Keeping weeds down in crops is a high priority on most farms, yet herbicide resistance can quietly increase along fencelines.
Having a ‘set and forget weed control option for these areas could save money and arrest the evolution of herbicide resistance in weeds.
In vineyards the under-vine area is often kept bare using a limited number of suitable herbicides, opening the door to herbicide resistance.
Populations of glyphosate-resistant annual ryegrass and fleabane have been confirmed in Australian vineyards and along fencelines and roadways.
Having worked previously in broadacre cropping, and more recently in the wine industry, research agronomist Chris Penfold, University of Adelaide is interested in identifying alternative ways to manage under-vine and mid-row areas in vineyards, which also has implications for fencelines on grain and mixed farming properties.
“In many cases it might be better to replace weeds on the fencelines with a competitive but palatable option,” he says.
“In vineyards, the continual use of herbicides and cultivation for weed control under the vines has a long-term detrimental effect on soil health and grape quality.
“Consequently, our research aimed to identify cover crop species that would build soil health and conserve soil moisture for the vines.
“Since this is not a priority on grain farms, a range of other options might be chosen but the principle can remain – establish permanent cover and stop fenceline spraying,” says Chris.
“By not applying herbicide to fencelines growers will save money, which can be partly re-directed to the establishment of effective living mulches to provide a long-term management solution to stop fencelines being a source of herbicide resistant weeds.”
Another option Chris has investigated is in-crop grazing with sheep. With living mulches growing around the borders, sheep can be allowed to graze in established crops at light stocking density.
“The sheep will preferentially graze the in-crop weeds and may also assist with weed control along controlled traffic wheeltracks, especially if weed seed is directed onto the wheeltracks using a chaff-deck for harvest weed seed control.
“Sheep are selective grazers and lambs are more selective than older sheep,” says Chris.
Where pastures are part of the crop rotation it can be as simple as establishing the pasture species along the fencelines and leaving them in place when the paddock rotates into the cropping phase.
Similarly, the crop can be sown right up to the fenceline and either mown or baled for hay prior to harvest.
This article was first published in The Fence magazine.