Many growers were unprepared for the onslaught of 2022, which wrote itself into the history books as one of the wettest cropping seasons on record for much of eastern Australia.
Even those in high-rainfall zones who are accustomed to dealing with saturated soils and waterlogged crops were caught out by the intensity, extent and duration of flooding.
They include Rutherglen mixed farmer Andrew Russell, who says the experience has prompted a renewed focus on improving drainage across his 2500 hectares of cropping country in north-eastern Victoria.
Andrew says last year also highlighted how hamstrung growers are to “manage anything” during a wet year. “In a drought, we can still get out and we can do fencing or any other paddock operations,” he says. “In 2022, we felt paralysed because we couldn’t get anything out of the shed.”
He says he was extremely relieved once paddocks dried out. “Drainage is absolutely our number one to do, as much as we possibly can, now that we’ve got the dry weather and we can actually perform that work.”
Spared by dry winter
Southern Farming Systems senior research and extension officer Greta Duff says a relatively dry winter spared many crops from waterlogging during the critical growth period.
Waterlogging each season is the main issue raised by growers in the high-rainfall zone (HRZ) across southern Victoria and northern Tasmania. On 13 October – Greta remembers the date because it was her birthday – there was 12 hours of non-stop rain.
“That’s when we were getting concerned because we’d seen it all through the Wimmera and Mallee through September that they had had a lot of rainfall and ... come October, it hit us torrentially,” she says.
The impact varied according to the severity of waterlogging and how long it stayed. In some paddocks the crops died, while in others yield was reduced by the stress and retillering in barley hampered harvest.
Ms Duff, who has led research that aims to help growers recover waterlogged crops, says many growers in the HRZ benefited from putting drainage into paddocks that were prone to waterlogging, and found the adoption of controlled-traffic farming reduced the likelihood of bogged machinery.
“Some farms can just get away with laser levelling on the top to change the gradient, or use a Wolverine to create ditches; other farms might need to put in some subsurface drainage because there’s too much water coming through,” she says.
“You really need to take a look at your farm for what’s going to suit it best, and also what’s going to suit your budget because it’s pricey putting drainage in.”
Two GRDC projects investigating subsurface drainage are underway in south-western Western Australia, where waterlogging is a common problem affecting up to three million hectares of land and causing yield losses of up to 2.5 tonnes/ha.
Data gathered from demonstration sites in the Great Southern region and Esperance Port Zone is being analysed to calculate return on investment from using slotted pipes to reduce waterlogging.
Elevation mapping was used to produce contour maps, watershed maps, streamflow accumulation and pooling point maps to guide pipe installation at depths between 50 centimetres and 1.5 metres.
A ‘trench-cutter’-type machine dug the path, inserted the 100-millmetre slotted pipe into the ground, and in-filled above it with limestone caprock then a layer of topsoil.
Stirlings to Coast Farmers project leader Philip Honey says early results from the West Cranbrook and Perillup sites are promising.
At the West Cranbrook site installed in 2021, normalised difference vegetation index (NDVI) imagery showed higher biomass over the piped areas, plant tiller counts were up to 30 per cent better in the drained areas, and root structure and plant health was better.
“It is absolutely fair to say that they worked exceptionally well,” he says. “There was a 1t/ha yield premium through drainage in 2021, which was a 99 percentile year for rain, with about 744mm for the year – compared to the average of 480mm – and 527mm of growing-season rainfall.”
Crops on drained soil yielded 3.2 to 3.29t/ha, compared with 2.21t/ha for the undrained trial in 2021.
Philip says the income boost from higher feed barley yields extrapolated to paddock level, even at median prices, would pay off the $14,000 a kilometre installation cost in 3.8 years. But the up-front cost remains a major stumbling block for many growers.
Some growers in the region spent $200,000 on subsurface drainage in 2022 and Philip says they will probably spend the same again this year because “they are confident that it works”.
He recommends that growers take a systems approach to managing waterlogging, using a combination of surface and subsurface drainage to bring down costs. “A lot of the farmers here are paying potentially $6000 to $7000 per kilometre just to get a grader to put a drain in,” he says. “If you buy a new farm with no drainage, it might not actually be that much more to get the pipes in, if you haven’t got anything already.”
