Site MP18

Location: Yaapeet

Australian Soil Classification:
Northcote Factual Key: Gc 1.22

General Landscape Description: Upper slope of an east-west undulating dune.

MP18 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-15 cm	Yellowish brown (10YR5/4); loamy sand; loose surface condition; massive in structure; firm consistence dry; contains very few (<2%) soft carbonates; pH 8.4:	MP18 Profile
A2	15-30 cm	Brownish yellow (10YR6/6d) conspicuous bleach; loamy sand; massive in structure; firm consistence dry; contains very few (<2%) soft carbonates in patches (2 mm wide); pH 9.0; sharp and wavy change to:
Subsoil
B1	30-50 cm	Reddish yellow (7.5YR6/6); light sandy clay loam (becomes sandy clay loam with depth); massive in structure with a hard bleached capping; firm consistence dry; contains a few (10%) soft carbonates; pH 8.8:
B21k	50-80 cm	Reddish yellow (7.5YR6/6) with red (2.5YR5/8) mottles; light clay (sandy); weak medium subangular blocky structure (rough faced peds); strong consistence dry; contains many (20-50%) peds with a soft carbonate coating, in large patches (2-5 cm wide); pH 8.9:
B22k	80-130 cm	Reddish yellow (7.5YR6/6); sandy light clay; moderate medium subangular blocky, breaking down to fine subangular blocky structure with depth; strong consistence dry; contains many (30%) soft carbonates in patches and a few (10%) ped faces have dark flecking; pH 9.1:
B23	130+ cm	Yellowish red (5YR5/8); sandy clay loam (clayey); massive in structure; contains very few (<2%) carbonates; pH 9.5.

Key Profile Features:

High fine (58%) and coarse (35%) sand in the surface layers.
Quite an alkaline profile.
High accumulation of carbonate in the deeper subsoil.

Soil Profile Characteristics:

The surface is moderately alkaline. The upper subsoil is strongly alkaline and the deeper subsoil very strongly alkaline at 1m.	The majority of the soil profile is non-sodic, only becoming sodic at 120 cm.
The salinity rating is very low to low throughout the whole profile.	The clay content increases gradually with depth.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl₂)	EC 1:5	NaCI %	Exchangeable Cations				Field Capacity pF 2.5	Wilting Point pF 4.2	Coarse Sand (0.2 - 2 mm)	Fine Sand (0.02 -0.2 mm)	Silt (0.002 -0.02 mm)	Clay (<0.002 mm)
						Ca	Mg	K	Na
						meq/100g
A1	0-15	8.4	7.7	0.06		2.7	0.7	0.4	<0.1	3.8	18	58	35	0	6
A2	15-30	9	8.3	0.06		2.6	0.6	0.3	<0.1	3.6	2	57	36	0	6
B1	30-50	8.8	8.1	0.1		6.7	2	0.8	<0.1	14	16.7	42	37	0	18
B21	50-80	8.9	8.1	0.11		8.5	6.3	1.6	0.1	23.8	12.1	29	27	0
B22	80-130	9.1	8.3	0.13		4.2	6.6	1.4	0.1
B23	130+	9.5	8.6	0.18		2.3	6.2	1.4	1

Management Considerations:

Whole Profile

Plant available water capacity (PAWC)...........(quite a sandy profile).
Nabil Badawy suggests planting calcium carbonate tolerant species only, due to the occurrence of carbonate in the surface and subsoil.

Surface (A) Horizons

Both the surface soils have a very high sand (93%) content. The levels of organic carbon measured at the pit site is 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, erosion risk and low inherent fertility of the surface soil.
The low wilting point values (ie. 1.8 % and 2 %) of the surface horizons indicate that plants will be able to utilise very light rains when the soil is dry. However, due to the low water storage capacity, plants will soon suffer moisture stress unless further rainfalls occur.
Infiltration of water will be rapid in the surface soil and water will rapidly move down towards the subsoil. The presence of a conspicuous bleach is a symptom of the hard sandy capping on the massive subsoil. This occurrence indicates that the A2 horizon is periodically waterlogged and would be ‘soupy’, as water sat on top of the more slowly permeable subsoil. Deep ripping would allow this water to enter the subsoil and thus not be lost to evaporation.

Subsoil (B) Horizons

The subsoil has a moderate inherent fertility throughout which is beneficial for plant growth.
The strongly alkaline profile suggests that some nutrients (e.g. manganese, zinc, iron, copper) may be poorly available to plants.
The upper subsoil is non-sodic, however the calcium to magnesium ratio is 0.7 at 80 cm (decreasing with depth) and the soil disperses slightly after remoulding. This coupled with the sandy hard capping, is likely to restrict root and water movement somewhat.
B21 free lime content 1.7 %.

Notes

The paddock was cleared around 1915.
The landholder prefers extra legume crops with his grain and pasture rotations which help combat broem brass and increases fertility.
Peas were the crop in place during time of sampling and MRS were trialing grain legumes with fertilisers.

Profile Described By:
Profile described by Nabil Badaway, Mark Imhof and Sonia Thompson (12/10/94)

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