GP57

GP57-GP60 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-25 cm	Dark brown (7.5YR3/3); fine sandy clay loam; moderate to strong coarse polyhedral, parting to strong fine polyhedral structure; weak to firm consistence dry; basalt fragments common (15-20%); pH 5.4	GP57 Profile
Subsoil
B1	25-40 cm	Reddish brown (5YR4/4); light clay; strong medium polyhedral, parting to fine structure; weak to firm consistence dry; contains many (40-50%) basalt fragments (2-10 cm in size); pH 6.1
B21	40-65 cm	Yellowish red (5YR4/6); medium heavy clay; strong medium polyhedral, parting to fine polyhedral structure; pH 6.1
B22	65-110 cm	Pale red (2.5YR7/4) with yellowish red (5YR5/8) mottles; medium clay; moderate polyhedral, parting to fine lenticular structure; contains kaolinitic material; pH 5.0
BC	110+ cm	Light Grey (N7) with dusky red (2.5YR4/4) mottles

Key Profile Features:

• Contains large amounts of basalt within the surface (A1) and subsurface (B1) horizons.
• Vertic properties present within the subsoil i.e. lenticular structure.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly Acid	Low-Moderate	Non-Sodic	None
Subsoil (B21 horizon)	Slightly Acid	Very Low	Non-Sodic	None1
Deeper subsoil (at 90 cm)	Strongly Acid	Very Low	Non-Sodic	None

The surface horizon is strongly acid. The subsoil is slightly acid becoming strongly acid with depth.

The salinity rating in the surface soil is low to moderate. The subsoil is very low.

The exchangeable aluminium levels in the surface are low. At 55 cm depth the levels increase and become very high at depth.

The clay content increases markedly at the A/B boundary.

Horizon	Horizon Depth	pH (water)	pH CaCl2	EC 1:5	NaCl	Exchangeable Cations
						Ca	Mg	K	Na
						Meq/100g
A1	0-25	5.4	4.9	0.25	<0.03	11	3.7	1	0.3
B1	25-40	6.1	5.2	0.07		5.8	3.9	0.4	0.48
B21	40-65	6.1	5.3	0.1		4.6	6.1	0.29	0.76
B22	65-110	5	4.3	0.11		0.92	3.8	0.1	0.59

Management Considerations:

Surface (A) Horizon

• The surface (A1) horizon is strongly acid. Levels of exchangeable aluminium measured are not high (i.e. 25 mg/kg). A pH/aluminium test sampled across the paddock would be appropriate to determine whether lime is needed to raise soil pH. However, other factors need to be considered before lime is recommended (e.g. pasture species grown, method of application, local trial responses, soil surface structure and likely cost/benefit).
• The inherent fertility of the surface (A1) horizon (based on the sum of the exchangeable calcium, magnesium and potassium cations) is moderate. The very high levels of organic matter at this site are important for improving soil fertility, water holding capacity and enhancing surface soil structure. The nitrogen levels are also very high. Planting legumes may help to alleviate the low fertility deficiency.
• The level of soluble salts in the surface is low to moderate and may restrict the growth of salt sensitive species (e.g. faba beans, linseed, chick peas and lupins). Roots for the current plant species were observed to 60 cm depth.

• The subsoil has a moderate inherent fertility throughout (based on the sum of the exchangeable basic cations).
• The presence of mottling throughout the subsoil indicates that the profile is seasonally waterlogged.
• The subsoil has vertic properties i.e. lenticular structure which indicates that significant shrinking and swelling occurs during wetting-drying cycles. This can disrupt the roots of perennial plants and will have implications for engineering applications (e.g. building foundations and fence lines).
• Contains a common (40-50%) amount of basalt only within the upper subsoil...............
• At 65 cm depth the soil becomes strongly acid and the exchangeable aluminium levels very high at 220 mg/kg. However, only deep rooted plants would be effected.