Exposed sandy soils are at greater risk of erosion, especially during low-rainfall years, but a new research project has found it is possible to both prevent and repair blowouts, even in a decile-one year.
A survey carried out as part of the project found erosion was more likely to occur in the second or third year of dry conditions and cost growers an average of $80,000 each.
Three-quarters of those surveyed had livestock and almost two-thirds identified a fear of making things worse as their greatest challenge in managing wind erosion.
The most-common methods of successfully reducing wind erosion included the use of no-till, early sowing, reseeding damaged areas, growing specific crop varieties, soil grading or levelling, and reducing stock numbers and feeding them in containment areas.
Peter and Nigel Baird work on their Wentworth, NSW, property. Photo: Chris McDonough
The survey found leaving paddocks prone to erosion out of production generally did not work.
The project was prompted by a run of late-season breaks, well-below-average rainfall and low spring rainfall in most of the Mallee districts across the southern region between 2017 and 2020.
It aimed to identify practical strategies and solutions for growers to protect their farms and safely rehabilitate land for crop production.
For 20 months from 2020 to 2022, eight growers in four regions of New South Wales, South Australia and Victoria were involved in monitoring 33 sites. They also implemented proactive rehabilitation strategies to improve both ground cover and soils.
Satellite imagery assessed changes in ground cover relative to targets since 2015, and showed that most sites with more than 50 per cent cover in September were much less likely to blow out if the following season was poor.
Growers who took part in the project include Brenton Schober, who continuously crops 5500 hectares at Moorook and 2000ha at Borrika, in SA, with sons Ben and Clarke.
Soil types vary from deep non-wetting sands to sandy loams and heavy flats, and shallow calcareous stony flats. Average annual rainfall is 310 millimetres at Moorook and 254mm at Borrika.
The Borrika property was severely eroded when they took it over, so the Schobers began a program of levelling and re-establishing cover over most of their sandy areas in 2018.
They found repairing and sowing paddocks in April worked well, although resowing has been necessary in dry years and seasons with a late break.
“The whole emphasis is to get it covered before the wind in spring,” Brenton says.
“Even patches the size of a ute, I’ve gone and resown it by hand with a rake and a bucket. You’ve got to keep at it. Once it’s blowing you’ve got all of summer when it’s open to the environment. So the whole idea is to get it covered, get it growing and hopefully it’s there for the following year.”
By 2020 the Schobers had achieved their aim, but some ground was still uneven, making sowing and harvest operations difficult.
Those areas were re-levelled in 2021, using a scraper and landplane, and a harrow dragged organic matter from the flats to boost topsoil fertility and microbial activity.
Compass barley was sown in mid-May at a seeding rate of 70 kilograms/ha with 75kg/ha of 19:13:9 fertiliser. Despite a very dry growing season with just 110mm of rain, the crop grew enough cover to remain level for harvest and the soil held across summer, allowing lupins to be sown into the stubble this year.
“We had a reasonably windy year and a dry year, a decile-one year, but it still managed to hold,” Brenton says.
“I was actually quite surprised; every time I came down to have a look I was expecting to see large, pink, bare hills as you come down the road, but they were green.”
Brenton says they will continue with the barley/lupin rotation to improve the soil. Sheep, which are notorious for camping on small bare areas and making them worse, are “banned for now”.
Handling drought
Combating erosion is much less straightforward for Nigel Baird, who runs a 45,000ha sheep station and crops 2000ha north of Wentworth, in far south-western NSW.
Soil types vary from deep sands to good fertile loam over clay, interspersed with poor-producing, highly erodible, marly loams, and average annual rainfall is 200mm.
There are few fences on the property and wildlife flourish along the Great Darling Anabranch – which winds its way south from Menindee to the Murray River – and a string of ephemeral lakes when they are filled by northern rains.
After above-average rainfall in 2016, drought set in during 2017, with just 60mm of growing-season rainfall hampering crop production and growth of native ground cover.
An influx of kangaroos, emus and feral goats consumed stubble and whatever vegetation they could find, exposing cropping paddocks that became lumpy and uneven in the two dry, windy years that followed.
Concerned about worsening the erosion risk, Nigel held off rehabilitation works until earlier this year, once subsoil moisture and pre-seeding rains were adequate.
It took numerous passes with a chisel plough and prickle chain, followed by many runs with a steel H-beam levelling bar.
“In these situations, you are 100 per cent committed,” he says. “As soon as you work the ground the first time, it’s all or nothing. There is no turning back.”
Once the last levelling passes were done, Nigel cross-sowed Grenade CL Plus wheat on 22 May at a seeding rate of 60kg/ha on the most vulnerable areas and gave it 60kg/ha of a MAP/SOA blend (27:12) to help maximise establishment.
The crop has grown well, and the paddock will not be grazed this summer.
Nigel hopes returning to his usual strategy of minimal grazing and no-till cropping will be enough to retain sufficient ground cover to protect the soil in future.
Allowing for stock feed
Mixed farmers Chris and Leanne Hunt closely monitor grazing paddocks at the family’s 5500ha farm at Merrinee, in the Millewa region of the Victorian Mallee.
The Hunts run 1000 Merino ewes, which they join to Poll Dorset and White Suffolk rams to produce first-cross sucker lambs.
Soil types range from loamy sand rises to good sandy loam flats, interspersed with less-productive marly sodic flats, which are prone to blowouts. Average annual rainfall is 280mm.
Stock containment areas and having feed on hand have been part of their strategy since 2018, allowing the Hunts the flexibility to pull sheep out of paddocks and retain 50 per cent anchored ground cover.
Chris says this is much safer than allowing paddock grazing, where the poor patches can become exposed and trigger significant erosion.
Having their own hay cutting and baling equipment allows for vetch and cereal hay to be stockpiled, and barley straw to be baled when hay is in short supply.
“Using our own hay and straw is much preferred over the risk of bringing unwanted weeds on to your property from outside sources,” Chris says.
As part of the three-year GRDC project ‘Practical tactics to improve ground cover and ensure soil preservation following successive low rainfall seasons’, Insight Extension for Agriculture farming systems consultant Chris McDonough is producing a series of case studies and reports with Mallee Sustainable Farming.
He says adoption of conservation farming techniques has dramatically reduced the frequency of wind erosion in the Mallee, but seasonal unpredictability still leaves the region’s sandy soils highly vulnerable.
“This project aims to provide practical strategies and solutions for growers within a range of farming systems and low-rainfall environments to best protect their farms from soil degradation and rehabilitate land safely back into production,” Mr McDonough says.
“These case studies will provide growers with easily accessible insights, improved benchmarks and strategies for overcoming these significant issues in very uncertain times.
“Even in the worst-case scenario, we found that some careful management could repair and re-cover the soil.”