Dairy Soils in South-Western Victoria

The dairying areas of Victoria contain a large range of soil types. This wide range of soil types is the result of the distant past history of the area, weathering patterns, and agricultural influences. Knowing the local soil types helps farmers to better understand the peculiarities and limiting factors of their own soils. The different soil types have a range of different characteristics (for example, soil fertility, structure, acidity) that can impact on management and fertiliser decisions.


Dermosols

Dermosols are non-texture contrast soils, that have moderately deep and well structured subsoils.

Black Dermosol

Nature and Distribution Black Dermosols have mainly developed on marl, volcanic ash and scoria deposits, and can be associated with some stony rise landscapes. Management considerations These soils are relatively well drained due to the gradational soil profile and well developed structure. This allows more effective drainage compared to texture contrast soils. Black Dermosols associated with scoria are friable and very well structured. They are also high in clay and as a result can be prone to compaction. Some tend to be relatively high in free iron oxide which can result in P being tightly bound.

Photo of a Black Dermosol in a Soil Pit SW 26

Red Dermosol (Jancourt)

Nature and Distribution Small areas of red Dermosols occur on Port Campbell Limestone near Jancourt. Management considerations These gradational soils are reasonably well drained and have a relatively high nutrient status. Their relatively high clay content in surface horizons means that they can be prone to compaction.

Photo of a Red Dermosol in a Soil Pit called GP18 at Jancourt

Grey Dermosol (Cowleys Creek)

Nature and Distribution Yellow and Grey Dermosols (which tend to be calcareous at depth) occur on rises and plains associated with Gellibrand Marl deposits in the south-western parts of the region. (Cowleys Creek) Management considerations Pugging is likely on poorer drained lower slopes and plains. The Gellibrand Marl material is usually clay loams through to heavy clays (Figure 5.8). Chemically, these soils are much better than the lighter-textured Hanson Plains Sands material, but they do have some major physical problems. Chemically, they are deficient in nitrogen, phosphorus, potassium, sulphur and sometimes trace elements. These deficiencies can be corrected with routine fertiliser applications. The Gellibrand Marl soils are not as acidic as the lighter-textured Hanson Plains Sands soils, but they still usually benefit from lime application. Nutrients don't leach as readily from these soils as they do from the lighter-textured soils, and the Gellibrand Marl soils have a higher cation exchange capacity. The major physical limitation of these soils is their severe winter waterlogging. These soils have low hydraulic conductivity with heavier clay B horizons, which leads to perched watertables that reach or come close to the soil surface in winter. These perched watertables usually result in major pugging to pastures grazed by cattle in winter. This winter pugging seriously reduces the growth rates and utilisation of the pasture, degrades the pasture composition, and damages the soil structure. These clay soils are naturally dense and poorly structured. This is then made far worse by the regular heavy pugging damage on heavily stocked winter-wet farms. The full impact of this poor structure and high bulk density on such factors as root growth, pasture yield and pasture productivity has not yet been determined.

Photo of a Grey Dermosol at Soil Pit SW52 near Cowleys Creek

Acidic, Dystrophic Grey Dermosol on Hanson Plain Sand near Simpson

Nature and Distribution Grey (Bleached) Dermosols occur on sedimentary plains (Hanson Plain Sand) in areas around Simpson. Management considerations These soils are relatively sandy, strongly acidic and nutrient-poor. Exchangeable Aluminium can be high and liming may be required. Being low in fertility these soils respond well to fertiliser. Some trace element deficiencies likely.

Photo of a Grey Demosol at Soil Pit SW21 taken near Simpson

Brown Dermosol

Nature and Distribution Acidic, Brown Dermosols are common on many of the steep slopes of the Cretaceous sediments associated with the rolling to steep hills of the Otway Ranges. Management considerations Well-structured Dermosols generally support high pasture production with adequate fertiliser. They have moderate fertility and water holding capacity and are generally well drained. Tend to be strongly acidic so can be issues with aluminium toxicity. In higher rainfall areas these soils can be strongly acid throughout and exchangeable Aluminium can be high - liming may be required. Areas of lower fertility also occur - respond well to fertiliser.

Photo of a Brown Dermosol near Weeaproinah

Sodosols

Sodosols are characterised by a strong texture contrast between the surface and subsoil horizons and the coarsely structured subsoil is often dense and sodic. Subsoils are not strongly acid (i.e. pH >5.5 in water) but are sodic. Surface texture ranges from sandy loam to clay loam over medium to heavy clay


Sodosols

Sodosols are common on basalt plains and rises throughout much of the region. They are also common on sedimentary plains and rises south of the Princes Highway in lower rainfall areas

