Bedding down for next season
At a glance
- Raised beds provide better drainage in high rainfall zones and are good for soil structure
- Study found black, self-mulching soils with high clay content best suited to raised beds
- Farmers urged to use best practice guidelines
Grain growers in high rainfall zones are being encouraged to consider raised beds as they start planning for next season.
DPI soils extension officer Tim Johnston said although raised beds had been around for many years, there was little uptake in recent times because of drought.
But Mr Johnston said the high rainfall last season had highlighted the need to provide adequate drainage to avoid water logging.
And he said raised beds offered considerable benefits in terms of improved soil structure, better risk management and increased profits.
Firm foundations
Mr Johnston said broadacre raised beds first came onto the scene in the middle of the 1990s, with the formation of the Southern Farming Systems (SFS) group.
“SFS began when a group of farmers recognised the potential for cropping in south west Victoria, but they also recognised waterlogging was their biggest constraint.
“So, a group of farmers in collaboration with DPI agronomists, notably Bruce Wightman and Chris Bluett, looked at methods of drainage, including underground drainage, pipe drainage and 30m wide raised beds, called humps and hollows.
“After a couple of years of trials they decided to settle on the raised beds.”
Mr Johnston said in the first five years there was considerable uptake of raised bed technology.
“By the late 1990s raised beds were recognised as an excellent way of alleviating waterlogging and reducing risk in wet years.”
Raising the benefits
Mr Johnston said the potential benefits of using raised beds is significant, including better drainage and improved soil structure.
“It’s really compulsory controlled traffic because the tractor wheels go up and down the furrows, so the main bed is uncompacted by the wheels of tractors,” he said.
“The incorporation of raised beds means the failure of crops due to water logging is reduced.”
“When you consider the furrow in a two metre bed takes up 20–30 per cent of your land and you’re not putting the fertiliser in that you can essentially reduce your fertiliser bill by 20–30 per cent,” Mr Johnston said.
“All of these factors contributed to higher profits.
“Particularly if they’re set up correctly you can get quite high yielding crops off raised beds in wet and dry seasons.”
Planning, planning, planning
Farmers need to consider their raised beds as a part of general on-farm planning.
“You need to make sure that water can actually be removed from the paddock easily,” Mr Johnston said.
“Growers need to consider which system best suits their requirements. Two metre wide beds may be the best option for some, while others may prefer three metre wide beds to fit into their larger controlled traffic systems.”
First step, Mr Johnston said, is organising a surveyor to carry out accurate contour surveys down to 10cm intervals (see Figure 1).
FIGURE 1 - The contour survey will accurately show paddock slopes and facilitate the best plan for beds and drain direction
While many surveyors are located around Shepparton, he said there were also a couple located in the south west.
“When using the contour survey as part of a whole farm plan you need to consider soil type, the slopes for the raised beds and the appropriate alignment of those beds across slopes”, Mr Johnston said.
While some of the biggest grain growers in the south west might already be getting contour surveys and whole farm plans done, others could also benefit from their uptake (see Figure 2).
FIGURE 2 - It is recommended that a farm plan be designed so overall water movement, tree lines and buffer dams can be incorporated with other enterprises
“Potentially the smaller guys putting in 20–30 hectares themselves may not need a survey and they’re probably the ones that are not going to benefit from raised beds,” Mr Johnston said.
“We have lots of comments from farmers saying my crop still gets waterlogged on raised beds - that’s probably because they’re not draining better as they have been poorly planned and installed.”
Mr Johnston also noted that not all paddocks were suitable for raised beds.
He said it was important to consider surface water movement and the having well-formed headlands where the tractor turns around to avoid getting bogged.
Slowing the flows
To reduce off-farm nutrient loss and potential flash flooding, Mr Johnston recommended well managed grass water ways, which can catch sediment that nutrients may be attached to and buffer dams that capture run off and slow water run-off.
“Raised beds don’t necessarily increase the amount of run off, but they do increase the speed that the water comes off the paddock,” he said.
“A buffer dam is like a big shock absorber, so it can be let out at a slower rate later on to reduce the risk of flash flooding downstream.”
Although buffer dams are not common, Southern Farming System’s two concept farms at Inverleigh and Winchelsea have both invested in them.
The concept farms were set up in the late 1990s to demonstrate the best practice at the time.
Mr Johnston said farmers also needed to carefully consider the arrangement of their raised beds and the maximum slopes for their soil types.
“So, for heavy textured top soils (for example heavy clays), slopes should not exceed 1.5 per cent - that is 1.5m in 100m and for light textured topsoils (sandy clay loams), slopes should not exceed 0.5 per cent.”
Thinking green
Mr Johnston said his interest in raised beds was sparked in the late 1990s when concerns were raised about the potential impact of the increased run-off that came with the change of land use in the south west of Victoria from conventional grazing to raised bed cropping.
“I have a general interest in environmental issues and there had been a real lack of research into nutrient losses in run-off, particularly in high rainfall cropping regions.