As well as yield and installation costs, Philip says the project is considering a range of factors such as machinery productivity, fuel consumption, the cost of repairs and maintenance, and operator fatigue.
A second site at Perillup was installed in early 2022 and sown to canola.
Stirlings to Coast Farmers is collaborating with South Coast Natural Resource Management on a similar trial in the Esperance Port Zone.
No simple fix
There is no off-the-shelf solution that will fix every grower’s waterlogging problems, according to Tasmanian mixed farmer Greg Gibson, who also operated a drainage contracting business for five years.
“The biggest thing to do is look at each site individually and treat it individually,” Greg says. “Look at the site, come up with a plan, know what you can spend and have the plan in place. It could take you four or five years, but you can keep working on it over a period of time, so there’s not the big impost of spending a lot of money up-front or in one go.”
The Gibsons farm 730ha near Cressy, in the northern Midlands, producing vegetables, poppies, ryegrass and canola crops for seed, as well as vegetables and wheat, and trade up to 10,000 lambs a year.
After crunching the numbers with his father, Ross, about 15 years ago, Greg says they realised just how much waterlogging was costing them every year. Ross had started putting in tile drains in the 1980s but seeing the losses in black and white motivated them to do more. Greg embarked on a Nuffield scholarship in 2014 to research strategies for reducing waterlogging.
“We’ve done a little bit every year,” Greg says. “We ramped it up when I came home and put centre pivot irrigation in and we pushed the farm into a more intensively cropped property. It has taken us 15 years, and I haven’t finished yet, but it is sometimes better than actually buying another farm: fix the one you’ve got first.”
Deluge prompts fresh look at drainage program
Waterlogging is not new to Andrew and Sue Russell, who farm at Lilliput, south of Rutherglen in north-eastern Victoria, where average annual rainfall is about 580 millimetres.
Shareholders in a cropping enterprise, Lilliput Ag, and an affiliated farming and seed cleaning business, Baker Seed Co, the Russell family produce grain and oilseed crops and run 3000 first-cross ewes for trade or prime lambs.
Much of the 2500ha area they crop is relatively flat, traversed by natural waterways that flow only during wetter years, so Andrew uses surface drainage and a half-degree fall to slowly, steadily run excess water off his paddocks.
“We’re fairly proactive with our paddock drainage. It’s not perfect – it’s a working document for want of a better word,” he says. “We’re always looking to improve, and after 2016 and 2021 we realised we needed to kick our drainage works into gear again.”
But 2022 had different ideas, starting with a late January storm that dumped almost 240mm of rain. Crops were sown into a soil profile full of moisture and, despite lack of sunshine and cool temperatures, by late August they were on track to equal 2021’s excellent yields.
“We fed all of the crops, and really just primed ourselves for what we thought was going to be another potential bumper,” Andrew says. “August–September was really when it started to get pretty wet and that’s when the first considerable signs of waterlogging damage were starting to appear, which for us is normal in a wet year.”
After 2016 and 2021 we realised we needed to kick our drainage works into gear again.
What wasn’t normal was the record rainfall that followed in late September, October and November, and the extended flooding of the Ovens and Murray rivers that stalled water flow in local creeks instead of taking it away.
“We were out there with shovels, clearing drains, just trying to get water moving and trying to open up those waterways,” Andrew says. “Because they’ve been flooded, they’ve carried a lot of debris that we were clearing and, had we been able to get machinery on, we would have done any sort of drainage we possibly could to try and help get water off, but we physically couldn’t get machinery anywhere near it.”
Many of the crops did not recover from spending two or three weeks underwater. The worst-hit was canola, which lost half its potential yield of 3t/ha. By year’s end the Russells had tipped a record 1150mm from the rain gauge.
Determined to “very proactively mitigate” against waterlogging in future wet seasons, Andrew collected drone footage and NDVI imagery along with yield data to add to their understanding.
“We saw waterlogged areas that we’ve never seen before,” he says. “That was pretty confronting, to be honest ... It said to us that as much as we were on the ball with our drainage program, it’s something that we need to constantly maintain.
“A lot of our drainage still works very well, although we’re acutely aware now that we need to upgrade and continue to upgrade it. Last year was a real reminder for us to maintain things better than what we’ve done in the past.”
Applications for 2024 Nuffield scholarships close 9 June 2023. Grain growers or partners can apply for a GRDC sponsored position.