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Victoria

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Soil Texture

Victoria’s grain farms are predominantly located in western and northern Victoria, with the majority in the Mallee and Wimmera regions. Grain growing in Victoria is continuing to expand into the high rainfall zones of southern Victoria and to a lesser extent Gippsland, on land previously used exclusively for pasture production. Grain production in Victoria accounts for approximately 11 per cent of Australia’s production which has fluctuated over recent years primarily due to weather events. It peaked at 7.7 million tonnes in 2010-11 and recorded a low of 1.8 million tonnes in 2006-07. The Victorian Grain industry consists of three types of broadacre crops, cereals, oilseeds and pulses. Cereal (mainly wheat and barley) production represents 82 per cent of Victoria’s grain production, with wheat accounting for around 60 per cent of the total cereal crop. Since 1980, production of oilseeds and pulses has grown rapidly from 1 per cent to almost 20 per cent of total grain production.

There are three major soil groups in these grain cropping regions of the Mallee, Wimmera and the south western Victorian. Vertosols (cracking clay soils), Sodosols (soils with a strong texture contrast between surface and subsurface horizons and with subsoil horizons that are sodic) and Calcarosols (gradational textured soils with an abundance of lime in the profile). A fourth group, the Chromosols also are common in the high rainfall South-western Victorian region.

Vertosols are often called cracking clay soils. They have a clay texture (>35% clay) throughout the profile; display strong cracking when dry, and shrink and swell considerably during wetting and drying phases. Based on colour of the upper 50 cm ofthe soil profile, they can be grouped into suborders. Grey Vertosols are the most common in the Wimmera, with minor occurrences of Red and Brown Vertosols. Self-mulching Vertosol soils are common in the Horsham and Kaniva regions.

Sodosols occur on a wide range of landforms (from gently undulating plains and rises to undulating low hills). Surface soil textures and depths vary considerably and have significant implications for management. Sodosols tend to be found mainly in the southern, eastern and western Wimmera with smaller areas in the northern Mallee and east of Birchip. Sodosols are also common on basalt plains and rises throughout much of south-western Victoria. They are also common on sedimentary plains and rises in lower rainfall areas. The subsoils of Sodosols in the region often display a strong shrinking and swelling characteristic i.e. vertic, and the subsurface horizons can be ferric i.e. contain significant amounts of ferruginous nodules ‘buckshot’.

Calcarosols do not have a strong texture contrast between surface and subsurface horizons and are calcareous throughout. They often contain calcium carbonate (lime) as soft or hard fragments. They are most common in the north-east of the region. Calcarosols (often called ‘mallee loams’, ‘mallee sands’ or ‘calcareous earths’) are soils formed on calcareous aeolian sediments of variable texture. Calcarosols vary quite considerably in terms of soil texture, ranging from those dominated by sands to those that are clayey throughout, and this has a big influence on the agronomic properties of the land. Three kinds of Calcarosols occur: light textured (sandy to loamy), heavy textured (clay loamy to clay) and stony.

Chromosols are most common in the Glenelg-Hopkins region of south western Victoria and can occur in many types of landscape. They are soils that have strong texture contrast between the surface (A) horizons and the clay subsoil (B) horizons. The subsoil is also not strongly acid i.e. pH is greater than 5.5 in water.