Soil is the top layer of the earth’s surface and varies in depth and make-up.   It is made up of rock, mineral matter, organic matter, water and air. The ratio of these components and the soil layer depth contributes to creating vastly different types of soils which can be identified by properties including texture, bulk density, colour and structure.

South Australia has three distinct landscape types with siliceous dunes, sand spreads and dune fields common to all three areas. To the west a series of calcareous coastal dunes corresponding to the current coastline and associated inter-dunal flats form a plain. The north-eastern area is an elevated clay plain.  To the south a marine limestone plain with dark loamy soils and pockets of fertile soils overlie volcanic basalt.

Soil health and quality are inextricably linked to the health and well-being of other natural resources including water.  The capacity of soil to function within eco-system boundaries has an impact upon sustainable productivity, environmental quality and the welfare of plants and animals.

Degradation refers to the decline in a soil’s fertility due to loss of organic matter, wind or water erosion, salinity, chemical contamination, acidification or other means. Since European settlement over 10 million hectares of land in South Australia’s agricultural zones has been cleared of native vegetation. This clearance, combined with unsustainable farming practices has resulted in the majority of this land suffering some form of degradation.

In South Australia the threats to our soils are significant and coordinated and continued work is vital to ensuring long-term success in reducing the rate of degradation to our soils.   

Threats to SA Soils:

• 800,000 hectares of cleared land with high inherent susceptibility to water erosion
• 2.4 million hectares of cleared agricultural land with high inherent susceptibility to wind erosion
• 900,000 hectares of cleared agricultural land with degraded topsoils due to acidity
• 326,000 hectares of agricultural land and 80,000 hectares of remnant native vegetation affected by salinity
• 6.5 million hectares of agricultural land with low inherent fertility
• 2.5 million hectares of agricultural land with high inherent risk of being affected by water repellence.

 Soils are partially renewable, however current renewal rates are inadequate when compared to current rates of degradation.  There are well-known improvement techniques and land management systems which can be adopted, increased and improved upon to better manage this vital natural resource.

What can you do?

•  Reduction of Water and Wind Erosion Risk Indices (reducing exposure of agricultural soils)
• Adopting direct drill/no till and appropriate grazing practices
• Increases in annual application of lime, to exceed current acidification rate
• Planning for no increase in salinised land beyond Year 2000 levels
• Continued development of drainage structures to transport saline/non saline water out of ‘at risk’ areas
• Improvement in water use efficiency of agricultural crops and pastures
• Management of irrigation drainage
• Large-scale habitat re-establishment
• Substantial expansion in rates of revegetation

Source: Soil Conservation and Land Management Directions for the Agricultural Lands of South Australia. South Australian Soil Conversation Council 2005.