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Iconic Soils of NSW - Yellow Sodosol

The Yellow Sodosol is a widespread soil, occurring on many different parent materials. It is usually found in lower positions in the landscape such as footslopes and alluvial flats. This is a typical soil from the Hunter Valley, and is common also in the Tablelands and Southern Highlands. Sodosols can be very difficult soils to manage and are prone to a range of degradation problems. The overriding issue is high erosion risk, particularly gully and tunnel erosion. This is due to high exchangeable sodium, which leads to high dispersibility, and water quality problems. These soils often have poor drainage, can be waterlogged and are often saline at depth. Sodosols are identified by having a clear texture change between the topsoil and subsoil. The impermeable subsoil leads to the development of an A2 horizon in the lower topsoil which is often bleached from high lateral water movement and leaching. Subsoil structure is often striking and distinctive. Peds or soil aggregates are usually hard, and prismatic or columnar shaped. When exposed to rainfall (for example in gullies), sodic subsoils disperse and collapse readily and often exhibit a wormy surface. Many Sodosols will set hard when dry, and may form a crust at the surface. It is important to maintain the fragile upper topsoil (or A1 horizon) which protects the vulnerable subsoil beneath. Typical land uses include grazing on native and improved pastures, conservation and some cropping.