Crops to get frostier reception

Last year, crippling August and October frosts cost farmers throughout southeastern Australia millions of dollars, while Western Australia has also had severe spring frost events in recent years.

The Grains Research and Development Corporation (GRDC) estimates frost causes losses of around $360 million per annum to Australia’s grain growers, and has set up the National Frost Initiative (NFI) to find ways of mitigating the problem.

Ben Biddulph of the NFI said the project had three key areas to explore: genetics, management and environmental prediction.

The first major outcome from the NFI has been the release of a frost susceptibility table, which comprises most of the widely grown lines of wheat in Australia.

A total of 72 wheat lines have been assessed through the Australian National Frost Program (ANFP), using a standardised set of measures to assess frost damage in the field, with the results now readily available on the National Variety Trial (NVT) website.

New plans against frost will be critical if the pattern of a widening frost window discovered by CSIRO continues.

CSIRO senior research scientist Steven Crimp said at the recent GRDC update in Ballarat, Victoria, that farmers had to manage a balancing act more difficult than ever, due to increased risk of both frost and spring heat stock.

“The start and the end of the frost season has expanded so we are getting much later frosts occurring,” Mr Crimp said.

“In the last decade the frost window has been 40 days longer than at the start of our records in the 1950s.”

The worst of the increases in frost are in eastern Australia, however, much of South Australia and Western Australia has long been particularly prone to damaging frost events, to the extent some growers in the SA Mallee will only grow hay crops in particularly frost-prone low lying paddocks.

The critical factor for crop damage is the fact the frosts generally occur in tandem with increasing daytime temperatures, meaning plants can be under more moisture stress than is normal, making them more vulnerable to frost damage.

CSIRO research scientist James Hunt has been testing time of sowing throughout Victoria to see whether there was a ‘sweet spot’ that mitigated both frost and heat risks.

“There has been a push to go earlier and earlier with time of sowing, but I think in 2015 we found the limits of that.

“Early sown crops had abundant water and were well ahead of average development at the end of July, which was why the frosts in early August caused so much crop damage.

Although last year’s early crop development was due to a unique combination of climatic factors, such as early rain and a mild May, studies are indicating wheat phenology is coming forward.

Mr Crimp quoted a figure of crops being roughly a week earlier for every degree warmer during the growing season.

Dr Hunt said farmers could exploit seasonal conditions with early sowing, but would have to closely consider their variety choices when doing so.

“There are opportunities for earlier sowing, with long season wheat lines if conditions suit, but otherwise, sowing within five to seven days of the listed optimum date is the best practice.”

He also highlighted the need for a range of varieties.

“It is impossible to predict when frost and heat events will occur so you have to spread your maturity dates.”

Further to that, he said diversification into totally different crops and even into other enterprises such as livestock was also sound risk management.

“Crops like oats and vetch are more tolerant of frost, so look at options like that if you are concerned about frost.”