Winter-spring cross opening new canola chapter
GroundCover™ Issue: 137 November - December 2018 | Author: Jo Fulwood
Biophysical-economic modelling by Agriculture Victoria in a GRDC-invested project has shown the yield upside of a winter-spring canola cross when planted in the higher-rainfall zones
Australia’s focus on spring canola varieties could be costing canola growers in the high-rainfall zones millions of dollars in lost yield potential, trials suggest.
GRDC-invested field trials combined with biophysical-economic modelling are demonstrating many high-rainfall areas across southern Australia could see yield benefits of between 0.5 and 1 tonne per hectare if canola varieties with increased vernalisation requirements (the need for some cold temperatures before flowering) were made available.
While winter canola varieties have limited appeal in the Australian environment, winter-spring crosses, which would introduce a small level of vernalisation, could be the answer for these higher-rainfall zones.
Field trials of two winter-spring canola crosses, which are not yet commercially available, have been run throughout southern Australia, ground-truthing the biophysical-economic modelling that is showing the yield potential of these varietal crosses.
The trials compared two winter-spring cross cultivars with a spring variety and a winter variety.
Trials were run across the southern cropping region at Kojonup and Merredin in Western Australia; Bool Lagoon in South Australia; Hamilton, Westmere and Inverleigh in Victoria; and at Cressy in Tasmania.
The trials found both the winter variety and the winter-spring cross varieties would have a yield improvement over spring varieties in 64 per cent of the study area.
Agriculture Victoria’s senior research scientist Brendan Christy has used the Catchment Analysis Tool (CAT) biophysical modelling framework developed by Agriculture Victoria to determine expected canola yields of the tested spring, winter and winter-spring cross cultivars over 50 growing seasons (1968–2017) (Figure 1) to produce a series of maps showing the areas that could benefit from access to a winter-spring canola cross.
Mr Christy says the data is demonstrating that more breeding is needed to produce canola cultivars better suited to Australia’s high-rainfall zones.
Spring canola types, or short-season varieties, with almost no vernalisation requirements have been generally bred to suit Australia’s medium and low-rainfall zones in an attempt to avoid the terminal drought conditions often experienced by crops in large areas of Australia’s grain-growing regions.
Vernalisation is the dependence on a period of cold temperatures to trigger flowering in a plant. A winter variety has a long vernalisation period, as compared with a spring variety that has almost no vernalisation requirement.
Spring varieties are particularly suited to areas that often experience dry conditions in spring, where flowering and seed-set must begin in July.
Trial data included as part of Mr Christy’s research showed the benefit of this short-season spring type in Merredin, in WA’s eastern wheatbelt.
However, the research also demonstrated the potential value of a winter-spring cross for high-rainfall areas.
Mr Christy says seven out of the eight field locations achieved superior 50-year average yield responses for these winter-spring crosses when sown on an autumn break, with the sole exception being the Merredin trial site.
“One of the benefits of introducing a vernalisation period into a canola variety is the earlier sowing opportunity and the greater control over the time of flowering – which allows a higher level of confidence in regions particularly susceptible to waterlogging and very cold temperatures,” Mr Christy says.
“In these higher-rainfall zones, where winters can be very long and very cold, forced flowering in July, which is what occurs in the spring varieties, could be reducing yield opportunities.”
According to the research, if growers in these higher-rainfall zones had access to a winter-spring cross, yields across the region could increase by more than 350,000 tonnes, (based on the area sown to canola in 2015 data from ABARES) adding $185 million to growers’ pockets.
Mr Christy says breeding efforts have traditionally been focused on producing blackleg resistance and reducing photoperiod requirements for flowering, thus allowing for canola to be pushed out into the lower-rainfall zones.
CSIRO Agriculture and Food conducted two years of field experiments to evaluate the performance of these winter-spring crosses at Kojonup in the high-rainfall area of WA in 2016 and 2017.
The trial results showed these winter-spring crosses produced 8 to 16 per cent more yield than the current spring type, representing an additional 250 to 400 kilograms per hectare of yield over spring canola.
CSIRO principal research scientist Dr Heping Zhang says the growing season requirement of the winter canola was too long for WA’s high-rainfall zones and produced a lower yield than spring canola simply because it ran out of water and time to fill the pods.
“However, the winter-spring canola cross produces canola with the flowering time that fills the gap between the current spring canola and winter canola and provides opportunities for growers to sow in late March and early April without running into frost damage problem at pod development stage,” Dr Zhang says.
This wide-ranging GRDC-invested project involves a multidisciplinary team with research scientists working closely with growers through field days, field walks and grower discussion groups investigating the value of the different canola types.
Researchers have also relied on input from the seed companies and breeders, who provided the project with genetic material and ongoing support for the work.
While spring canola varieties have dominated the Australian cropping landscape, winter varieties do have a fit in some very high-rainfall zones and can be found in mixed-farming operations particularly in Victoria and Tasmania.
In WA, winter canola has struggled to garner much interest because of the long vernalisation requirement of these varieties, coupled with the need for enough summer rainfall to ensure crop growth over summer if grazing is to be an option.
