Taking the guess work out of herbicide residues

At BCG’s Trials Review Day, on Friday 19 February, growers will learn the key tools and strategies that can be used to assess their herbicide residue prior to sowing.

Dr Mick Rose from News South Wales DPI and BCG’s Kelly Angel will share results from the recently concluded Grains Research and Development Corporation project that found between 5-15 percent of surveyed paddocks contained levels of sulfonylureas or trifluralin that could reduce seedling vigour of some crops. Damage was avoided in most cases by growing tolerant crops.

“Growers also identified imidazolinone (group B) and clopyralid (group I) residues as potentially damaging to crops or constraining rotation options. However, the exact loss of productivity due to herbicide residues as a soil constraint in the past has not been accurately determined due to the lack of tools to measure herbicide residues and quantify herbicide damage,” Dr Rose said.

“There are questions about whether herbicide residues will cause issues beyond the ‘label’ plant-back period under certain conditions, because the persistence and behaviour of these residues depends on numerous site-specific factors including soil chemistry, organic matter, microbial activity and climatic conditions.”

Dr Rose and Mrs Angel will discuss recent trial work funded through the Co-operative Research Centre for High Performance Soils.  “The project aims to give growers and consultants more confidence in knowing when herbicide residues may be an issue and how to avoid these risks,” Dr Rose finished.

The discussion will include how site-specific factors such as environment and soil type can be used to determine how long is ‘long enough’ (after the label plant back period ends) before planting a susceptible crop.

“This will be an invaluable session for growers to attend as they continue to plan their 2021 growing program,” Mrs Angel said. “If growers can accurately calculate a paddock’s herbicide residue risk, this allows them to then choose the best crop type and variety for yield, weed and disease management for their cropping program. It really is a discussion not to be missed.”

BCG’s Trials Review Day, to be held at the Birchip Leisure Centre, is a members’ only event. Attendees are encouraged to register online at

https://www.bcg.org.au/events/. The event will be adapted to suit a socially distanced and digital audience.

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