IN his time as a consultant, Agrilink's Mick Faulkner said one of the most concerning changes he had seen was the extension and severity of the frost period.
"While the frost season has extended later, it is accompanied by an increase in late-August and early September. This extension is one of the biggest changes for frost I have seen in my time," he said.
"This period was once cloudy, breezy and raining, but it is no longer that.
"In recent times we are getting three - to five-day events that are really, really cold. It is also occurring more than once, creating a lot of stem frost damage. Many farmers are trying to maintain a productive farming system that is constrained by anthesis and grain filling frosts that have extended later into spring, as well as August and September frosts that either cause stem frost or play havoc with early maturity. With warmer and drier conditions over the last decade earlier maturity has helped maintain or increase productivity in the absence of frost but those who experience frost have become more exposed.
"When really cold conditions occur the damage hasn't been limited to flats, it's across a few different types of landscape."
Mr Faulkner was a guest speaker at last week's GRDC Grains Research Update in Adelaide, where he talked about agronomic options for frost mitigation.
We need to map paddocks into red, yellow and green zones, and adjust management strategies accordingly.
First, farmers needed to identify susceptibility zones across paddocks, and in the bigger picture, across their farms.
"We need to map paddocks into red, yellow and green zones, and adjust management strategies accordingly," he said.
"As Vera Nazarian once said: 'The cactus thrives in the desert, while the fern thrives in the wetland. The fool will try to plant them in the same flowerbox'.
"That's exactly where we are at the moment and this needs to change."
Mr Faulkner said green zones were areas never affected by frost, often because of innately warmer conditions, sea breezes or katabatic winds.
In these areas, farmers could generally "just go for it" with a high-yield strategy, which included continuous cropping, high-value crops, soil maintenance or improvement and stubble retention.
While in red zones, where frosts were severe or frequent, Mr Faulkner said there were few opportunities to retain stubble, grow varieties and maintain farming practices that were so successful in the green zone.
"Even if you do jag a good year in the red zone, and high stubble loads are left behind, the temperature change, as a result of the stubble itself, can be pronounced and planting another cereal can result in major losses to frost," he said.
Playing with high stubble stubble loads in a red zone, is playing with fire.
"The only way to get a change in temperature is to either darken the soil and increase the surface layer density, by adding something like clay for light soils or removing the stubble.
"Keep the stubble for as long possible to get all the moisture and other benefits over autumn, but then reduce it.
"I'm not saying to always burn in the red zone as there are options, including discing, rolling, straw removal or fencing it off so sheep graze the area better.
"Playing with high stubble stubble loads in a red zone, is playing with fire."
For red zones, Mr Faulkner advised refencing for livestock or pasture use, haymaking, incorporating or removing stubbles, rolling the zone after seeding, maximising biomass and not growing susceptible pulses.
"Alternative strategies to maintain soil cover for as long as possible and the addition of organic amendments from off farm rather than leave large amounts of surface stubble should be investigated," he said.
Mr Faulkner said sowing faba beans really early could work.
"This may fly in the face of growing faba beans in the green zone where excess early vigour can reduce yield and provide ideal conditions for fungal disease," he said.
"Faba beans have proven to be more resilient because the flowers and small pods can gain some protection provided by the canopy above them and pod walls are quite thick as they mature, providing a bit more insulation to the beans inside.
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"A big canopy might mean a bit more resilience for frost.
"A past strategy for cereals might have been to sow later but there is more to be gained by sowing long-season varieties early; a mix across the farm of winter (vernalisation requiring) and photoperiod (responsive to daylength) in the red and yellow zones and sowing the temperature-sensitive varieties into the green zones.
"A new look based on some good research many years ago is to mix the varietal physiology and phenology in the same paddock, and a possibility is by using something like intercropping. This approach may create enough varietal maturity difference and some pretty neat microclimate changes to reduce damage to acceptable levels."
Mr Faulkner said limited trials showed intercropping produced greater stability than maybe a tank mix of the same varieties or just one of the varieties in each paddock, in the absence of frost.
"It now needs to be tested in yellow and red zones to determine if there is merit in this type of approach," he said.
"The undulating canopy can create tiny eddies which may increase ambient temperature by 0.5 degrees, which may be in the same order that varietal differences have provided."
DIVERSITY KEY TO REDUCING SUSCEPTIBILITY
AGRILINK consultant Mick Faulkner also outlined the middle, yellow zone, which is not consistent in temperature and damage from one frost to another and between years.
"In some years the yellow zone is large and can best be mapped in the really bad frost years," he said.
"However, in other years when frosts have a more benign impact the yellow zone may be quite small and retreat closer to the red zone.
"The distinguishing feature of the yellow zone is that its size and degree of damage is inconsistent, and that there are no predictive weather and climate tools that have been successful in defining it prior to sowing."
Mixing up varieties, intercropping, growing pastures, rolling paddocks in case they need to be cut for hay or grazing to reduce stubble loads are all relevant tactics for this zone, but dual-purpose crops, particularly awnless varieties could also be considered.
"Dual-purpose crops in this context are those that provide an option of either late-season grazing, hay or grain, depending on frost," he said.
"The decision on the use of the crop isn't made until the critical stages in spring rather than at seeding.
"The only issue is there aren't a lot of options to choose from and some varieties are not well adapted to SA environments."
But Mr Faulkner said there were awnless cereals out there and they are yellow and red zone options.
When asked about optimal flowering windows, Mr Faulkner said it was a very relevant green zone concept, "iffy" in the yellow zone and of limited value in the red zone.
"Identifying an optimum flowering window in the red zone is difficult because we don't know when frosts are going to occur or how severe they will be," he said.
"In the red zone, it's about diversity of reproduction and grain filling so there is at least something that avoids or is not susceptible to stem frost, as well as avoiding reproductive and grain filling times, in the mix.
"It is unlikely that all frost damage can be avoided but reducing the impact to an acceptable level is highly desirable."
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Mr Faulkner said early sowing was beneficial to all zones, generally from April to May 1 but success in the green zone could be disaster in the red zone.
"Wheat varieties such as Scepter, Vixen and Trojan invariably perform very well in the green zone when sown early to mid May but they are extremely high risk in the yellow zone and not suited to the red zone at this time," he said.
"April and early May sowing in the yellow and red zones should be pursued, but it means a change in variety and what temperature cues they respond to.
"Sown on May 1, a temperature sensitive variety like Scepter stacked up pretty well when there was no frost (ie in the green zone) but was a disaster in the red zone.
"When sown on May 15 it was still severely frosted in the red zone. And even sowing on May 24 meant it still had high losses from frost."
Mr Faulkner said there was a huge opportunity for early sowing in the red zone, but the drivers of maturity would require variety change incorporating some vernalisation and photoperiod sensitive cereals.
"There are some possible interventions to change the maturity of a variety once it is growing, but there has been little research, other than grazing," he said.
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