GROWING multiple varieties of a crop within the same paddock may be a solid frost management tool for grain producers.
South Australian consultant Mick Faulkner, Agrilink, based at Watervale in the Clare Valley, said trial data had showed good results in paddocks planted with multiple varieties.
"The mixed paddocks were constantly around the median," he told the crowd at the recent Grains Research and Development Corporation update in Adelaide.
"The best yields belonged to varieties that missed the worst of the frost damage due to being later flowering and the worst damage was to the earlier maturing crops, however at the start of the year you don't know when that damage will occur so the mixed approach is a method of avoiding that real wipe-out," he said.
Andy Barr, who farms at Pinery, in South Australia's lower Mid North, said he had been trialling mixed variety plantings in both wheat and lentils with some success.
"I mix an early maturing variety, such as Vixen, with something later season and the difference of flowering dates mean you are not exposed to one wipe-out frost event," Professor Barr said.
"Over time we've managed to eliminate those peaks and troughs you see with frost damage, you don't get the very highest yielding crop but more importantly you don't get the worst, and given you don't know when the frost will hit that is important."
Logistically, Prof Barr said the variety mixes did not present any problems.
"The timing of flowering is quite spread out but due to the way the wheat plant matures the gap between the varieties narrows significantly at ripening."
"Given wheat normally is harvested after other crops, such as barley and canola, I've had no issues with uneven ripeness at harvest."
Quality-wise, Prof Barr said the mix always featured two varieties of a similar quality profile.
"There has not been any problem with segregation of the grain."
Prof Barr said he planted the mix across his entire farm, saying there was the risk of frost in all areas, however Mr Faulkner said if farmers had areas that were not frost-prone they did not need to implement a frost management strategy.
"Frost risk management almost always means reducing income in non-frost areas, that is why it is important to get a handle of where the risk is."
Mr Faulkner said he worked on areas of high loss, which he dubbed red zones and areas that rarely had issues, green zones with amber zones in between.
"The idea is to minimise those losses in the red zones while maximising returns in the green zones."
"It is critical to get an idea of where your farm sits via things like topography mapping and yield mapping - some farms will virtually all be in green zones and not need too much in the way of a frost management strategy while others will have a lot of red zone area and will need to work on plans to minimise risk."
Along with varietal mixes Mr Faulkner said farmers could work to push their crops outside the frost risk window.
"This could mean you still plant your favoured early variety but intervene in plant development with something like livestock grazing to delay growth so it is not in a susceptible stage in the frost window."
However, he said the difficulties with this were that the frost window extends so long towards the end of the season, well into November in South Australia.
Crop choice was another means of limiting damage.
Research has showed that oats, reflecting their heritage in cold areas of northern Europe, are the least susceptible crop to frost, making them a solid option in frost prone paddocks or zones.
Planting a dual purpose variety that can make good quality hay is another option to allow farmers to pivot in the event of a severe frost event.
Mr Faulkner said there were still a lot of things to learn about frost.
"In spite of the commonly held belief the correlation between frost damage and temperature is relatively low."
"Obviously above a certain temperature there will be no damage and below a very cold temperature there will be complete desiccation, but within the extremes things like plant physiology and ice nucleation play a bigger role than the temperature itself."
Mr Faulkner said instead of temperature it was bacteria, which impact on ice nucleation, that were the biggest driver of frost damage.