Nature and Distribution The subsoils of Sodosols in the region also often display a strong shrinking and swelling characteristic (i.e. vertic) and the subsurface horizons can contain significant amounts of ferruginous nodules, often referred to as ‘buckshot’ (i.e. ferric). The sodic subsoils often disperse and are usually dense and coarsely structured. This results in restricted root and water movement into the subsoil. Waterlogging can be common in wetter periods and subsoil drainage is poor. In basalt areas, the subsoil horizons can become calcareous at depth. Surface soil structure is often weak and pugging can be an issue in winter and spring. Bleached subsurface horizons often become “spewy” and tractor bogging potential can be high in winter. Management considerations Limited cultivation options exist where structure is coarse and dense. Due to the plastic and sodic nature of the soil – agronomic practices (such as tillage) can cause severe subsurface and subsoil structure deterioration. Where deeper, surface horizons provide enhanced rooting environment. Lighter-textured (i.e. sandy) surface soils allow plants to respond to lower rainfall events.

Kurosols

Kurosols have clay subsoils which are strongly acid (i.e. pH <5.5 in water). Their surface texture ranges from loam to fine sandy loam over a clay subsoil.

Benefits Subsoils are usually better structured and drained than Sodosols. Vertosols often have self-mulching surfaces, although more coarsely structured surface soils also occur. Subsoils are often sodic and can be calcareous at depth, often with visible free lime. Constraints Strongly acid subsoils (pH less than 5.5 in the lower horizons).

Vertosols

Vertosols are clay soils that display significant shrinking and swelling during wetting and drying cycles i.e. display vertic characteristics. They exhibit strong cracking when dry and at depth have slickensides and/or lenticular peds. Due to the strongly vertic nature of these soils, gilgai ('crabholey') microrelief is common.

Benefits Vertosols are reasonably common throughout the region on basalt plains and rises as well as on some alluvial plains, swamps and lunettes. Constraints Vertosols often have self-mulching surfaces, although more coarsely structured surface soils also occur. Subsoils are often sodic and can be calcareous at depth, often with visible free lime.

Hydrosols

Hydrosols are......

Benefits Many of the soils in valley floors and other low-lying areas are Hydrosols which tend to be saturated for a number of months in most years. These have not been mapped out separately in south-west Victoria but will be common in many areas where conditions exist – but as they are not extensive it is difficult to map them out separately. Constraints These soils are waterlogged for at least three months of the year in most years. Pugging is also an issue in winter and spring. In drier conditions they may provide subsoil moisture availability which can be important for deeper rooted plants.

Chromosols

Chromosols have a strong texture contrast between the loamy surface (A) horizons and the clayey upper subsoil (B) horizons. The subsoil is also not strongly acid i.e. pH of greater than 5.4 (water) and not sodic.

Benefits Chromosols are common on sedimentary plains and rises in southern parts of the Corangamite region (e.g. south-east and south-west of Colac). Chromosols are also widespread on basalt and volcanic ash/scoria deposits (where they often have darker coloured subsoils, i.e. black or brown). Constraints Strong texture contrast provides a moderate restriction to deep drainage. Subsoils, however, are generally better structured and drained, compared to Sodosols. Subsoils are not strongly acid in upper subsoil (compared to Kurosols)

Podosols

Podosols are mainly sandy soils with accumulations of organic materials and aluminium (with or without iron compounds) in subsoil horizons – often referred to as “coffee rock”.

Podosols Occur along parts of the coastline, siliceous sands have been deposited by wind during the Holocene period. Benefits Well drained where impermeable layer (‘coffee rock’) is deeper – good wintering i.e. minimal pugging; Good autumn and winter pasture growth In their original state, these soils usually only supported heathland or grasstree plain vegetation. They are strongly to very strongly acidic and liming is essential for pasture establishment. They are also deficient in many major nutrients, including N, P, K as well as trace elements such as molybdenum, copper and zinc. Being sandy these soils have a relatively low water-holding capacity. Drought stress in summer can be a problem and affect pasture persistence. However, the low wilting point of the sandy surface horizons means that plants can better access low rainfall events. Sandy soil such as these are usually well drained – unless they occur in lower lying parts of the landscape. Sometimes though they can have an underlying layer of relatively impervious 'coffee rock' or a clay subsoil (B horizon), which can result in a perched watertable and lead to winter waterlogging problems, if this occurs reasonably close to the surface. Constraints Light textured soil resulting in high nutrient leaching; Trace element deficiencies common; Low water holding capacity; Dries out fast with the onset of warm weather - prone to summer drought stress; Need irrigation to grow summer crops; Strongly acid with high exchangeable Al – liming required

Shallow, stony soils Very shallow and stony Dermosols (which can be black, red or brown) occur on the stony rises surrounding Lake Corangamite and to the north and south of Derrinallum. Weakly developed Rudosols also occur on rock. Benefits These soils are generally friable earths but are usually shallow and stony. Stoniness and waterlogging are restrictions to productivity.

Brown Kandosol near Simpson Constraints Strongly acid upper soil profile.

Photo of a Brown Kandosol at Soil Pit SW24 near Simpson