However, a handful of WA growers have trialled small areas of the winter crop, with surprising results.
Rob Egerton-Warburton – Kojonup, WA
Kojonup grower Rob Egerton-Warburton planted 60ha of winter canola in spring 2016, harvesting it in late 2017.
Despite a very dry summer and a long dry autumn period, plus intensive grazing during the autumn feed gap, the crop went on to yield 1.8t/ha after being in the ground for 14 months.
Rob farms in a high-rainfall zone in WA’s Great Southern region and says, in comparison, his hybrid short-season spring canola would yield, on average, about 2.4t/ha.
“So, we took a yield hit, but there were a range of other benefits with this crop that might end up outweighing that reduced yield,” he says.
One of Rob’s biggest cropping challenges is waterlogging, and the benefits of such a long-season crop have come to the fore in this season, where waterlogging on that paddock has not been a problem, despite the very wet conditions.
He says during August, he could not get on his other paddocks to spray simply because it was too wet.
“Having a crop in the ground for 14 months really dried out the soil profile, and in this wet year our wheat on that paddock is not suffering from the same effects of waterlogging that some of our other crops are faced with,” Rob says.
Another major bonus for his mixed-farming enterprise is the nutrient-rich feed source for his sheep flock during the autumn gap – which has direct economic ramifications.
“The crop was a fantastic source of green feed when feed was so tight in that dry start to 2017. We had millet and sorghum planted as well and they were also really valuable,” Rob says.
“All we had to do is run the weaners through it for one week once a month and they got all the nutrition they needed.”
Rob is quick to point out there were challenges with a crop that stayed in the ground for such a long period, particularly in relation to weed control.
Despite that, he is interested in the possibility of new opportunities with a winter-spring cross canola – particularly one that does not need to be in the ground as long as a winter variety.
“There is definite potential for a winter-spring cross variety in this area, where the vernalisation period is longer than a spring variety but not quite so long as the winter canola we used in 2016-17, but we would probably want it to be Roundup Ready® so we had some flexibility with weed control,” Rob says.
“When you have a crop growing for that long, the regermination of weeds is a big issue, and we need different technology to kill these weeds.”
He says the sheep did help to manage the weeds in that 60ha simply because they ate canola as a last resort.
“Sheep will graze everything else before the canola, particularly when the plant is water stressed,” he says.
John Wallace – Esperance, WA
Esperance grower John Wallace could see the potential of a long-season winter canola in his mixed-farming business, and as a result planted a Clearfield® variety in September 2017.
His twofold objective was to plant a cash crop that could also be grazed in the autumn-early winter feed gap, but also to hit a paddock full of doublegee weeds.
John admits it is a risky move and has heard of other growers trialling the canola with limited success.
“We are just giving it a go to see if it might be a profitable decision for the business, particularly since I needed an option in regard to attacking these weeds,” John says.
Since the variety is a Clearfield® hybrid, John has been able to use a Group B imidazolinone herbicide on the 60ha paddock.
So far John is hopeful the crop will prove to be worth the risk, particularly after surviving one of the driest summers the region has seen for many years followed by a tough grazing in autumn.
“We grazed it twice at a really high stocking rate of 700DSE (dry sheep equivalent) for two weeks in February and then two weeks in March, plus we have had cows on the crop since the start of the year,” he says.
John says the plant biomass was an excellent feed source for his sheep and cows.
“When we put the pregnant ewes that were scanned with twins into that paddock, their fat score improved from 3 to 4 after grazing on the canola plants.”
John says a winter-spring cross canola option would take some of the risk away from a longer-season canola in his region and would allow for a more robust plant before the season became too wet.
“It would allow us to take advantage of the full length of the season in this part of the world,” John says.
Todd Venning – Hamilton, Victoria
Hamilton grower Todd Venning only plants winter canola now, after giving on up spring varieties in his high-rainfall region years ago.
Todd’s growing-season long-term rainfall average is about 500mm and waterlogging and cold winter temperatures are some of his major hurdles when it comes to the cropping portion of his business.
The Vennings have a soil type of clay loam, or heavy loams with a clay base, meaning they only have limited plant-available water at any time of the season.
Todd says an early sown canola that has larger biomass early in the season becomes too heavy during the long cold and wet winter period and can perish or rot before spring arrives.
“Spring varieties flower too early in our country. We can’t match their stem elongation with enough soil mineralisation and the required nutrients,” Todd says.
“The cold soil temperatures and the waterlogging we usually experience in August mean the plant lodges with the large amount of biomass and it ends up crashing in that winter period.”
Unlike his WA counterparts, Todd does not plant the crop as a grazing option, although he says he may revisit this option in the next few years.
In recent years, he has planted his winter canola in May and harvested it in December-January, with exceptional results.
In 2016, he averaged 5.3t/ha, and in some parts of the paddock he was yielding up to 8t/ha.
That crop was planted in the last week of May: “We don’t necessarily need it to be in the ground for that long to yield well, we just need to time it right, so everything lines up,” he says.
“I can see the real long-term potential of these winter canola varieties as long as we can manage the plant development according to our season.”
Brendan Christy, Agriculture Victoria
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