Unproductive saline patches in research sights

Commissioned by the Murraylands and Riverland Landscape Board and Ag Innovation & Research EP, results from 100 participating farmers showed a conservative total of 50,000 hectares had been impacted, causing up to $50 million in losses in the past 10 years.

Insight Extension for Agriculture's Chris McDonough, who prepared a report on the findings with AIR EP's Naomi Scholz, said the unproductive area had the potential to double, with research and trials needed to tackle the growing issue.

Dr McDonough said the unproductive bare patches were caused by rising salinity, restricting and often decimating crop growth, but the underlying reasons as to why the salinity was occurring were less clear.

"It appears most likely that it is salt that is coming from within the soils beneath," he said.

"It is not a seep situation where there's a perched water table, but the natural salts in soil that during the drier periods in particular is coming to the surface.

"That has been exacerbated where there have been a number of dry seasons consecutively because there's nothing growing there to stop capillary rise and evaporation bringing salts to the surface."

Of farmers surveyed, 36 per cent said they had 50ha or more impacted, with some reporting unproductive saline patches totalling up to 2500ha.

Dr McDonough said farmers had tried a variety of management options with varying success and were seeking further information on underlying causes, how the problem expressed itself in different landscapes and possible solutions.

"Putting hay, chaff or sand out, to create a mulching effect, to stop the salinity getting to the surface has showed promising signs but there's a lot of time and cost involved," Dr McDonough said.

"You can do it reasonably well on a small scale, but on a large scale it can be an expensive exercise. When patches have been wet up to flush the salt out (simulating heavy rains), it just moves down and is there to come back up once it gets hot again.

"Getting on top of this problem while it's still in a smaller, patchy state is important in efforts to hold it at bay. Patches can go past the point of no return if nothing is done."

Dr McDonough said in an ideal scenario, funding would be secured to conduct long-term trials to examine salinity levels across time and during different management techniques.

"Hopefully that will enable us to figure out what methods will work and what will work for longer," he said.

INSIGHT Extension for Agriculture's Chris McDonough and PIRSA's Brian Hughes were digging pits to examine the differences in soil composition and characteristics between dry saline patches and the surrounding unaffected cropping ground south east of Waikerie last week.

Property owner Glynn Schmidt said up to 200ha of his cropping ground had been reduced to unproductive dry saline patches.

"We've been dealing with them for the past six to eight years and the concern is they're getting worse every year," he said.

"They started off as small patches and they've been increasing in size every year. The yield just about goes down to zero on those areas."

Mr Schmidt said they had particularly noticed the problem on their grey soil and stonier ground.

Survey results showed that the issue was prominent on clay and clay loam soils on the Eyre Peninsula, with Murray Mallee farmers reporting clay loam and shallow stone soils were both affected.

Mr Schmidt said they had experimented with management strategies to improve the saline patches and the best results they'd had, had come from putting a layer of sand over the top of the impacted areas.

"That has brought production back but it takes quite a bit of sand to cover these areas, which involves time, cost and finding sand available to do it," he said.

"It's becoming a large problem across the district so we're happy to see some work being done on it."

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