The 2014 cropping season in southern New South Wales has provided researchers investigating the benefits of early sown wheats with new insights and learnings.
Growers in southern NSW are used to dealing with frost at flowering in spring, and switching to slow maturing cultivars when sowing early is essential to avoid flowering frost damage.
However, 2014 was a bit different in that southern NSW was one of the regions hardest hit by stem frost during last year’s winter. Combined with heavy infestations of aphids, which transmitted barley yellow dwarf virus (BYDV), due to the above average temperatures in May, the detrimental impact on crops was significant.
And although Grains Research and Development Corporation-funded early sowing trial sites were affected, researchers say the impact was not as severe as expected.
“Early sowing was not the disaster many thought it would be,” said CSIRO researcher James Hunt.
“As a general rule, yield of early sown crops tended to be the same or slightly less than main season crops.
“To put 2014 into perspective, early sowing of slow maturing cultivars in southern NSW did not work as well as it has in previous years, but it wasn’t terrible and this was the first year for a very long time where sowing early wasn’t by far the most profitable thing to do,” Dr Hunt said.
Speaking at recent GRDC grains research Updates in the southern region, Dr Hunt said results from trials at Junee and Rankins Springs, as well as general grower experience, highlighted some lessons for managing early sown crops into the future.
“While the stem frost of 2014 was unprecedented in extent and severity, we can’t ignore the potential for it to happen again.
“There are convincing links between the increasing occurrence and severity of frost events in south eastern NSW and anthropogenic climate change.
“Periods of above-average temperatures during autumn are also likely to increase in frequency as the earth warms, which have the potential to accelerate the development of crops and make them more vulnerable to frost. It will also change the behaviour of insect vectors of viruses such as BYDV.
“We therefore have to learn what we can from 2014 in order to manage these risks into the future.”
Dr Hunt said major lessons from trials and grower experience in southern NSW in 2014 were:
- If planting before April 20, winter wheats are at lower risk of stem frost damage than slow maturing spring wheats. This is because winter wheats are slower to move from the vegetative to reproductive stage than slow maturing spring wheats. Winter wheats also have greater frost tolerance than spring wheats when both are in the vegetative stage. Provided they flower at the same time, yields of the best winter wheats are equivalent to yields of the best slow maturing spring wheats;
- Keep spring wheats within 5-7 days of their optimal sowing date. A lot of the crops that were badly affected by stem frost were sown much earlier than their optimal sowing date. Unless it is a very dry year, there is no real upside to sowing much earlier than a cultivar’s optimal date;
- In early-sown crops, be prepared to back-up imidacloprid treated seed with foliar insecticides if aphids are persisting later into autumn. Common wisdom in New Zealand is that imidacloprid activity ceases at the start of tillering.
Dr Hunt has been overseeing GRDC-funded early sowing trials throughout the south.
“Last year we had a range of trials running across the southern region in central and southern NSW, Victoria and South Australia and in each environment we investigated how to get the best out of early sown wheat crops. The rules generally held up that slow maturing cultivars that are well-adjusted to a region yielded more than the fast varieties did.
“The general theory of early sowing is that slow maturing cultivars sown early yield more than fast maturing cultivars sown later. These varieties use more water because their roots grow deeper, and they lose less water to evaporation as they cover the ground faster. Additionally, they grow at a time of year when water is converted to dry matter more efficiently,” Dr Hunt said.
“The trials were positive overall and provide some clear recommendations for growers and agronomists to consider in their local region. There are new winter cultivars currently in the pipeline and these will have significant yield advantages over what is presently available,” said Dr Hunt.
“We saw some really positive signs with early sown winter wheat varieties. For example, at Rankins Springs the highest yields we saw were from winter wheat cultivars sown in mid-April. They actually out-yielded the best spring cultivars sown in mid-May by 0.8 t/ha despite being more than three decades old in some cases,” said Dr Hunt.
“What growers can take away from this is that the benefits of using slow maturing varieties with early sowing are in some part due to better use of stored soil moisture such as from long fallows in certain regions.”
To view an interview with James Hunt at the 2015 GRDC grains research Update at Wagga Wagga please visit: http://youtu.be/mI0uTQp9Dj4.
James Hunt, CSIRO
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Caption: CSIRO’s James Hunt, speaking at a GRDC grains research Update, says as a general rule, yield of early sown crops tended to be the same or slightly less than main season crops, despite the impact of frost and disease in NSW in 2014.
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