New research has confirmed changes to frost patterns in the Western Australia grainbelt, with frosts occurring later in the year and therefore increasing the risk of damage to maturing grain crops.
The research conducted by CSIRO and funded by the Grains Research and Development Corporation (GRDC) found that in the last 30 to 40 years, 'frost window' start and end dates had been pushed back by between one and four weeks across many WA cropping areas.
CSIRO researcher Steven Crimp said this was in contrast with the eastern states where the window had broadened by up to six weeks, with frosts starting earlier as well as finishing later.
“Much of the change in the number of frost events in WA and other Australian cropping areas has occurred in the months of August and September and during the last two decades,” he said.
“The results show that farmers’ exposure to frost risk has changed and that they may require enhanced frost mitigation strategies to minimise the chance of damage to grain crops in spring.
Crimp said the ‘Understanding frost risk in a variable and changing climate’ research project had also revealed that severe frost events in WA were more likely to occur when centres of ‘ridging high pressure systems’ were farther south.
“In WA, 83 percent of frosts from September to November occurred when high pressure systems were situated south of 35S and between about 108E and 110E,” he said.
“Another finding was that there has been an increase in the number of consecutive frost events, with WA, much of Victoria and South Australia showing a mean increase of up to six consecutive days with minimum temperatures at or below 2 degrees Celsius.”
Crimp said that, where possible, growers should change their exposure to frost risk.
“At the same time that there have been changes to frost patterns, there has also been a warming climate, which tends to shorten the growing season and bring crops, in terms of their flowering, back into periods of higher risk,” he said.
“This quicker phenology, combined with a higher likelihood of frost late in the growing season, contributes to a significant increase in the risk of frost damage to crops.
“Time of sowing and variety selection are key factors that may provide some benefit in managing frost risk.”
Crimp said the research could lead to the development of a frost forecasting tool, ultimately helping growers to make better cropping decisions.
The GRDC has invested more than $13.5 million into frost-specific projects since 2000.
It has invested an additional $43.3 million into projects aimed at delivering data and tools needed by growers to manage the impact of frost, such as variety specific agronomic information, online sowing time tools and improved long-range frost forecasting capacity.