CSIRO researcher James Hunt has said farmers in Australia’s medium rainfall zones (375-500mm) can benefit from using long season varieties and planting early.
Based in Canberra, Dr Hunt said varieties such as Bolac and Eaglehawk had merit in areas such as the eastern Riverina around Wagga Wagga, the Yorke Peninsula in SA and Victoria’s Wimmera.
“We’ve been conducting trials over several years, focusing on water use efficiency, and the results have been startling in certain areas,” Dr Hunt said.
Dr Hunt said the experiment with long season wheat varieties was conducted in high, medium and low rainfall zones.
He said provided the wheat was sown on time, there were good yield advantages.
Further to this, perceived issues with screenings were not a problem if the varieties were allowed to ripen prior to it getting too hot in November.
Dr Hunt said farmers David and Charles Kingston, at The Rock, near Wagga, yielded 4t/ha with Bolac, compared to district averages of about 3t/ha.
“I reckon there is real scope for farmers in the medium rainfall zone to plant long season varieties, planted in early to mid April,” Dr Hunt said.
He said in low rainfall zones, the need for shorter growing seasons due to variable springs meant they were not as well suited, but in the medium and high rainfall zones he said there was a good fit for the varieties.
Dr Hunt said the fit for early sown varieties was especially good when there was a good bank of moisture, such as after a year with heavy summer rain.
“At this stage, it doesn’t look there will be much advantage from early sown lines this year, but when the moisture is around, we’ve seen that they can get their roots down deeper and access moisture from further down in the profile, which is a real plus when there is a dry finish.”
Dr Hunt said the long season varieties were able to grow roots around 30cm longer than their shorter season counterparts.
Interestingly, this year, the long season varieties in the Riverina benefitted from a late rain that the May-sown crops did not.
“It would make sense that the later varieties hang on later, but because the early crops had tapped into moisture deep down they were still going when the November rain fell, whereas the other ones were already finishing off,” he said.
Dr Hunt said the restriction on planting long-season varieties was getting the initial moisture.
“You obviously need to get a good 25mm rain event in April to make sure the crop will come up.
“There are years the break isn’t early enough, and if they don’t come up early, being long season lines, they will run the risk of heat shock in the flowering period.”
Dr Hunt said the advice for Bolac was for an optimum sowing date of April 25.
However, he said many farmers still used this as a starting point.
“Ideally, April 25 would be in the middle of the plant, with some going in earlier and some later.”
He said he believed many farmers were still too worried about possible frost risk at flowering to go in too early.
“Frost is incredibly devastating, but our trials found that in the high yielding lines, there was some frost damage, however when the yields are 8t/ha as at Westmere in Victoria, it is clear there are big advantages of getting the crop in on-time," he said.
“We’ve seen 13-47pc yield advantage with these lines in the trials in medium and high rainfall zones.”
Dr Hunt said another management advantage was that farmers were better able to manage the sowing period.
“By spreading out the sowing window, there’s less pressure to get everything in at the same time.”
On the downside, Dr Hunt said there was a risk of producing too much biomass, especially in the medium rainfall zones, where tight springs can occur, meaning a plant has too much biomass to fill grain in the head properly.
However, he said farmers could manage this with lower sowing rates, or in-crop nitrogen applications rather than up-front pre-drilling urea.
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