Why a risk-management approach to frost is necessary

"The severe frost damage experienced in 2017 is a low frequency but high consequence event," said climate scientist Peter Hayman.
"The severe frost damage experienced in 2017 is a low frequency but high consequence event," said climate scientist Peter Hayman.

With frost damage estimated to cost the Australian grains industry over $300 million every year, understanding and managing frost risk was one of the key topics at the GRDC’s Grains Research Update in Goondiwindi last week.

Following severe frost damage across the northern grains region in 2017, South Australian Research and Development Institute (SARDI) climate scientist Peter Hayman presented an analysis of frosts in the region and the need for a risk-management approach.

“The 2017 season will be remembered for the widespread and frequent frost events across the northern GRDC region,” Mr Hayman said.

“And we need to learn from this damaging, but relatively rare sequence of events.”

In highlighting the best approach to managing frost risk, Mr Hayman said strategic pre-season planning, tactical adjustments at sowing time, responding to frost forecast within the season, responding to a frost, and post-season evaluation were all key to acknowledging that frost is not an issue that can be simply solved or removed from grain farms.

“Rather it is something that has to be lived with and managed,” he said.

“In addition to the direct damage from frost, there is an indirect effect from conservative sowing time/flowering time strategies to avoid frost. 

“This is captured in the statement in the 1970s by the pioneer of frost research at Tamworth, Dr Bill Single, that the fear of frost does more damage than frost itself.

“Local advisers and growers will have their own views on whether this still remains the case, but some recent modelling research indicates that this indirect cost is greatest in the northern region with the region suffering not only the greatest direct impact of frost, but also the greatest impact from strategies to avoid frost.”

Unfortunately, frost was not the only climate concern for grain growers in the northern region in 2017 with a dryer-than-normal winter followed by extremely high temperatures severely impacting yields.

“While it is useful to focus on the unique aspects of frost risk, it is important to consider the interaction between frost, heat, and water,” Mr Hayman said.

“Although Queensland and northern NSW had a wet October, most of the region experienced rainfall in the lowest decile for the six months from April to September.

“This was followed by the second half of September being extremely hot, with NSW recording the hottest days since records were kept in 1911 on September 23.

“Across the grain growing regions of northern NSW and southern Queensland the mean maximum temperature for the week ending September 28 was eight to 12 degrees above average. 

“Experienced agronomists will point to difficulties in separating the impact of frost from drought and heat on final wheat yield.

“Not only is thinking about the trifecta of frost, heat and water stress important when diagnosing and attributing damage to frost in a year like 2017, this model shows that it is essential when managing frost, and the interaction of frost with heat and water stress is a good reason for a risk management approach to frost.”​