fine Sand (0.02-0.2mm) %	Silt (0.002-0.02mm) %	Clay (<0.002mm) %
A11	0-12	2.2	32.2	13.7	30	20	6	30
A21	12-18	2.9	34.7	13.9	29	21	5	29
B21	18-32	3.9	34.1	17.8	27	18	3	30
B22k	32-45	9.2	35.7	18.7	25	16	4	29
B23	45-80	24	38.7	18.5	26	17	13	31
B24	80-100	32	44.7	21.7
B25	100-140	25

• 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) 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.

• Tillage of clayey soils like these should be avoided if the soil is wet (i.e. wetter than the plastic limit). At such moisture conditions, excessive tillage, trafficking or over-stocking could result in some structural damage (e.g. compaction). Ideally, tillage should take place on clayey soils when the soil is drier than the plastic limit – down to at least the tillage depth.

• The subsoil is very strongly to extremely alkaline throughout. This indicates that some nutrients (e.g. iron, manganese, zinc, copper) may be poorly available to plants and that deficiencies are likely to occur. Deficiencies should be determined by plant tissue analysis.
• The subsoil has a high level of soluble salts in the deeper subsoil (from 45 cm depth) that will restrict the growth of deeper rooted salt-sensitive species.
• Boron toxicity can also occur in strongly alkaline soils. Boron levels increase in the very strongly alkaline subsoil (from 30 cm depth) to levels which may affect the growth of boron-sensitive species including cereals, pulses, pasture legumes. At this site, boron levels are reasonably high (i.e. > 24 mg/kg) in the deeper subsoil. Concentrations as low as 10 ppm, for example, can reduce lentil yield. Although there is limited data it is estimated that the threshold level of soluble boron for cereals is 15 mg/kg (Cartwright et al., 1984). Previous work at DPI, Horsham has indicated that where there are low levels of soluble salts boron tolerance can be comparatively high, with little reduction in wheat yield at levels of up to 45 ppm (Quinlan, 2001).
• The upper subsoil (18-32 cm) is sodic, but does not disperse unless remoulded. It is also reasonably well structured – parting to fine polyhedral peds. This indicates that root and water movement will not be significantly restricted in the upper subsoil. However, the more coarsely structured deeper subsoil becomes strongly sodic and more dispersive – indicating that root and water movement will be restricted at depth.

• Soil profile described by Melissa Cann (May 2007)