SW31

Grazing paddock (dairy)		Site Code	SW31	Bleached-Mottled, Mesotrophic, Brown KUROSOL Melacic-Bleached
		Location	Gerangamete
		Landform	Undulating to rolling plain
		Geology	Tertiary - Moorabool Viaduct Formation.
		Element	Crest, upperslope


Horizon	Depth (cm)	Description
A1	0-15	Greyish brown (10YR3/2); light fine sandy clay loam; weak coarse blocky structure; very firm consistence (moist); pH 4.8:
A21	15-30	Dark brown (7.5YR3/2); very fine sandy clay loam; weak coarse blocky structure; firm to very firm consistence moist; pH 4.8:
A22	30-40	Greyish brown (10YR5/2), conspicuously bleached; very fine sandy clay loam; very firm consistence (moist); pH 4.7:
A23	40-50	Greyish brown (10YR5/2) with brownish yellow (10YR6/6) mottles, conspicuously bleached; heavy very fine sandy clay loam; very firm consistence (moist); pH 4.7; abrupt and wavy boundary to:
B21	50-70	Brown (10YR5/3) with yellowish brown (10YR5/6) mottles; light medium clay; moderate medium prismatic, parting to strong coarse blocky structure; strong consistence (moist); pH 4.7:
B22	70+	Greyish brown (10YR5/2) with yellowish brown (10YR5/6) mottles; medium clay; moderate coarse prismatic, parting to moderate coarse blocky structure (with strong fine blocky structure in patches); strong consistence (moist); pH 4.8.


Management considerations
Strong texture contrast between the surface soil and the subsoil is a very important soil feature. This can have a major effect by reducing and/or redirecting the internal drainage and restricting root growth beyond the upper horizons. 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. Bleached A2 horizons (or subsurface soils) are a major feature of many of soils within the Corangamite CMA region. They are an indication of restricted drainage, poor soil structure (often massive) and low organic matter, nutrient and water holding capacity, nearly always in conjunction with a restrictive soil below such as a clayey soil or a pan (e.g. coffee rock). These bleached horizons may act as conduit for subsurface flow, particularly on sloping ground. If the soil is dispersive then gypsum application would be suitable, while increasing organic matter and maintaining vegetative cover is important. Acidic surface soils (topsoil) are often associated with sandy surfaces due the lack of base minerals and may or may not have organic matter (humose or peaty surfaces). Their acidic nature restricts the uptake of certain nutrients as well as intolerance for some plant species (due in part to the increasing mobilisation of aluminium and manganese). The application of lime is the main method of increasing the pH, reducing toxic levels of nutrients to plants while increasing the availability of nutrients such as calcium, potassium and molybdenum. Hardsetting surface and subsurface soils (A1 and A2) are another key feature of many of the texture contrast soils in the CMA. These soils usually have medium to heavy textures and may be sodic (and therefore dispersive), often with low liquid limits (change from solid, plastic to liquid quickly). Water (and gas) movement and root growth is restricted in this soil. Improvement of soil structure through increased organic matter would be useful, and addition of gypsum where sodic would be beneficial. Bringing this material to the surface is likely to contribute to surface sealing and increase erosion susceptibility. Mottled subsoils are common and are an indication of periodic waterlogging, particularly if the mottles are pale (low oxygen conditions). Some brighter mottling may be due to past soil mixing and clay alluviation. Improved drainage, with the application of gypsum for sodic subsoils may be beneficial. Acidic subsoils generally occur on acidic parent material or where there has been sufficient leaching of the soil. These subsoils affect nutrient availability, creating a nutrient imbalance and the potential for aluminium and manganese toxicity. Deficiencies of calcium, potassium and molybdenum are likely. Where the acidity is deep, acid tolerant plants are a practical option, while increasing the pH may be preferable by applying lime.

Analytical data

Site SW31	Sample depth	pH		EC	NaCl	Ex Ca	Ex Mg	Ex K	Ex Na	Ex Al	Ex acidity	FC (-10kPa)	PWP (-150kPa)	KS	FS	Z	C
Horizon	cm	H₂O	CaCl₂	dS/m	%	cmol_c/kg	cmol_c/kg	cmol_c/kg	cmol_c/kg	mg/kg	cmol_c/kg	%	%	%	%	%	%
A1	0-15	4.8	4.3	0.26	0.02	5.1	0.4	0.6	0.05	N/R	N/R	36	11.6	5	37	30	15
A21	15-30	4.8	4.4	0.38	0.04	5.9	0.6	0.3	0.05	N/R	N/R	35.9	11.2	4	38	30	15
A22	30-40	4.7	4.2	0.24	N/R	1.2	0.2	0.3	0.05	N/R	N/R	31.1	7.7	3	42	35	18
A23	40-50	4.7	4.1	0.14	N/R	0.8	0.7	0.3	0.05	N/R	N/R	25.3	9.2	3	40	33	24
B21	50-70	4.7	4.1	0.19	N/R	1.5	2.7	0.3	0.05	N/R	N/R	34.7	19.3	1	28	24	47
B22	70+	4.8	4.1	0.18	N/R	0.8	3.1	0.1	0.3	N/R	N/R	43.3	24.8	1	19	20	59

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