GP83

Site GP83 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-15 cm	Dark brown (10YR3/3); loamy sand; pH 4.9; clear change to:	Site GP83 Profile
A2	15-30 cm	Light yellowish brown (10YR6/4) conspicuously bleached (10YR8/1 dry) mottles; sand; pH 5.1; sharp change to:
Subsoil
B21	30-60 cm	Yellowish brown (10YR5/6) with brownish yellow (10YR6/8) and greyish brown (10YR5/2) mottles; medium heavy clay; strong very coarse columnar, parting to weak-moderate very coarse blocky and weak coarse polyhedral structure; strong consistence (dry); pH 6.3; gradual change to:
B22	60-100 cm	Brownish yellow (10YR6/6, 6/8); light medium clay (sandy); strong very coarse prismatic structure; isolated rounded quartz gravel (5 cm); isolated slickensides; pH 7.0; gradual change to:
B23	100-120+ cm	Yellowish brown (10YR5/6); medium clay (sandy); moderate coarse prismatic, parting to moderate coarse blocky structure; dark staining evident; contains few (10%) quartz grit; pH 7.3.

• Strong texture contrast between sandy surface (A) horizons and clayey subsoil (B21) horizon.
• Conspicuously bleached subsurface (A2) horizon.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC 1:5	Exchangeable Aluminium mg/kg	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
A1	0-15	4.9	4.3	0.08	26	1.5	0.41	0.07	0.28
A2	15-30	5.1	4.5	<0.05	13	0.35	0.10	<0.05	0.21
B21	30-60	6.3	5.2	0.11	12	2.1	6.1	0.14	1.7
B22	60-100	7.0	6.1	0.16		0.98	7.3	0.13	2.6
B23	100-120+	7.3	6.7	0.58		0.7	7.3	0.1	3.7

Horizon	Horizon Depth (cm)	Exchangeable Acidity meq/100g	Field Capacity 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)	Bulk Density Kg/L
A1	0-15	7.7	11	4	50	32	9	4
A2	15-30	1.1	7	1	50	37	8	2	1.5
B21	30-60	7.4	29	18	23	18	8	50	1.6
B22	60-100		28		24	21	9	48
B23	100-120+		17	15	9	30	18	42

• The sandy surface horizons have a low water storage capacity. The low wilting point values indicate that plants will be able to utilise light rains falling on relatively dry soils. However, due to the low water storage capacity, plants will soon suffer moisture stress unless further rainfall occurs. Organic matter is important in these sandy soils to enhance water holding capacity – as well as to enhance aggregation as well as fertility. These sandy soils have a low inherent fertility and are very strongly acid. Such strongly leached soils are also likely to be naturally deficient in nitrogen, phosphorus, sulphur and potassium. Lime application will result in increased pH levels and make certain nutrients such as phosphorus more available to plants. Deficiencies of the trace element molybdenum (Mo) are also likely to occur in acid sandy soils (soil adsorption of MO increases as pH decreases, leading to reduced availability to plants).

• The dense and coarsely structured upper subsoil is sodic and strongly dispersive. This will result in restricted root and water movement into the subsoil. After heavy rains water is likely to build up on top of the subsoil – leading to potential waterlogging in the sandy surface horizons.