SW79

SW79 Landscape

Soil Profile Morphology:

Surface Soil

Ap	0-20 cm	Very dark brown (10YR2/2 moist), grey (10YR5/1 dry); fine sandy loam; pH 5.1; clear change to:	SW79 Profile
A21e	20-40 cm	Greyish brown (10YR5/2 moist), conspicuously bleached (10YR7/1 dry); fine sandy loam; pH 6.4; clear change to:
A22ec	40-50 cm	Greyish brown (10YR5/2 moist), very pale brown (10YR8/2 dry); fine sandy loam; abundant rounded ironstone gravel (5-20 mm), minor fine quartz (8-20 mm); sharp change to:
Subsoil
B2t	50-90/110 cm	Very dark greyish brown (10YR3/2 moist) with few, fine [up to 20 mm], red mottles on ped interiors; medium heavy clay; strongly pedal, coarse to medium (40-60 mm) prismatic, parting to coarse (30-40 mm) blocky structure (with some fine lenticular peds); sandier matrix as horizon deepens; pH 6.6; abrupt to clear and irregular change to:
C	110 cm+	Yellow and grey mottled cemented sand with thick dark clay infills in cracks; infills can be quite thick (3 mm) and take form of vertical lenticular clay peds; pH 6.

• Strong texture contrast between surface (A) horizons and subsoil (B21) horizons.
• Large amount of iron stone gravel ("buckshot") in deeper subsurface (A22) horizon.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly Acid	Medium	Non-Sodic	None
Subsoil (B21 horizon)	Slightly Acid	Very Low	Marginally Sodic	None

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC 1:5	NaCl %	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
Ap	0-10	5.1	4.5	0.32	0.03	3.5	0.8	0.7	<0.1
A2	25-40	6.4	5.4	<0.05		0.99	0.9	0.07	0.17
B2	60-80	6.6	6.1	0.05		4.4	8.5	0.19	1.5
C	130+	6.8	6	0.11	0.02

Horizon	Horizon Depth (cm)	Ex Al mg/kg	Ex Ac meq/100g	Field pF2.5	Wilting Point pF4.2	Coarse Sand (0.2- 2.0 mm)	Fine Sand (0.02- 0.2 mm)	Silt (0.002- 0.02 mm)	Clay (<0.002 mm)
Ap	0-10	24	16	26.2	10.9	21.1	45.4	15	8
A2	25-40	<10	4.4	15	3.5	19.4	54.1	16.5	10
B2	60-80		12	42.3	30.1	2.6	7.6	3.5	85
C	130+

Management Considerations:

Subsoil (B) Horizons

• The subsoil displays vertic features (i.e. slickensides) which indicates that significant shrinking and swelling occurs during wetting and drying cycles. This may have engineering implications and is likely to explain the variability in surface horizon depth across the trench.

• As the B horizon approaches C horizon peds gradually become sandier in the matrix until subsoil takes on the appearance of a fractured sandstone with thick clay coatings infilling in the cracks. These in places are quite thick (~3 mm) and take on form of vertical lenticular peds.
• Soil approx. 1 m over weathered sandstone probably Tpb but mapped as Tmi on 1:50 000 Beech Forest geology sheet. Boundary to B horizon becomes extremely wavy (30-80 cm depth) as unit continues down slope. Abundant gravel in A2, 100 to 400 mm thickness.