South Australian grain growers faced devastating frost damage in 2024, prompting experts to emphasise the importance of frost management strategies for the 2025 growing season.

EPAG Research Trust director and research agronomist Andrew Ware addresses a session at the GRDC Tooligie Frost Tactics trial site in September 2023. Photos: Supplied

The 2024 growing season dealt a severe blow to South Australian grain growers when frequent, widespread frost events severely damaged crops, many already struggling in the dry conditions.

The experience has raised awareness of the need for growers to manage frost-prone areas differently by drawing on well-researched mitigation strategies.

The timing could not have been worse for growers on the Eyre Peninsula (EP) and in the state’s Mid North, where frost events in September and October hit before, during and after flowering. EPAG Research Trust director and research agronomist Andrew Ware says a late season break had forced many growers to dry sow. Then, crops received only around Decile 1 growing season rainfall (GSR).

The Wudinna airport weather station recorded GSR of just 137.8 millimetres, and 187.6mm for the year. This compares with an annual average of 272.7mm.

There were also five days below zero in mid-September. In some parts of the EP, temperatures dropped as low as minus 6.5°C.

“Just about everything was flowering at about the same stage, so there wasn’t much diversity in the way the crops were developing right across the peninsula,” Mr Ware says.

“When we had that week or so of cold weather in September, it really sorted a few things out.”

The main crops affected were lentils and wheat, although significant damage also was reported in canola and barley.

Mr Ware says growers had been slow to accept frost-prone areas needed to be managed differently, but this was changing with frost events now occurring from July through to the end of October.

In some years, he notes, it does not matter when your crop is flowering, you are still going to get hit with a frost in the really bad areas, so expectations for these zones need to be managed differently.

Eyre Peninsula independent consultants working on the Frost Tactics project (from left) Josh Hollitt (Hollitt Consulting), Andrew Ware (EPAG Research), George Pedler (George Pedler Agronomy), Andy Bates (Bates Ag), Michael Hind (Bates Ag) and Ed Hunt (Ed Hunt Consulting).

Preparing for 2025: Lessons and strategies

Zones are a concept conceived by Agrilink Agricultural Consultants principal Mick Faulkner, who divides paddocks into three zones: green, amber and red.

In addition to using zones within paddocks, the overall impact on farm profitability is determined by the relative areas of green, amber and red zones.

Green zones never experience frost damage, red have severe financial impact from frost, and amber are areas that have some frost risk, depending on the severity of individual frost events.

Zones can be identified by field scouting after frost, confirmed by using contour and yield maps, and using knowledge of soil type, landscape and previous generations who have experienced many frosts.

Mr Faulkner recommends zones become a permanent part of the farm management plan.

“[Growers] need to treat a red zone quite differently to the green zone because cumulative profitability will be quite different, due entirely to frost,” he says.

“In addition, as a grower, I don’t know when I’m going to get damaging frosts, so just doing the same thing everywhere either increases risk in the red zone or reduces profitability in the green zone.

“There is no way a red zone can be more profitable than a green zone. Ever.”

Mr Faulkner says agronomists and advisers also need to understand and think differently about crop types and inputs when they go from a property with a small red zone to a property with a big red zone, which requires a more conservative approach.

“The impact on the business for someone who has 30 per cent of their property as a red zone is far different to someone who’s got five per cent of their property as a red zone.”

What researchers are doing

There is some debate over whether damaging frosts are becoming more frequent with climate change, but there is no doubt they are becoming more intense, according to Mr Faulkner.

And the losses are mounting. Frost damage is costing wheat producers alone an estimated $400 million a year.

Mr Faulkner, who has been involved in frost research for many years, says that while it is common to attribute frost damage to a single event, in reality it can be due to many individual freezing episodes.

“In 2024, for instance, it is convenient to suggest that the frost of 18 September [at his research site at Farrell Flat, east of Clare] was responsible for all the damage because air temperature at canopy height reached minus 8.2°C.

“However, four of the previous five nights had frost at temperatures below 4°C, as did the night after and eight nights later.”

