Recent studies are making the case for subsurface drainage, with findings that there has been an almost two-fold increase in yields compared to an undrained waterlogged site.
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The study, undertaken by South Coast Natural Resource Management (South Coast NRM) and Stirlings to Coast Farmers, is in its third year and is investigating subsurface drainage return-on-investment.
After two consecutive wet seasons in south west Western Australia, it is estimated about three million hectares of land is subject to waterlogging or inundation.
The trial is across four waterlogged sites in the Esperance and Albany zones.
Dalyup farmer Rohan Marold said during the 2022 harvest, it was a problem getting harvesters across the paddocks that had been deep ripped, with Mr Marold's machinery getting bogged multiple times.
"We used a consultant to do some digital elevation mapping to see where the water was flowing and where we needed to get to with the drains," Mr Marold said.
He started installing subsurface drainage pipes on heavy clay paddocks, but he found it wasn't as successful at getting the water out of the profile, because of the sodicity and subsoil.
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The project then tried installing the pipes on sand over clay and the pipe started flowing within 24 hours.
"It's pretty satisfying to see the water coming out of the pipes after you've installed them and it's nice, clear water," Mr Marold said.
"It's different to seeing water running off the top of your paddock with all that nutrient loss and erosion."
The installation of subsurface drains involved the use of a tile plough attached to a tractor.
The tile plough uses GPS technology to create a ripping point, the plough then creates a trench, lays the plastic slotted pipe and buries it under the subsurface.
Mr Marold said the aim was to lay the pipes at least 600-800 millimetres deep to avoid any damage from machines or deep ripping.
South Coast NRM regional agricultural landcare facilitator Sophie Willsher said the project findings had solidified that subsurface drainage was effective at moving perched water away from the root zone, leading to maximised yield potentials.
Ms Willsher said one of the most important things to consider was the elevation of the paddock before installing subsurface drainage.
"It's always best to work with gravity," Ms Willsher said.
"You also should consider your soil profile and the depths to the clay layer, which is the impenetrable layer where most perched water will sit.
"Considering soil type and, of course, other factors on-farm, including salinity levels, are important in making sure that your drainage is designed best for your property."
Ms Willsher said the project had monitored the biomass, weed and disease presence and soil moisture conditions of paddocks in the trial to produce a final return-on-investment figure in 2024.
"We're looking forward to seeing the final return-on-investment figure and how we can apply this to support broader scale adoption for growers," she said.
The project is funded by the Grains Research and Development Corporation (GRDC), whose investment in addressing waterlogging ranged from subsurface drainage projects through to genetic research.
GRDC grower relations manager west Luke Dawson said the project will help growers and advisers compare the yield penalty in undrained areas with the capital investment and gains of installing drainage.
"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," Mr Dawson said.
