Could subsurface drainage help WA’s waterlogging woes?

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Cally DupeThe West Australian
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A subsurface slotted drainage pipe is installed at the Cranbrook trial site.
Camera IconA subsurface slotted drainage pipe is installed at the Cranbrook trial site. Credit: Rachel Asquith

Subsurface drainage system studies are ramping up in WA after heavy rains caused widespread waterlogging problems in the southern parts of the State.

Grains Research Development Corporation issued a warning to growers this week that waterlogging could lead to soil structural decline.

It could also create nutrient deficiencies and toxicities, cause root death or reduced plant growth, or even plant death.

GRDC invests about $2 million a year in waterlogging-addressing projects with work ranging from the new sub-surface drainage projects to genetic research.

The research group has initiated two new, three-year sub-surface drainage investments in WA to help growers manage the effects of waterlogging.

It hopes to help growers implement strategies to realise crop yield potential and boost profitability by address the impacts of waterlogging.

Demonstration sites have been set up at Cranbrook, in the Albany Port Zone, and Neridup in the Esperance Port Zone.

GRDC grower relations manager — west Rachel Asquith said the projects would compare yield penalty in drained and undrained areas.

This included pitting the yield penalty in undrained areas with the capital investment and gains of installing drainage.

“Subsurface drainage is widely used in other industries and for high-value crops,” she said.

“The returns have not been established for cropping in WA’s south-western grainbelt.

“We want to demonstrate that a strategic drainage investment can add real value.”

The projects originated from discussions initiated through the now-defunct GRDC Grower Network.

Ms Asquith said grower participation was a key part of planning, developing, monitoring and maintaining the trials.

Stirlings to Coast Farmers has partnered with GRDC to run the Cranbrook project, installing a weather station and soil moisture probes at the site.

It has also mapped the site to establish water flows and water accumulation locations.

Subsurface drainage is widely used in other industries and for high-value crops.

Rachel Asquith

South Coast Natural Resource Management is coordinating the Esperance demonstration, undertaking ground works at Neridup.

The group will share capacity and resources with Stirlings to Coast Farmers, which is managing the remote sensing for both sites.

Monitoring will this year and during the next two growing seasons to record soil volumetric water content, weed and disease pressure, plant establishment and tiller counts.

GRDC and the two groups will measure biomass using satellite normalised difference vegetation imagery.

Yield analysis, plant density analysis and basic gross margins will be measured annually before the final return on investment analyses are completed by South Coast NRM.

It has been estimated that approximately three million hectares of land may be subject to waterlogging or inundation across the South West agricultural region of WA.

Ms Asquith said most cereal varieties were “poorly evolved for waterlogging”, which was a highly seasonal issue creating a lot of risk around investing in effective mitigation.

“This year, the costs to manage waterlogging or deal with issues such as bogged machinery will be much more significant than in 2020,” she said.

“Our aim is to give growers data that lets them assess the cost of installing subsurface drainage against the potential to recover some of those losses by improving yields.”

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