After a run of bad frosts across large areas of the EP from 2017 to 2021, Agricultural Innovation & Research Eyre Peninsula Inc (AIR EP) established a demonstration site at Tooligie Hill to evaluate tactics for better managing frost.

Led by Mr Ware and with guidance from frost researchers, including Mr Faulkner, the two-year project investigated varietal phenology and sowing time, growing mixtures of varieties with differing maturity, the use of nutritional and ice-nucleating bacteria products, zoning and the role of soil amelioration.

It found high-risk areas could experience more than 30 frost events from June to October, making it difficult to avoid frost through variety maturity and time of sowing, although there was value in being able to identify zones of high frost risk and manage them differently.

The project also demonstrated canopy temperatures were 0.5°C to 1.0°C warmer during frost events in sandy soils that had been ameliorated, but products claiming to improve crop resilience to frost showed no yield benefit.

In-season manipulation

Field Applied Research (FAR) Australia research manager Max Bloomfield says the 2024 spring frosts also affected wheat, barley and canola crops in the Victorian Mallee and Western Districts, and southern NSW.

“It’s a balance between frost risk on one side and heat and drought risk on the other,” he says.

“And with the changing climate, we see frost events later in the season a bit more often than we’ve seen historically.”

Mr Bloomfield is leading a project to assess the potential for dodging frost damage by in-season manipulation of crops that are developing too quickly.

One method trialled to delay flowering time has been mechanical defoliation with a mower to simulate grazing of early sown Vixen and Scepter wheat, and Rosalind , Spartacus CL and RGT Planet barley.

“We’ve found the defoliation method hasn’t been a substitute for a better variety or a slower-developing variety, but nonetheless we’ve found that we can delay the flowering time of the quicker-developing wheat and barley varieties and increase the grain yield, or at least keep it similar to what it would be if we had done nothing.”

Canola has been a different story, with defoliation causing yield penalties even though it successfully delayed flowering.

Based on WA research into ice-nucleating bacteria, which fall into crops with rain and allow plants to freeze at higher-than-usual temperatures, Mr Bloomfield says they are also testing bactericides and cryo protection products.

“This is all still quite experimental,” he says. “In our
field trials there hasn’t been really bad frost over the last two years for the sites we’ve had these trials at, but the lab results are showing that we’ve been getting some control of the ice-nucleating bacteria.”

GRDC has put more than $20 million into frost research
during the past 25 years, including the five-year National Frost
Initiative that investigated genetics, management and environmental prediction using farm-scale maps, and several projects funded through the GRDC National Grower Network.

GRDC also launched three investments in 2024 – collectively valued at $10 million – into methods of reducing the impact of spring frosts on wheat yields.

Post-defoliation using a mower to simulate grazing of wheat and barley at the Field Applied Research Australia trial site at Salmon Gums, WA, in May 2024. 

What growers can do to manage for frost

• Identify and map red, amber and green zones to determine the actual financial risk due to frost.
• Have a strategy of avoidance, tolerance and mitigation that is appropriate for red and amber zones – do not reduce profitability on green zones.
• Make better use of existing tools such as yield maps, which can help identify frost-prone areas and convert them into zones.
• Ameliorate sandy soils, which cool quickly overnight and are more prone to frost.
  Deeper cultivation can help lift canopy temperatures during frost events. Amelioration is one of the few tools growers have to change how much land is in each zone, and can help to convert a red or amber zone to a green zone.
• Consider alternative crops or less-susceptible varieties for high-risk areas. These include barley, vetch for hay or a
  long-season woolly pod vetch for grain.
• If trying to avoid frosts by choosing later-maturity varieties, it may be better to sow a photoperiod or vernalisation-sensitive variety early rather than later sowing of the variety that performs best in a green zone.
• Consider dual-purpose crops, such as the awnless wheat varieties Bale^A, Dual^A and DS Bennett^A. These varieties might have lower grain yields depending on the season but produce more biomass and can be grazed or cut for hay if domestic or export markets are accessible. They should not be grown in green zones but have a strong fit in red zones.