INVESTIGATIONS into chemical residue by CBH Group has revealed poor firebreak application can lead to chemical residues in grain.
To help maintain market access and the reputation of the grains industry, CBH undertakes rigorous chemical residue screenings of grain delivered into the network every year.
The information gathered in those screenings helps to export grain in line with its customers and destination requirements.
Firebreaks are often created by applying a non-selective herbicide to a two to three metre strip around the edge of a paddock.
CBH senior specialist and agronomist Steven Tilbrook said when done correctly this could be extremely effective, but there could be a risk of creating chemical residues in grain in neighbouring crops.
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"Small amounts of spray which drifts onto a crop or late application to a crop area have the potential to cause chemical residues in grain," Mr Tilbrook said.
"Firebreaks can be a small part of a growers' program and as such cropping tasks can be prioritised, delaying application.
"Many of the techniques used to achieve a functional firebreak and minimise the risk of herbicide resistance developing will also aid in reducing the risk of chemical residues in grain."
Consider application timing
Applying herbicides earlier rather than later means targeting younger, smaller weeds which are easier to control.
Applying herbicides no later than booting for cereals or first flower for canola or legumes also reduces the risk of chemical residues in grain.
Once crop plants are more advanced, a small dose of herbicide is more likely to cause a residue in the grain.
Residual herbicides
Mr Tilbrook said not only do residual herbicides reduce the resistance selection pressure placed on knockdown herbicides, but it also means firebreaks will not need frequent application of herbicides.
"These treatments can also be applied in the weeks before the breaking rains providing flexibility for growers and removing the risk of chemical residues in grain," he said.
"Take care when applying residual herbicides near native vegetation and trees and consult your agronomist for the appropriate option for each situation."
Drift reduction
To reduce spray drift, growers should use a purpose-built firebreak sprayer with a shroud around all sides.
A shroud can be effective when made with rubber, plastic, metal or brushes and can be constructed to fit around the boom to further reduce drift.
Selecting low drift nozzles that are capable of a very coarse spray quality as a minimum will reduce spray drift onto crop areas.
Mechanical fire breaks
"If it is late in the season consider a mechanical means such as ploughing, grading or even incorporating cutting a lap for hay," Mr Tilbrook said.
"All of these non-herbicidal controls can provide a functional firebreak and an alternative means of controlling weeds to avoid herbicide resistance."
Set crop boundaries away from fire breaks
Avoid overlap of firebreaks and cropping areas.
Create the boundaries two to three metres away from a fence where a firebreak is required.
