We can’t afford to lose older chemistries
The Linklater family – Ian and his three sons, Daniel, James and Michael – of Trentham Farms, near Gol Gol, NSW, crop 9800 ha of sandy loam country and appreciate the value of older and cheaper herbicides that are still effective options against their major weeds.
With a focus on maximising yield by cropping as often as possible, Daniel says it is necessary to take a medium to long-term view when making decisions rather than focusing on the lowest-cost options in a single season.
“In 1981, Dad bought Trentham Cliffs Station and started clearing the mallee to establish a simple rotation of wheat on long fallow,” says Daniel. “In 2000, he bought a Concord seeder with knifepoints and a Goldacres spray cart and began zero-til farming. Wheat varieties were alternated to reduce disease risk, and we made it through the Millennium drought.”
Things turned in the wrong direction in 2010 when a large infestation of brome grass was evident on the farm. There was good rainfall over the 2010-11 summer, but their 2011 wheat crop couldn’t compete with the weeds.
“While neighbours were harvesting 2 t/ha wheat crops, we were harvesting only 0.6 to 0.8 t/ha due to the weeds – it was clear the system had to change,” he says. “In 2012, we planted half the farm to canola for the first time and the other half to Clearfield wheat, and entered a new era of in-crop spraying for brome grass.”
Having used ‘imi’ herbicides heavily for a few years to drive down the brome grass seed bank, the Linklaters have reduced their use of this mode of action to preserve its efficacy.
In 2013 the Linklaters saw the benefits of legumes in rotation in a Mallee Sustainable Farming trial and subsequently introduced chickpeas to their rotation in 2014 and then lentils in 2017. Daniel says the benefits for their farming system were evident in 2016 when barley on chickpea stubble went 4 t/ha compared to barley on barley stubble yielding just 2 t/ha. In addition, they also harvested 2 t/ha from the chickpea crop.
In 2019, the Linklater’s crop rotation and weed management program rewarded them with a 2 t/ha wheat crop grown on just 100 mm of pre-sowing rain and 75 mm of growing season rain.
“The value of the break crop pays for the additional chemical treatments and has improved the overall profitability of our farming system,” says Daniel. “We now avoid consecutive cereals and have lengthened the break between legume crops to avoid disease outbreaks. Going forward we plan to increase the use of lentils and canola in the crop rotation.”
Daniel says adding Round-up Ready canola to their program will enable them to use propyzamide to reduce pressure on Group 1 [A] herbicides. Although propyzamide is a more expensive pre-emergence herbicide, the high-value canola crop counters the extra cost.
“In the Mallee, we can’t afford to miss a planting opportunity and keeping weed numbers low is key to storing soil moisture,” says Daniel. “We have been using the double-knock to good effect pre-sowing in most years since 2011 to take pressure off the Group 1 herbicides in our break crops particularly. In 2021 we successfully tackled a spiny emex problem with a Kelly chain operation followed by a chemical double knock before planting wheat.”
The Linklaters have been proactive in applying the WeedSmart Big 6 program and have proven the benefits of crop rotation and adopting new technology such as herbicide tolerant varieties and optical spot sprayers to protect older and cheaper chemical options into the future.
The WeedSmart Big 6 is an integrated weed management program that growers can apply across all cropping systems. A diverse approach that includes several chemical and non-chemical tactics places downward pressure on the weed seed bank and reduces herbicide resistance risk.
