Fiona Hobley (pictured with a Tiny Tag temperature logger) has tested the effects of different stubble loads on frost damage south of Nyabing, Western Australia.
PHOTO: Nicole Baxter
Frost events are difficult to predict and frost damage can be hard to assess, presenting growers with the double challenge of how to minimise exposure and then manage any impact on crops. While there is no silver bullet to this frosty problem, growers and advisers at the GRDC Grains Research Update in Adelaide were given a list of prevention and management strategies.
Preventing frost damage
As CSIRO researcher Dr James Hunt explained, the severe and widespread frost that hit many crops in southern Australia in October 2014 was unusual; however, it could be a sign of things to come.
“We can’t rule out the possibility of this sort of event happening again so it’s valuable to assess the timing and variety of crops planted,” he said. “Understanding how the varieties you sow progress through their development can make a huge difference to frost vulnerability. Varieties are getting faster and the time of sowing is becoming earlier, which is exposing crops to frost risk.
“Growers in high-frost-risk areas should look at slower-maturing varieties if they want to start sowing at the end of April. Matching species (oats and barley are more frost tolerant than wheat) and enterprises (cropping, hay or livestock) to frost zones on your farm can also help mitigate the impact of a frost.”
Dr Peter Hayman, from the South Australian Research and Development Institute, said damaging spring frosts are relatively rare events.
“Frosts are high-consequence, low-frequency events, which makes them very hard to get knowledge about, hard to predict and hard to manage,” Dr Hayman explained. “Anything growers can do to store radiation from the day before and minimise outgoing radiation during a frost event is going to benefit their crop.”
The GRDC is funding research to better understand the weather conditions that lead up to frosts and to see if there is any chance of predicting changes in the likelihood of frost in the coming season.
Dr Tim March, from the University of Adelaide, gave an update on the GRDC National Frost Initiative, a five-year program that aims to deliver growers a combination of genetic and management solutions, plus tools and information to better predict frost events.
He said the new frost rating system – produced through the National Frost Initiative and to be available on the National Variety Trials website later this year – paves the way for pre-emptive action when deciding which varieties to sow.
“Frost susceptibility varies between varieties, but it is important to firstly select varieties based on your environment and production goals, then use the frost rating to fine-tune risk management,” he said.
Jeff Braun, from Agrilink, encouraged growers to create a well-stocked frost toolbox.
“Keep good paddock records and use yield maps from years where frost damage occurred overlayed with elevation maps to identify frost-prone areas in paddocks. Temperature loggers are useful for improved frost monitoring.
“Planning is important. The time of sowing should balance maximum yield against the risk of frost and heat shock. Don’t include frost-risk areas for forward marketing, and roll paddocks or areas of paddocks with a frost risk after sowing so that the paddock is prepared for making hay, just in case.”
Managing a frosted crop
An accurate assessment of frost damage will guide crop management.
Andrew Parkinson, from Landmark, said he advises growers to look for damage by checking stems for lightened or softened areas a minimum of five days, preferably seven to 10 days, after a frost event. He suggested checking heavy straw patches as bare ground radiates more heat, and not only looking in low areas as frost is now occurring higher up rises than was traditionally seen.
“There are three main options for a frosted crop,” Mr Parkinson said. “Leave it to harvest as grain, cut and bale it for hay, or graze the frosted areas. The right option for each farm business depends on equipment, infrastructure and, of course, budget.”
- Leave: If the frost is prior to GS31 to GS32, most cereals can produce new tillers to compensate for damaged plants. Pulses and canola also should still have time to produce more growth. A later frost is more concerning, especially for crops such as wheat and barley as there is no time for compensatory growth. Faba beans, which flower and pod over an extended period of time, should be less affected.
- Cut and bale: This is an option when late frosts occur during flowering and through grain fill. Assess crops for hay quality and be prepared to cut more than less as yield will be reduced.
- Grazing: An option after a late frost when there is little or no chance of plant recovery, or when hay is not an option because of farm set-up or limited marketing opportunities. Spray-topping may be incorporated, especially if the paddock will be sown to crop the next year.
For growers who chose to go down the grazing path, Hamish Dickson of AgriPartner Consulting said it pays to be prepared.
“Grazing frosted crop can be highly profitable, but it can require investment, logistics and infrastructure, so it may not be a frost-management option for everyone,” Mr Dickson said.
The decisions to make when it comes to using frosted crop as stockfeed are as follows.
- Will the frosted crop be used as on-farm hay? Different classes of stock (lactating, dry, young) have different nutritional requirements. Conduct a feed test to assess hay quality.
- Will the crop be grazed? Ensure there is appropriate fencing/water infrastructure (permanent or temporary) for the selected livestock.
- Is spray-topping required? Spray-topping is an effective way to store feed as a resource through summer, but is not necessary if grazing immediately.
- What are the risks? If there is a greater chance of grain recovery from the standing crop, be mindful of acidosis (especially when grazing wheat) and pulpy kidney.
- Are there other budgetary considerations? Consider the cost of buying-in livestock and supplementary feeding, if required.