More water may lift herbicide hit

Photo of woman in a paddock

MacKillop Farm Management Group research and operations officer Felicity Turner says preliminary research suggests using higher water rates can improve pre-emergent herbicide efficacy.


Preliminary results from a trial in the south-east region of South Australia suggests higher water rates (of up to 100 litres per hectare in a trifluralin/Avadex® Xtra mix or 150L/ha for other products) can improve the efficacy of pre-emergent herbicides in stubble-retained systems.

The project by the MacKillop Farm Management Group (MFMG) is part of the GRDC’s Maintaining Profitable Farming Systems with Retained Stubble Initiative.

One of the issues identified by MFMG members in retained-stubble systems is achieving good control from pre-emergent herbicides prior to sowing cereals. This trial is trying to address some of these issues by investigating ways to maximise the benefit of newer pre-emergent chemistries such as Sakura® and Boxer Gold®, and existing chemistries in trifluralin and Avadex® Xtra, to manage seedbank numbers.

The trial is taking place at MFMG’s Sherwood site, east of Keith in SA. Water rates being trialled are 50L/ha, 75L/ha, 100L/ha and 150L/ha sprayed into four tonnes/ha of stubble in a wheat/wheat rotation.

MFMG research and operations officer Felicity Turner says the reason behind the research was anecdotal evidence filtering through from other regions that Sakura® was working more effectively at higher water rates.

“The aim was to make sure we can get maximum benefit out of these newer chemistries to avoid resistance problems early,” she says.

Early results from the project suggest higher water rates do improve the efficacy of ryegrass control, particularly with Sakura®.

“We half-expected that this would be the case, but wanted to validate it in a south-east SA system,” Mrs Turner says.

Best results came from a water rate of 150L/ha, while good control was still evident at 100L/ha. However, at 50L/ha, Mrs Turner says weed numbers were double what they were at 150L/ha.

“There was still a good level of control at 50L/ha, but not as good as 150L/ha,” she says.

The project follows on from work completed in 2013 by MFMG on different stubble-management practices and the effect of herbicide efficacy in those systems. Those treatments included burnt stubble, stubble harvested high, stubble harvested low with trash retained on surface and a disc-treated plot.

Mrs Turner says she hopes to replicate the herbicide trial again this year (2015) to evaluate the environmental effects of the 2014 trial.

“The 2014 trial was sown in a really wet month but we’ve had next to no rain on it since,” she says. “We want to look at the differences between herbicide mixes, so we are hoping to conduct the trial again this year as there may have been environmental effects on herbicide efficacy. This trial is being mirrored by the Lower Eyre Agricultural Development Association on the Lower Eyre Peninsula under different environmental conditions, so it will be interesting to compare the results.”

By the end of 2015, the MFMG will have developed a management guideline specific to the south-east region that will enable growers to better manage herbicide efficacy in retained-stubble systems.

More information:

Felicity Turner, MFMG,
0400 299 087,


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GRDC Project Code MFM00006

Region South