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 investigate.
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 days in 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.
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