MM112

Site code
      MM112
Location
      Colac (Larpent Road), Colac district, south-west Victoria
Landform
      Alluvial plain
Geology
      Quaternary alluvium: paludal lagoon and swamp deposits; silt, clay
Element
      Lower slope

Profile morphology
Horizon

Depth (cm)

Description

A1
0–30
Very dark brown (10YR2/2); fine sandy loam; apedal massive structure; weak consistence (dry); clear boundary to:

A2
30–60
Sporadically bleached, light grey (10YR7/2 dry); fine sandy loam; weak consistence (dry); sharp boundary to:

B21
60+
Black (10YR2/1) with grey (10YR4/6) mottles; heavy clay; strong coarse blocky structure; strong consistence (dy).


ASC: Eutrophic; Mottled-Subnatric; Black Sodosol

Analytical data Source: Government of Victoria, State Chemistry Laboratory.

Site MM112
Sample
depth
pH
EC
NaCl
Ex Ca
Ex Mg
Ex K
Ex Na
Ex Al
Ex acidity
Horizon
cm
H2O
CaCl2
dS/m
%
cmolc/kg
cmolc/kg
cmolc/kg
cmolc/kg
mg/kg
cmolc/kg
A1
0–30
5.6
N/R
0.05
N/R
3.2
3.2
0.3
0.3
N/R
10.6
A2
30–60
5.8
N/R
0.04
N/R
1
1
0
0.2
N/R
4.4
B21
60+
6.4
N/R
0.17
0.04
4.8
4.8
0.3
2.8
N/R
13.9

Site MM112
Sample
depth
FC
(-10kPa)
PWP
(-1500kPa)
KS
FS
Z
C
Org C
Bulk density
Horizon
cm
%
%
%
%
%
%
%
t m-3
A1
0–30
25.7
14.1
21
47
17
13
2.4
1.14
A2
30–60
N/R
N/R
26
51
15
8
0.6
N/R
B21
60+
44.8
31.7
10
23
7
58
N/R
0.94

Management considerations
These soils have sandy topsoils and exhibit a strong texture contrast between the surface soil and the subsoil with a bleached A2 horizon. The sandy topsoils have poor plant water holding capacity and poor nutrient holding capacity and due to the low level of bonding between soil particles are prone to wind, sheet and rill erosion (depending on organic matter content and vegetative cover). The bleached A2 horizons are an indication of restricted drainage, poor soil structure (often massive) and low organic matter and nutrients.

These soils are associated with sodic subsoils having poor structure. The poor structure results in dispersion and subsequent clogging of pores restricting water and gas movement through the subsoil. Mottled subsoils are common and are a further indication of periodic waterlogging and restricted water movement.

Maintenance of a vegetative cover is important to improve topsoil stability. Options include reduced tillage, improving organic matter content and altering the subsoil through artificial drainage (ripping, mole drainage) and/or chemical amelioration (gypsum) to improve structure.
CC BY 3.0 AU

This page contains material sourced from the Victorian Resources Online (VRO) website, originally published by the State Government of Victoria. The content is licensed under the Creative Commons Attribution 3.0 Australia licence . The material has been adapted and re-formatted; no endorsement by the Victorian Government is implied.