MP20

	Australian Soil Classification: Endohypersodic, Regolithic, Hypercalcic CALCAROSOL
Location: Pirlta	General Landscape Description: Crest of east-west dune.

Soil Profile Morphology:

Surface Soil

A11	0-15 cm	Reddish brown (5YR4/4); light sandy loam; hardsetting surface crust up to 1 cm thick; massive in structure; slightly calcareous; pH 8.9; sharp change to:	MP20 profile
A12	15-50 cm	Dark reddish brown (5YR3/4); light fine sandy loam; massive in structure; slightly calcareous; pH 8.9; clear change to:
Subsoil
B1	50-60 cm	Yellowish red (5YR4/6); fine sandy loam; massive in structure with hard capping; slightly calcareous; pH 9.0; gradual change to:
B21k	60-90 cm	Yellowish red (5YR4/6); fine sandy loam; weak coarse angular blocky structure; soft carbonate common (15%); pH 9.2; gradual change to:
B22	90-110 cm	Yellowish red (5YR5/6); sandy loam; weak coarse angular blocky structure; contains a few (5%) soft carbonates; pH 10.0; gradual change to:
B23k	110-150 cm	Yellowish red (5YR5/6); fine sandy clay loam; weak structure; contains very many (>50%) soft carbonates; pH 10.1.

Key Profile Features:

Soil Profile Characteristics:

The surface soil is strongly alkaline.
The upper subsoil is very strongly alkaline
becoming extremely alkaline at about 80 cm.

The salinity rating for the surface and
upper subsoil is low, becoming moderate at 1m.

The surface and upper subsoil is non-sodic.
At about 90 cm the deeper subsoil becomes strongly sodic.

Management Considerations
Whole Profile

The strongly alkaline profile suggests that some nutrients (e.g. manganese, zinc, iron, copper) may be poorly available to plants. Nutrient deficiencies can be assessed by plant tissue analysis. Plant species should be chosen in accordance with this pH level.
The profile is very sandy throughout and at 50-90 cm (B21) the subsoil has a very high fine sand content (66%). Accordingly, the water holding capacity is very low throughout.

Surface (A) Horizon

The surface soil has a very high fine sand content and is hardsetting when dry. When cultivated in a dry condition it will become ‘powdery’ and subsequent rainfall may result in surface sealing occurring. The levels of organic carbon measured at the pit site are quite low (this may or may not be representative of the whole paddock). Organic matter levels will decline if cropping takes place and can be improved by adopting practices such as residue retention, minimum tillage and utilising pasture rotations. Increased organic matter will both improve aggregation as well as assist in the low water holding capacity and low inherent fertility of this surface soil.
The levels of total nitrogen measured at this pit site is quite low. However, this is best assessed by taking a bulked sample from across the paddock.
The low wilting point values (ranging from 2.9 to 2.4) throughout the surface soil indicate that plants will be able to utilise light rains during dry periods, by taking water up immediately. However, due to this soils low water storage capacity, plants will suffer moisture stress unless further rains occur.
Infiltration of water is likely to be high in the surface horizons and interestingly, the majority of roots are in the upper surface (0-15 cm).
There would be very high evaporation from these surface horizons as they have very sandy textures and water would evaporate just as quickly as if the water was sitting on the upper surface.

Subsoil (B) Horizon

The salinity rating becomes moderate at about 1 m depth. These levels of soluble salts are likely to restrict the growth of salt sensitive plant species (e.g. faba beans, linseed, chickpeas and lupins) especially those that are deep rooted.
The subsoil has a moderate inherent fertility throughout the subsoil which is beneficial for plant growth.
The subsoil becomes strongly sodic at 90 cm depth but the majority of root growth occurs above this area.

Comments:

At time of soil sampling (October 1994) the site had not been cropped for 6 years, but grew good wheat crops before that time.

Profile described by: Mark Imhof and Sonia Thompson (October 1994)

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