A comprehensive manual to identify, evaluate and manage constraints in sandy soils is a key output of a project that will now be extended to amplify the benefits of amelioration – benefits starkly demonstrated in a dry 2024 growing season

Research to increase productivity in sandy soils constrained by water repellence, high soil strength, infertility and low pH is underway across South Australia and Victoria.

Sandy Soils II builds on an initial GRDC Sandy Soils investment that wound up in 2023 after six years of research across South Australia, Victoria and New South Wales.

The new project will look at:

• where, for the best outcomes, to start and stop deep tillage according to soil type;
• when to ameliorate by understanding the longevity of responses to amelioration;
• how to push and feed ameliorated sands to increase yields sustainably; and
• how to best manage agronomic practices and crops post-amelioration.

The investment will refine lessons and advance knowledge gained from the first project, which focused on three main themes:

• understanding the physical and chemical constraints of your sandy soil;
• identifying the relevant tools and treatments to address these constraints including amelioration (deep tillage) solutions; and
• evaluating the costs, returns and benefits associated with amelioration.

The GRDC technical manual Sandy Soils of the Southern Region provides a one-stop-shop of the project’s findings to support evidence-based decision-making around amelioration and improving sandy soils through deep tillage.

Benefits in dry season

CSIRO research team leader Dr Therese McBeath, who is the coordinator of both projects, says the benefits of soil amelioration were evident in season 2024, which was marked by a late start, frost and decile 1 in-season rainfall across SA.

The project’s trial sites from the Eyre Peninsula to the South Australian and Victorian Mallee found biomass – correlating to grain yield – was double in soils that were freshly ameliorated compared with those untreated.

Plots were either ripped, mixed or inverted depending on the primary constraint identified – be it water repellence, acidity, compaction or low nutrient fertility. While the findings were positive, Dr McBeath notes that the strong crop performance could reduce the soil moisture profile for the coming season.

The trials, which will run for at least another three years, will provide the opportunity to assess these types of impacts. “We’ll be able to check for the risk of drying the profile down if there is an extended drought the next year,” she says.

Strategic deep tillage

The initial GRDC investment began in 2016 after grower surveys showed interest in increasing productivity on marginal soil types.

Supported by advances in machinery capability, the project has looked at how to use deep tillage strategically in sandy soils to drive productivity while supporting sustainability goals through the subsequent increase in biomass production and stubble retention.

In an important departure from past tillage practices, deep ripping in these systems does not replace minimal tillage systems, but rather works with it and promotes it, Dr McBeath says.

“This is tillage for the preservation of stubble retention, which sounds counterintuitive but can be achieved because it’s not frequent,” she says. “It’s a strategic amelioration intervention designed to be applied no more than every five to seven years to try to overcome a major constraint to plant root access to water and nutrients by strategically improving the soil profile.”

Table 1: The right management for your constraint.

Source: Sandy Soils II project

Adoption on-farm

Data gathered in the wake of the first project shows the research has supported significant adoption of strategic amelioration, with growers expecting to more than double the sandy area of cropping land that receives strategic tillage.

The new project is intended to further inform adoption by refining where in the landscape amelioration is best suited. It will also build understanding on how to push the system and minimise risk.

The big risks are tilling in the wrong soil type, which can cause erosion, or bringing up too much clay in heavy soil types,” Dr McBeath says.

“If you bring up too much clay in a low-rainfall environment, you’re changing your bucket. And in a drought that can result in the clay holding water that the crop can’t access.”

The project is also looking to deepen knowledge around tactical agronomy for such practices as seeding and inputs post-amelioration to sustainably support a system with higher yield potential.

We want to help underpin a system that spins up so it becomes more productive, but also sustaining.

“That means, for example, ensuring there is the correct fertility sitting behind plants that are accessing more water as a result of amelioration.”

A set of guidelines around best practice will be developed from the research to further support implementation on-farm, she says.

“As adoption is taking off, we want to make sure we’re on top of all the little tweaks you need to make to the agronomy and the system work.”

Breaking the boom-bust cycle

Involving some 30 researchers plus 20 partnering growers and agronomists, the first GRDC investment involved trials across 34 sites in SA and Victoria.

In September 2024 at Wharminda, SA, a Sandy Soils II project trial site characterised by water repellence, high soil strength and poor nutrition shows the difference in barley biomass in plots with ripping plus spading (left) and untreated. Photo: Brett Masters, EPAG Research

In 2024, five new research sites have been established at Walpeup, Copeville, Crystal Brook, Bute and Wharminda, and there will be post-amelioration assessments at existing sites at Coomandook and Mount Damper.

Partners in both projects include CSIRO, the University of South Australia, the South Australian Research and Development Institute, the University of Sydney, Frontier Farming Systems, Trengove Consulting, EPAG Research and Soil Function Consulting.

Dr McBeath says the aim is to provide definitive advice to support amelioration practices that enhance long-term sustainability and profitability.

“The Sandy Soils investment has achieved and will continue to support more consistent, sustainable outcomes by providing advice that will help avoid the boom-and-bust cycles associated with deep tillage of the past,” she says.

“It’s exciting to increase production, but there’s a risk with amelioration, so we’re helping to provide the evidence for where and when it’s appropriate and how you set it up to get the most out of it.”

In July 2025, the Global Conference on Sandy Soils will be held in Perth. GRDC is a major sponsor and more information can be found on the Global Conference on Sandy Soils website.

More information: Therese McBeath, therese.mcbeath@csiro.au

Resources

Learn more in Sandy Soils of the Southern Region.