Soil management

Erosion

Soil erosion is widespread and irreversible. Although weathering and erosion are natural and important processes, human activities often accelerate the movement and loss of valuable soil.

Soil erosion occurs when soils are exposed to the forces of water, wind and gravity. When vegetation cover is cleared, or lost due to over stocking or over cultivation, the force of the wind on the soil surface increases, causing erosion. The same soil surface exposed to falling raindrops and run-off is also vulnerable to erosion from water. Sodic soils are extremely vulnerable to erosive forces and require special management.

Erosion has many impacts, particularly for farmers and landowners. It reduces fertility and productivity, stripping the soil of valuable nutrients and minerals. Lost soil becomes entrained in run-off, often choking and polluting waterways, and damaging public utilities.

Treating existing erosion, particularly gully and stream bank erosion, can be costly. All landowners should seek specialist advice about minimising, controlling and treating erosion.

What you can do

• Maintain between 80 and 100 percent groundcover vegetation of mostly native perennial grasses.
• Learn about the qualities and properties of soil on your property and learn about treating and preventing erosion through the NSW Department of Primary Industries.
• Use fences to control or prevent stock access to gullies, waterways and riparian areas. Consider using alternative troughs to water stock.
• Revegetate exposed soil with perennial grass species.

Soil sodicity

Sodicity is caused by high concentrations of sodium which is generally attached to clay particles of the soil. As a result, clay particles in the soil lose their tendency to stick together when wet. This leads to unstable soils that may erode or become impermeable to water and plant roots.

Signs of sodic soil are poor water infiltration, surface crusting, water logging, collapsing areas which appear to result from underground tunnelling and piping, and cloudy water in dams and creeks that never settles out.

Sodicity is most common in the subsoil. Soil structural problems from sodicity increase when soil organic matter is low. Having a good groundcover helps stabilise the topsoil and retain its organic matter content, and the risk of sodic subsoils becoming exposed to run-off and erosion is reduced.

What you can do

• Maintain more than 80 percent groundcover to improve soil structure and increase soil organic matter
• Look for signs of sodic soils on your property (soil crusting, soil sealing, dense and compacted soil, sign of water logging, cloudy water in streams and dams)
• Know where the sodic soils are on your farm
• Retain topsoil and minimise disturbance and exposure of sodic soils
• Exclude stock from eroded gullies and revegetate to prevent further erosion
• Conduct a soil test that includes a measure of the Exchangeable Sodium Percentage (ESP) - ESP of 6 percent or more indicates a sodic soil.
• Get advice from your Local Land Service or NSW Department of Primary Industries before treating your soil.

Soil acidity

Acid soil has a pH of less than 7.0. The pH of soil is a measure of its relative acidity or alkalinity.

While different plants have different tolerances to acidity, most agricultural plants do best when the soil pH is between 5.0 and 6.5. But when the pH drops below 5.0, plants that are very sensitive to acidity, such as barley and lucerne, become adversely affected.

Acid soil is a major cause of land degradation in some areas, resulting in a loss of groundcover, increased soil erosion and lower productivity. However, it is a slow and subtle process brought about, in part, by agricultural production.

Agriculture may contribute to soil acidity by:

• lack of deep-rooted perennial grasses to catch nitrogen before it leaches below the root zone (e.g. clover dominant pastures or mainly annual pastures)
• removing alkaline plant and animal produce (e.g. lucerne hay cutting)
• continuous use of fertilisers high in nitrogen (e.g. ammonium sulphate and mono-ammonium phosphate).

Some effects of soil acidity are:

• lower agricultural production rates from less vigorous pasture
• higher production costs (e.g. need to add lime to soil and greater weed control)
• loss of groundcover, leading to soil erosion and lower water quality
• less water use by vegetation, contributing to salinity.

What you can do

• Use deep-rooted perennial pastures to improve nitrogen recycling and slow the rate of acidification
• Use lime to raise soil pH
• Use plants that can tolerate acid soil
• Get advice from a qualified adviser before treating your soil, learn more at NSW Department of Primary Industries.

Dryland salinity

Dryland salinity is caused when groundwater seeps to the surface, bringing salt with it. As the soil surface dries out, salt is left behind.

Recognising and managing dryland salinity not only helps protect water quality, but also helps to maximise productivity and economic returns on your farm.

Dryland salinity is a problem for farmers because salt makes it harder for plants to extract water from soil. The result is loss of pasture and groundcover, and eventually soil erosion, which affects the productivity and sustainability of your farm.

One of the major causes has been removing deep-rooted perennial vegetation and replacing it with shallow-rooted pastures and crops, raising the water table and bringing salt to the surface.

The effects of dryland salinity include:

• loss of groundcover and pasture production
• salt deposits on the soil surface
• increased soil erosion
• tree death
• increased salt concentrations in dams and creeks
• water logging.

Look for the tell-tale signs - crystal clear dam water, bare patches of ground with a white surface crust (salt scalds) and invasion by salt tolerant plants such as Couch, sea Barley Grass and Buck's Horn Plantain.

What you can do

• Manage saline areas and salt scalds
• Promote plant growth and use plant species to maximise soil water use
• Revegetate hills, ridge tops and other recharge areas
• Get advice from the relevant authorities before treating your soil, learn more at NSW Department of Primary Industries.