'Irrigation backwards' cuts waterlogging

By David Adams

Around six years ago Keith Slee"s paddocks were becoming so waterlogged that he was on the verge of abandoning his attempt to move from grazing to cropping.

Fortuitously, it was also about the time that raised bed cropping was starting to attract interest. He decided to try the new system and is now into his sixth consecutive crop on land he had almost given up on.

Mr Slee crops 250 hectares - a mix of wheat, barley, canola and peas - on his property near Lismore in south-west Victoria. He is one of a growing number of farmers across Australia"s high rainfall zones turning to raised bed techniques to facilitate cropping in waterlogged areas, which have limited cropping opportunities.

Described as "irrigation backwards", the technique involves forming soil beds that sit above ground level, along with a drainage system to carry away run-off.

“It"s all about reducing the risk of cropping,” says Bruce Wightman, district agronomist with the Victorian Department of Primary Industries and Southern Farming Systems - a partnership between about 1000 farmers, DPI Victoria and agribusiness companies.

Mr Wightman says the biggest risk in cropping in higher rainfall areas is waterlogging, but it can virtually be eliminated with raised beds, allowing growers to take advantage of rainfall and pursue a very high yield potential.

While many growers using raised bed techniques have reported yield increases of 25 to 30 percent as typical on land that once could not be cropped reliably, some in Wightman"s jurisdiction are starting to double, and even treble, yields as their expertise increases.

“We"re now getting up to eight-and-a-half tonnes a hectare,” he says.
While the concept of raised bed cropping has been used by horticulturalists for centuries, the use of raised beds in broadacre cropping only started in Australia in the mid-1990s through two separate GRDC-funded trials in south-west Victoria and southern Western Australia.

It is now carried out in a high rainfall belt stretching from southern NSW through south-west Victoria, parts of Tasmania and south-east SA, and around Esperance in WA.

Some Esperance growers have been using raised bed cropping to help leach salt from the topsoil.

In total, about 60,000 hectares are now estimated to be under raised beds.

“There are woolgrowers out there who are cropping for the first time using raised beds,” says Mr Wightman. “There are farming families who have been cropping for the past 80 years who are moving to raised beds.

“There are businessmen who have seen what"s going on and have negotiated with their (farm) managers to put in raised beds. There are guys who are just leasing country, who don"t own any land, who are putting in raised beds.”

Research coordinator for Southern Farming Systems, Colin Hacking, says that raised bed cropping not only has an immediate effect on waterlogged paddocks by allowing excess water to run off, but also contributes to important changes in soil structure.

“It creates a soil type which is much more free-draining,” he says.

He says that while the concept is simple enough, there are several considerations farmers need to take into account when considering raised beds. “The most important thing is to make sure the paddock is set up right.

“Not all paddocks lend themselves to raised beds. There has to be a reasonably uniform slope and you certainly wouldn"t want to be putting raised beds in steeply sloping country. Conversely, raised beds don"t work on the flat.”

Experts also stress that farmers must ensure the drainage system is correctly installed, which may mean involving neighbours to ensure run-off is properly directed.

This can include moving the excess water into holding dams - important, given concerns about herbicides entering waterways and leaching into the water-table via run-off.

Alongside the potential for crop yield increases, raised bed techniques can deliver a range of benefits in reduced tillage requirements and greater fertiliser efficiencies. The fertiliser is only applied to the crop area, not in the furrows.

Raised bed farming is also proving attractive because of the speed with which paddocks can be modified, and low establishment costs.

“The fact is, you can get into raised beds for less than $10,000,” says Mr Wightman. “Most farmers have a tractor; most farmers have some sort of sowing machine. Usually these can be modified for raised beds.”

Annual maintenance costs for raised beds are estimated at $20 to $30 a hectare, depending on whether the reshaping needed every two to three years is done by the grower or a contractor.

For growers deciding to stay with the system, most now seem to be opting for specialised, locally made machinery.

In some regions, such as south-west Victoria, this is creating a significant flow-on effect for local farm machinery manufacturers.

Mr Wightman believes the system has generated significant new business for machinery manufacturers in the Geelong area alone, illustrating the economic spin-off that can occur through farmer innovation.

For more information:
Bruce Wightman, 03 5226 4667, bruce.wightman@dse.vic.gov.au
Col Hacking, 03 5229 0566, sfso@pipeline.com.au

GRDC Research code: SFS 00007, program 4

Region North, South, West