Moisture management destined to be a legacy
GroundCover™ Issue: 124 | 29 Aug 2016 | Author: Brad Collis
Growers in the far north of the Western Australian wheatbelt are showing just how much has changed as managing a drying climate in an already low-rainfall region becomes almost routine
Low rainfall has been an ongoing challenge for growers battling over the years to make a living off the sandplain country in Western Australia’s far northern wheatbelt. But persistence tends to pay off around Binnu, 520 kilometres north of Perth, where second and third-generation wheat growers are today emerging from the struggle of their parents’ and grandparents’ eras and embedding agricultural resilience into their district’s short history.
As a town, Binnu is really just a roadhouse, primary school and grain-receival depot. Its official archive is short on milestones: gazetted in 1932 near the site of an old well, opened to conditional purchase farming in the 1960s, and challenged ever since by periodic drought, the occasional mouse plague and scares such as soil salinity.
It has been a tough landscape to farm, but a landscape that is today responding healthily to modern conservation farming systems. In districts such as this in WA’s mid-west every generation is a pioneer as knowledge accumulates and new farming practices are developed. East Binnu farmer Piet Diepeveen exemplifies this, hosting long-running controlled-traffic farming (CTF) and deep-ripping trials that are part of a fundamental shift in grain growing in the region.
On a property taken up by his father Joe in 1963 as a conditional purchase block, Piet is in the vanguard of a new cropping system that shows every sign of being able to withstand a drying climate that a decade ago would have spelled the end of profitable cropping. Piet and other growers in the region are taking the whole concept of water use efficiency to new levels, prioritising the capture and preservation of every drop of rain that falls from a distinctly shifting weather pattern.
Piet says the average annual rainfall would not be more than 300 millimetres now: “It’s at least 25mm less than a decade or so ago, plus there has been a shift to more summer rain and longer dry spells between rain events in the winter,” he says.
“This means we have to conserve that summer moisture and be able to access it during the growing season. Weed control is now everyone’s summer obsession. You see a tinge of green and you act; you don’t let any summer weeds grow.”
The area in which Piet has become prominent in the district is deep-ripping, through trials he has been hosting for the Department of Agriculture and Food, WA (DAFWA), researcher Paul Blackwell.
He says the collaboration stemmed from observing mould-boarding and spading trials further south: “We could see the benefits, but here in a lower-rainfall area those operations would cost more than the land is worth. But we have found deep-ripping puts similar soil-amelioration goals within economic reach.”
The basic concept is straightforward: to rip a furrow deep enough to provide a passage for crop roots through a hardpan that exists at the 30 to 40-centimetre level. Breaking this layer allows the crop to access deeper stored moisture as the season advances.
But there have been numerous side issues to work through, from managing nutrients at depth, the need to avoid disturbing sodic layers, the need to stop crops getting away too quickly and ‘haying off’ later in the season, not to mention the upfront costs of fuel and machinery.
“The deep-ripping program came from realising we simply needed to get the crop roots deeper because access to stored soil moisture has become crucial,” Piet says.
“And there is a hardpan we needed to get through. We deep-rip to 450mm and even 600mm if we can.”
The pay-off in breaking up that hardpan has been significant. The deep ripping alone began delivering an extra 700 kilograms per hectare of wheat, but then Piet started working with Paul Blackwell on his concept for inclusion plates. These hold open the furrow long enough for loose topsoil and organic matter to drop deeper into the profile. Piet says this has delivered a further 700kg/ha in yield improvement.
“So we are averaging an extra 1.4 tonnes/hectare from the combined effects of deep ripping and the inclusion plates,” Piet says. “At a cost of $40 to $50 a hectare that’s a very profitable gain.”
How often the operation will need to be repeated has yet to be determined. DAFWA researchers believe the positive yield gains should last for up to nine years if a grower also implements CTF to prevent soil re-compaction.
However, Piet also points out that when trying to get as deep as 600mm it often cannot be done in one run.
“It can be asking a lot to pull a 40-foot ripper at 500 to 600mm depth in one go, so you might rip to 450mm one year and follow up a few years later at 500 to 600mm.”
The DAFWA researchers have also been trialling the use of shallow leading tynes working at 10cm in line and ahead of the deep-ripping tyne. They have found this can reduce the draft force by up to 18 per cent on clay-textured soil, and by 10 per cent on sandy-textured soils.
Piet has introduced CTF, allowing him to get the job done with a Track 8370RT tractor working on tramlines. “Blokes that haven’t yet started tramlining are needing 600hp tractors to deep-rip,” he says.
“But we also need the tramlines because it’s been 25 years since we took sheep off the cropping area and introduced no-till, so our soils are quite soft.”
Different approaches, same goals
Piet says most growers in the district are working out how best to approach deep-ripping, one way or another: “Everyone is always trying different ideas, but, whatever the approach, the common goal is to look after soil moisture. That’s the key.”
Aside from deep-ripping, he says the other big impacts from grains research have, for him, been Roundup Ready® canola and Mace wheat in terms of improved weed control and crop options.
“We’ve moved from the traditional wheat–lupin rotation on our yellow sands to a quarter canola, quarter lupins and half wheat. We couldn’t control weeds in the lupins, but Roundup Ready® canola has provided the break crop and the weed-control options we need.
“We’ve also done quite a bit of work with wide rows in lupins and canola. The wider rows definitely seem a better option in lighter rainfall years, although the wide gap in the crop meant grain would come onto the harvester belt and bounce around, and off, because there wasn’t the volume to hold it together. So we’ve now moved to ‘two rip, one skip’ – two rows and skip a row which doesn’t leave such a big tramline gap.”
For nutrient management (mainly nitrogen and potash) Piet says he “dabbled” in variable rate (VR) technology, but decided in the end to keep everything simple: “Basically this means not putting in much upfront, but waiting until we know how the season is likely to pan out.
“The exception is when wheat follows canola, which takes out more nitrogen. We apply ammonium sulfate over summer as an up-front, low-cost nitrogen source then wait for the three-leaf stage and look at how the crop is going, how much rain we have had, and what the forecast is.”
This season 75 per cent of the program had to be sown dry – all the lupins, all the canola and half the wheat: “We didn’t get a start until 22 May with 8mm of rain, then a 21mm follow-up on 25 May. Since then, germination has been good with two more rain events in June.”
Since his father started cropping 53 years ago, Piet has witnessed a lot of change, but says this is what he finds most fascinating about the business.
“I remember back in 2006 when we were in a dry period (a devastating two-year drought) I went to Esperance to a mate’s wedding and saw GPS technology in action. All I could see were opportunities.”
Every season is different and being overlaid by a changing climate and changing management practices in response. But for Piet, the challenges of grain growing are not so much the technical elements, but the social backdrop to farming: “People talk about the challenges and opportunities in front of us, but for me the biggest concern is lack of people in rural areas to support community services such as schools.”
Compared to that, Piet almost makes the on-farm challenges straightforward: “We just need a good system in place to grow high-quality grain, then, as an industry, looking after that grain on its journey to port and markets.
“Of course that does need an industry in which everyone is working together,” he adds with quiet perspicacity.
More information:Piet Diepeveen,
GRDC Project Code DAW00243, MIG00016-A
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