“There was also a genuine interest from Catchment Management Authorities to do this type of research.”
Thanks to DPI and Grains Research Development Corporation funding and the SFS, Mr Johnston set up a replicated trial near Winchelsea to compare traditional flat cropping with raised beds.
The trial ran a three-year rotation of canola, wheat and barley, which is typical for most grain growers in the south west region.
“The raised bed involved an initial deep cultivation to a depth of 20–30cm,” Mr Johnston said.
“The depth depends on how much soil moisture there is. If there’s a little bit of moisture you can get a bit more depth.
“Once you’ve done the deep cultivation, a machine called a bed former is drawn through the cultivated soil and the soil from the furrow from where the bed former is drawn is thrown on top of the bed.
“Typically a two metre wide raised bed would raise about two inches in height hence the term raised bed.
“At the bottom of each plot, we had water sampling equipment, an automatic water sampler and a water level measuring device to measure the volume of flow of water, with water samples taken at pre-determined flow volumes.
The water samples were analysed for nitrogen and phosphorus to make a comparison of how much nutrients come off the raised bed compared to flat cropping.
Research findings
The study found that black, self-mulching soils with a high clay content of more than 30 per cent are best suited to raised beds, while sodic soils (sodium rich) required more careful management.
“If sodic soils continue to be saturated in a wet season like we’ve had a lot of the soil structure is lost,” Mr Johnston said.
From the results of the six-year study, Mr Johnston set up best management practice guidelines for raised bed cropping that are available online.
The guidelines relate to sowing to minimise water flow, nutrient management to reduce fertiliser losses through run-off and sites for raised beds.
Mr Johnston said it was particularly important for growers to adhere to the guidelines due to the potential for raised beds to release relatively high annual loads of nutrients in run-off, most of which is in a dissolved form.
“There are limited opportunities to remove dissolved nutrients from run-off, so we need to prevent nutrients getting into our waterways with improved water and nutrient management.
“There is also potential to harvest water running off beds for storage on-farm.”
Why raised beds now?
Mr Johnston said raised beds were now more relevant than ever.
“Raised beds came in during the late 1990s and since then we’ve had some pretty dry periods until last year.
“Many properties have had a change of managers - the old guys have moved on and younger farmers have come in.
“They haven’t been exposed to raised beds and historically wet seasons.”
Mr Johnston said last year waterlogging was a big issue in the south west, particularly for younger farmers who have not experienced heavy downpours.
Thinking about the future, he said raised beds would become increasingly important.
“Having done a lot of climate change work and seeing how climate variability is going to increase, becoming more intense in wet and dry periods, the use of raised beds will be useful as a risk management tool for all conditions.”
Case study: Raised beds insurance
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John Sheehan |
Snapshot
Project name: Environmental Impacts of Raised Bed Cropping in South West Victoria
Project team: DPI: Tim Johnston
Project website: GRDC - High Rainfall Zone, SFS - Hi Grain (PDF)
Project funding: DPI, GRDC
Location: South West Victoria
Timeframe: June 1999 to June 2006
Contact: Tim Johnston
Email: tim.johnston@dpi.vic.gov.au
John Sheehan, general manager of Yaloak Estate at Ballan and Derrinallum, describes raised beds as another form of farm insurance.
“We insure our crops for fire and hail. This is water logging insurance,” Mr Sheehan said.
The properties run 7000 acres of cropping, 6000 of which is on raised beds.
They were first installed more than 10 years ago and the beds have provided significant benefits to the Yaloak Estate bottom line.
“They’ve certainly saved our cropping system this year,” Mr Sheehan said.
In 2010, they also proved essential.
“Last year was a real example of the benefits of the beds - they worked overtime.”
Mr Sheehan said farmers concerned about the cost, shouldn’t be.
“A lot of farmers that haven’t been involved in beds may be concerned with the capital investment, but you can clearly justify it in one year.”
Mr Sheehan said the outlay required had been reduced since the beds were first introduced, thanks to the bed-width changing from 1.7m to 2m to better suit today’s machinery.
He put in his first raised beds just as Southern Farming Systems began introducing them to the area as a way of extending his cropping to areas of the farm prone to waterlogging.
The results were surprising.
“Certainly the management of the water has been the biggest factor, but the incidental benefits that have come with it are probably greater in the scheme of things,” Mr Sheehan said.
“The soil structure in the beds is so much superior to conventional farming and we get controlled traffic by default. We can only tram track the drains so all machines have been modified to fit the beds.”
The raised bed system enables Mr Sheehan to run an intensive farming system.
“We wouldn’t be able to do intensive cropping without raised beds.”
Mr Sheehan believes uptake in the Western District and the associated changes have been significant.
“Most of the big operators now are all running raised beds. It’s a complete shift.
“It’s a whole farming system. Don’t do it half-heartedly, do it properly and you’ll see the benefits.”
