Student Solves Soil Mystery

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26th May 2009, 05:04pm - Views: 1041

Student Solves Soil Mystery

When a group of South Australian farmers took action to combat dryland salinity, they

were puzzled to find that their soils were still degrading and their pastures suffering.

The farmers, members of the Keilira Farm Management Group (KFMG) in the state’s

upper south-east, called the Future Farm Industries Cooperative Research Centre in to


PhD student Melissa Fraser, of the CRC, found that the ailing pasture was largely

confined to clay-rich soils common to the area, about 242 km south-east of Adelaide.

“There are two distinct soil types throughout the Keilira district—a deep, clay-rich soil

and a shallow sandy soil overlying limestone,” she said.

The combined effects of climate change and artificial drainage had reduced salinity but

left high levels of positively-charged sodium ions in the soil, leading to another land

degradation problem, called sodicity.

“When these soils become wet, the sodium causes dispersion,” she said. “Fine clay

particles move down through the soil, blocking the pores essential for holding the air and

water that is vital for plant growth.” Sodicity affects more than 60 per cent of Australia’s

cropping land. The Keilira farms had soil types predisposed to it.

Ms Fraser worked with KFMG as part of her PhD project, hosting field walks and

attending field daysin conjunction with the farming group. The aim was to inform local

land managers, agronomists and consultants of the variability in soil types and the

interaction of salinity and sodicity. The work was supported by KFMG and the South

East Natural Resource Management board.

The farmers are now treating their soil with gypsum, seen widely as one of the best

defences against sodicity.

Ms Fraser is one of eight early career scientists invited to present their research results at

the Cooperative Research Centres Association’s Pathfinders Conference at the National

Convention Centre in Canberra this week. The CRCA represents Australia’s 50 CRCs

operating under a federal government program to drive public/private sector research.


Greg Lawrence Ph 0429101 675 E:

CRCA Media Ph 0419 250 815; Email

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