SOWING a ‘shandy’ mix of different wheat varieties into the same paddock could buffer crops against the risk of frost and heat damage later in the season.
CSIRO farming system scientist, Dr Andrew Fletcher, Perth, said trials over three years in Western Australia had shown that wheat variety mixtures containing genotypes with varying phenologies could mitigate the risks of frost, heat and drought stress and help stabilise yields.
Speaking at the 18th Australian Agronomy Conference in Ballarat, Victoria, this week, Dr Fletcher said the research sought to overcome the dilemma farmers faced about what was the right sowing date and the right variety to manage the dual risks of heat and frost.
“If the crop flowers too early you put yourself at risk of frost, but equally if it flowers too late you put yourself at the risk of heat. But, you don’t know at the start of the season which of those it is going to be an issue and what the right sowing dates are,” he said.
“So, we did an experiment with commercial varieties of different duration. Instead of just planting them as single varieties we put them in as a mixture, the idea being you spread the risk.”
The trials were conducted using three varieties: Yitpi (long-season), Mace (mid-season) and Tammarin Rock (short-season).
There were several treatments that were combinations of two-way mixtures and one that had all three.
In 2015, they were sown on 8 May (early-sowing), 23 May (mid-sowing) and 2 Jun (late-sowing) at Brookton, WA, to expose the crops to varying degrees of frost around flowering and heat stress during grain filling.
“We planted across three sowing dates to try to get one that was at risk of frost, one that was somewhere in the middle, and one that was at risk of heat,” Dr Fletcher said.
“What we found was that, in Western Australia, the mid-maturing one, Mace, and the longer maturing one, Yitpi, seemed to be a good mix.
“Across all three sowing dates, the Yitpi/Mace mix was the highest yielding, or no different to the highest yielding one.
“From the earlier sowings, Mace was a bit too early on its own. It was lower than Yitpi. But at the later sowings, Yitpi was too long. So, the Yitpi/Mace mixture seemed to go really well across all the sowing dates.”
Dr Fletcher said the results were particularly relevant to paddocks that were low in the landscape and frequently impacted by frost.
“I reckon if you are in a frost-prone environment it is worth considering growing one of these ‘shandies’, particularly in a frost-prone paddock that would otherwise yield quite well, but you end up leaving it to last to sow, thereby compromising its yield,” he said.
“Quite often some of the frost-prone paddocks can have good soil and everything else set up nicely, but because it is frost-prone people sow it last and therefore compromise yield on it.
“We think this will give farmers more confidence they can sow paddocks like that earlier by spreading out the risk.”
Dr Fletcher said one of the main challenges for farmers adopting such a strategy was to find varieties that had the same delivery specification and to make sure they could be delivered in the same bin.
“There is also a question around end point royalties. When you deliver it you have to say what variety it is,” he said.
“The other part is the management side of it. The varieties we chose were contrasting, but they weren’t ripening a month apart or anything like that. But, if you have two very different varieties you might end up having to spray them at different times.”