LP9

LP9 Landscape

Soil Profile Morphology

Surface Soil

A1	0-5 cm	Dark brown (10YR3/3) light fine sandy clay loam; weakly structured; firm consistence dry; contains occasional shale fragments; pH 5.5; sharp and irregular change to:	LP9 Profile
A2	5-10 cm	Light brown (7.5YR6/4) conspicuously bleached fine sandy clay loam; weakly structured; strong consistence dry; contains a slight (10%) amount of ferruginous nodules (buckshot); pH 6.5; sharp and irregular change to:
Subsoil
B21	10-25 cm	Yellowish Red (5YR5/8) heavy clay; moderate coarse columnar, breaking down to strong coarse blocky structure (with smooth faced peds); very strong consistence moist; contains occasional shale fragments; pH 7.1; sharp and wavy change to:
B22	25-40 cm	Red (2.5YR4/8) heavy clay; strong medium blocky structure; very strong consistence moist; contains occasional shale fragments; pH 8.6 :
B3k	40-100 cm	Strong brown (7.5YR4/6) medium clay; with a heavy (>50%) amount of soft carbonate together with weathered shale; pH 9.3; gradual change to:
C	100+ cm	Laminated soft shale.

• Strong textural contrast between A horizon and clay B horizons.
• Sodic subsoil.
• Increasing pH with depth down the profile.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	strongly acid	very low	non-sodic	water-stable
Subsoil (B21 horizon)	slightly alkaline	very low	sodic	strong
Deeper subsoil (at 1 m)	very strongly alkaline	low	strongly sodic	strong

Management Considerations:

Surface (A) horizons

• The surface horizon has high levels of organic carbon and total nitrogen and a moderate overall nutrient status. However, being very shallow (i.e. 5 cm deep) it provides a limited rooting environment above the sodic subsoil.
• The high organic matter levels ensure that the surface aggregates are water-stable and will not readily break down when wet.
• Aluminium and manganese toxicity can occur in strongly acid surface soils, although exchangeable aluminium and manganese levels appear relatively low at this site. A lime test (sampled at the paddock level) may be appropriate to determine whether lime is needed to raise the pH levels.
• The conspicuously bleached A2 horizon indicates that periodic waterlogging may occur. This horizon has low fertility and is likely to become "soupy" when worked in a wet condition (as is evident by strong dispersion occurring after remoulding).

• The coarsely structured and dense subsoil (i.e. B21 horizon) is sodic and becomes strongly sodic with increasing depth down the profile. Strong dispersion occurs as a result, creating conditions which will restrict water and plant root movement.
• Effective plant rooting depth is shallow due to the coarsely structured sodic subsoil being encountered at 10 cm depth. Plant available water capacity for the profile is also low as a consequence.
• At a depth of 40 cm the soil becomes strongly alkaline which may result in nutrients such as phosphorous, iron, manganese and zinc becoming poorly available to plants.