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MP30

Group: Birchip Cropping Demonstration Group Australian Soil Classification: Episodic-Epicalcareous, Epipedal, Yellow VERTOSOL
Northcote Factual Key: Ug 5.3Great Soil Group: brown clay
General Landscape Description: Flood plain within the Tyrell Creek Landsystem (Rowan and Downes, 1963).


Soil Profile Morphology:

Surface Soil

A10-20 cmStrong brown (7.5YR4/6); medium clay; surface cracking; very firm consistence dry; pH 8.0; clear change to:
MP30 profile
MP30 profile
Subsoil
B220-40 cmReddish yellow (7.5YR6/6); light medium clay; pH 9.6; clear change to:
B3140-60 cmPinkish grey (7.5YR7/4); light medium clay; contains a few (2-10%) manganese segregations:
B3260-110 cmLight brownish grey (10YR6/2); light clay; pH 9.2.

Key Profile Features:


Soil Profile Characteristics:

pH
Salinity
Sodicity
Dispersion
Surface
(A1 horizon)
moderately alkaline
low
sodic
moderate
Subsoil
(B21 horizon)
extremely alkaline
medium
very strongly sodic
complete
Deeper subsoil
(at 1 m)
very strongly alkaline
high
strongly sodic
strong

MP30 graphs

Horizon
Horizon Depth
(cm)
pH
(water)
pH
(CaCl2)
EC
1:5
NaCl
Total Nitrogen
%
Organic Carbon
%
Exchangeable Cations
Ca
Mg
K
Na
Meq/100g
A1
0-20
8
7.2
0.31
<0.05
9.8
6.9
1.5
3
B21
20-40
9.6
8.9
0.67
<0.05
5.6
8
1.3
14.7
B31
40-60
B32
60-110
9.2
8.7
1.16
<0.05
7.6
7.2
1.1
12.2



Horizon
Horizon Depth
(cm)
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)
A1
0-20
34.1
25.1
B21
20-40
50.7
36.3
B31
40-60
B32
60-110


Management Considerations

Surface (A) Horizon
  • The surface soil is sodic and disperses. It is likely to develop surface crusting if cultivated in a moist to wet condition or exposed to raindrop impact.
  • The high wilting point value (ie. 25%) indicates that plants will be unable to utilise light rains when the soil is relatively dry.
  • Tillage, trafficking or over-stocking should be avoided if the soil is wet (ie. wetter than the plastic limit). At such moisture conditions, these activities can result in structural damage (eg. compaction, smearing) occurring. Ideally, tillage should take place when the soil is drier than the plastic limit, down to at least the tillage depth.
  • The total nitrogen level measured at the pit site is quite low. Taking a bulked sample from across the paddock may be useful to determine whether nitrogen needs to be added.

Subsoil (B) Horizons
  • The top of the subsoil is extremely alkaline which may result in nutrients such as phosphorus, iron, manganese and zinc becoming poorly available to plants.
  • The subsoil is very strongly sodic and completely disperses in water. It is likely to seriously restrict water and root movement into the profile. Also, the very strongly sodic subsoil may create adverse chemical conditions for some plants.
  • The light grey coloured deeper subsoil suggests that this zone becomes saturated in wet periods which restricts aeration.
  • The level of soluble salts is medium in the upper subsoil (ie. 20-40 cm depth). This may affect the growth of salt sensitive species (eg. chick peas, lupins). The salinity rating becomes high in the deeper subsoil. It should be noted, however, that even though the electrical conductivity (EC) levels are high, the level of sodium chloride salts measured is low. This would suggest that either the sodium chloride analysis is wrong or that the majority of the salts are non sodium chloride. It is suggested that another salt test be done on the subsoil to confirm this.

Profile Described By: Mark Imhof and John Martin (23/1/93).
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