A long-awaited trial was harvested at Tarlee in December, one that was possible because of the recent lifting of a moratorium on genetically-modified crops on mainland SA.
The Mid North High Rainfall Zone Group site was home to a 0.2-hectare trial that examined the weed control management strategies growers could adopt in a GM crop, namely the new Roundup Ready and TruFlex canola varieties, compared with a conventional system.
Tarlee GM site manager Tim Murphy from Bayer - the company that provides the RR and TruFlex technologies to seed companies - said the trials gave an insight into what flexibility a farmer had to apply different herbicides on their weeds in-crop.
It is one of seven GM trials across SA managed by farmer and agronomy groups.
"These trials have already been conducted in other states, but farmers always want local results," he said.
Collaborating with the MNHRZ Group, Bayer had 18 different treatments replicated in the trial.
Some plots examined using pre-emergents, their impacts on the timing of applying RR herbicide, and whether it eliminated all weed pressure, while others looked at what happens if a grower missed a treatment, weeds built up, and only the RR herbicide treatment was used.
"We looked at whether full control could still be achieved, or whether there was a yield penalty because of weed pressure," Mr Murphy said.
Other herbicides were also included to help in the fight against glyphosate resistance.
Mr Murphy said the late, dry start to the season resulted in a staggered germination and allowed weeds to thrive more than normal.
"This was fine for the timing of some of the plots, particularly where TruFlex technology was used, as we were able to apply herbicides a bit later and got really good control," he said.
"But where we were using the RR canola technology, which can only be sprayed up to the six-leaf stage, a lot of the weeds germinated after that stage and we couldn't come back in with a control then.
"This highlighted the big difference in the two traits.
"In TruFlex crops, we can spray right up to the first flower, while with the RR canola varieties, you can't spray after the six-leaf stage - it really shortens the spraying window, so you really had to be on the ball with it last season."
(The GM canola trial) highlighted that growers need to have a full program of weed control management, using both pre-emergent herbicides and in-crop sprays.- TIM MURPHY
Mr Murphy said the best performance came from plots that used a combination of a pre-emergent herbicide and in-crop spray, where weeds were controlled when they were young.
"So whether it was Overwatch or propyzamide, we got longer term control and those plots started cleaner," he said.
"It highlighted that growers need to have a full program of weed control management, using both pre-emergent herbicides and in-crop sprays.
"Where a full integrated weed management program was used, which included a pre-emergent, followed by something like a clethodim in that first spray with the RR herbicide, that was able to give us really good control, we were able to use different modes of action, which helps to avoid glyphosate resistance and there was no issue getting those extra herbicides in."
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Harvest was conducted in mid-December, with yields in the untreated plots reaching 1.8t/ha, while the full spray program plots yielded up to 2.8t/ha.
Mr Murphy wasn't surprised the new GM varieties yielded well - "because they have improved genetics".
"The open pollinated varieties yielded quite a bit lower in comparison, purely on vigour and because of poorer weed control throughout the season," he said.
"That's the benefit of GM - being able to use herbicides at the most strategic time, when you can get the biggest bang for your buck."
Mr Murphy said the trial would be replicated at Tarlee next year.
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