5.3.3. Soil health
According to the Australian Natural Resources Atlas, the Murrumbidgee river transports 4,665,626 tonnes of sediment per year, well above the national median value of 166,621 tonnes per year. This is supplied largely by gully and riverbank erosion. A report by CSIRO suggests that gullies occupy 89,000 kilometres within the Murray-Darling Basin (Hughes and Prosser, 2003), representing a major source of land degradation.
Wind erosion and gullying are often caused by inappropriate land-management techniques. The extent of groundcover is of primary importance, as groundcover intercepts rain as it falls and slows runoff, reducing the impact of water flows on the soil. Wind erosion can also be minimised by maintaining roughly 40-65% groundcover (NSW DPI and Murrumbidgee CMA, n.d.). In the Murrumbidgee region, soil is most sensitive to rainfall-induced erosion in summer (February, in particular). The risk is minimal in winter. A survey of 700 landholders in the Murrumbidgee region reported that 75% of respondents attempted to maintain at least 50% groundcover, with almost a third of these attempting to maintain 100% groundcover (Davis, n.d.). This higher target was more common among managers of smaller properties.
Other issues reported in the survey include soil compaction. 45% of respondents reported that soil compaction was an issue on their properties. Stock and machinery were both considered a major cause of soil compaction by roughly 40% of those who reported an issue with soil compaction.
References and Resources
• Australian Government. 2000-2002. Australian Natural Resources Atlas: Soils – Murrumbidgee River.
• Davis, V (Murrumbidgee CMA). Undated. Dryland Farming Systems Survey: Final Report.
• NSW DPI, Murrumbidgee CMA and Grain & Graze. 2008. Ground cover in the mid-Murrumbidgee catchment.
