Marong map unit Qbg

Back to: A Land Capability Study of the Rural City of Marong

Map Unit:	Quaternary basalt, drainage depression	Map Unit Symbol:	Qbg
		% of Study Area:	0.2

Land-form diagram for marong map unit Qbg

General Description:
The wetter areas of the basalt plain form swampy depressions. As with all drainage units, the associated soils are variable. They are typically yellow duplex with silty loam top soils, bleached A2 horizons and heavy, mottled clay subsoils. Minor soil variations include absent A2 horizons and whole-coloured subsoils on the edge of depressions where drainage is slightly better, and self-mulching grey uniform clays In shallower depressions. In very slight-depressions, between rock outcrops, the soils are similar to those on the very gentle slopes.

Site characteristics:

Parent material age:	Quaternary	Depth seasonal watertable:	0 m
Lithology:	Basalt	Potential recharge to groundwater:	Low
Landform Pattern:	Lava plain	Flooding risk:	High
Element:	Swamp	Drainage:	Very poorly drained
Slope common:	1 %	Depth to hardrock:	1.1 m
Slope range:	0 - 3 %
Rock outcrop:	2 - 10 %

Major vegetation: Red Gum, Yellow Box, Grey Box, Buloke, Sea Barley Grass, Spiny Rush, Wallaby Grass

Present land use: Native forest (partially cleared), grazing and native pasture

Land degradation:	Water erosion		Wind erosion	Salting	Acidification
Land degradation:	Sheet/rill	Gully	Wind erosion	Salting	Acidification
Susceptibility	Low	Moderate	Very Low	High	Moderate
Incidence	Low	Low	Very Low	Moderate	Low

Soil profile characteristics:

Permeability (measured - average, range):	N.A.
Permeability (estimated):	Very slow
Available water capacity:	151 mm H₂O
Linear shrinkage (B horizon):	14 %

Soil profile description:

A1	0-12 cm	Brownish grey (10YR5/1) silty loam, moderate structure, angular blocky pads 10-20 mm, smooth fabric, moderately weak consistence, pH 6.9. Clear transition to
A2	12-27 cm	Greyish yellow brown (10YR6/2) fine sandy loam, bleached (10YR8/2) when dry, weak structure, subangular blocky peds 10-20 mm, rough fabric, moderately firm consistence, pH 6.1. Abrupt transition to
B21	27-52 cm	Greyish yellow brown (10YR5/2) heavy clay, many distinct orange mottles, moderate structure, subangular blocky pads 10-20 mm, smooth fabric, moderately firm consistence, pH 5.4. Clear transition to
B22	52-73 cm	Dull yellowish brown (10YR5/4) heavy clay containing wind blown quartz particles, many distinct dark brown mottles, weak structure, subangular blocky peds 10-20 mm, smooth fabric, moderately firm consistence, pH 5.7. Clear transition to
B23	73-90 cm	Dull yellowish brown (10YR5/4) medium heavy clay, many distinct pale brown mottles, moderate structure, angular blocky pads 10-20 mm, smooth fabric, moderately weak consistence, less than 2% basalt fragments and carbonate nodules, pH 6.9. Clear transition to
B24	90-107 cm	Pale grey/brown (2.5YR6/2) medium heavy clay, common distinct yellow mottles, strong structure, subangular blocky peds less than 2 mm, smooth fabric, moderately weak consistence, abundant basalt fragments and carbonate nodules, pH 7.4
C	107 cm	Rock

Soil classification:

Factual Key (Northcote):	Dy 3.42 (major) Dy 3.14, Uf 6.31/3 (minor)
Australian Soil Classification:	Bleached, Kurosolic, Redoxic, Hydrosol; deep, medium, silty, non-gravelly
Unified Soil Group:	CH

Interpretation of soil analyses*

Horizon	pH	Gravel %	E.C. (salts)	Nutrient Status	P	K	Al	Organic Matter	Dispersibility
A1	6.9	0.7	VL	M	S	S	S	H	L
A2	6.1	5.8	VL	VL	D	S	S	L	H
B21	5.4**	0.9	VL	M	D	S	T	L	H
B22	5.7	0.4	VL	M	D	S	S	L	H
B23	6.9	2.4	VL	H	D	S	S	L	H
B24	7.4	43.0	L	VH	D	S	S	L	H

VL : Very Low; L : Low; M : Moderate; H : High; VH : Very High; D : Deficient; S : Satisfactory; T : Toxic; **: Acid * See Appendix 4 for analytical results

Land capability assessment

Land Use	Class	Major limiting feature(s)/ landuse
Agriculture (CTS values)	C₃T₂S₅	High seasonal watertable
Effluent disposal (septic tanks)	5	High seasonal watertable, very poor drainage, high risk of flooding, very slow permeability
Farm dams (earthen)	5	High seasonal watertable
Building foundations - slab	5	Very poor drainage, high seasonal watertable, high risk of flooding
Building foundations - stumps/footings	5	Very poor drainage, high seasonal watertable, high risk of flooding
Secondary roads	5	High risk of flooding, high seasonal watertable, very poor drainage
Urban residential	5	Secondary roads, building foundations
Rural residential	5	Farm dams, effluent disposal, secondary roads, building foundations

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