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Success in tackling weeds

With the harvester back in the shed and seeding around the corner, it’s the time of year when summer spray regimes are front of mind.

Rising chemical costs, greater summer rainfall and the increasing incidence of herbicide resistance mean summer spraying is serious business.

Gnowangerup farmer Knud Nymann is using every trick in the book to attack weeds, and a combined control approach is helping him reduce his summer weed burden.

Maintaining livestock in his operation as well as the recent incorporation of chaff carts and light cultivation methods play an important role in weed control on his 12,000 hectare property which spans the Great Southern region from Gnowangerup to Wellstead.

But for Knud, it was a targeted approach to spray application that not only led to considerable cost savings and reduced environmental impact, but has proven to be the most effective method for successful weed knockdown.

Since introducing Weedit spray technology three years ago, Knud said he had saved up to 90 per cent in herbicide costs.

The technology actively detects live plant matter, only applying chemical when a target plant is detected rather than the blanket fence-to-fence application method used in conventional systems.

Knud started with a 24-metre, hired Weedit unit in 2011, and today uses a 36m unit which is a key tool in his summer spraying toolbox.

“The cost savings are pretty straight forward because if you spray 1000ha and you use a brew that cost $20-$25 and you only spray 10pc – say 100ha out of the 1000ha – then you saved yourself a fair bit of money because it only cost you $2500 in chemicals when it would have cost you $25,000,” Knud said.

“The strike rate will vary from job to job and the year.

“At home this year the weed percentage was only 6pc, so if you work on 10pc chemical use you save 90pc.”

With a cropping program of 11,000ha, Knud said it was easier to justify the expenditure in a bigger operation because although the technology was expensive the potential savings were greater.

“The machine pays itself off relatively quickly but obviously the more weeds you have the slower it pays off,” he said.

Courtesy Farm Weekly

Courtesy Farm Weekly















Knud said he had noted herbicide resistance issues on-farm, particularly glyphosate resistance in Fleabane and Windmill Grass, and although the cost of older existing chemicals hadn’t increased greatly, he had found he needed to use more to achieve comparable results, which meant the cost per hectare of spraying had increased.



“We used to use 150ml of Select to kill ryegrass immediately and now we use half a litre instead,” he said.

“The good thing about the Weedit is you could start using newer, more expensive chemicals, because you are only using so little of them.”

In addition to cost savings, Knud said targeted chemical application had environmental advantages.

“With target application, the environment is obviously not exposed to all these chemicals that are sprayed out on the bare dirt for nothing,” he said.

“You are only striking when there is something to strike for.”

Although pleased with the system, Knud had a few words of caution for those looking to utilise detector spray systems.

“Don’t skip rates when using detector spraying systems, go hard,” he said.

“And conditions are still king, if we do go into warm conditions a spray oil for prep purposes is an absolute must.”

Knud said significant rain on his Wellstead property meant he could only spray a quarter of the program with the Weedit this summer because weed percentages were too high for the process to be viable.

“With strike rate success on Fleabane, depending on size and what brew you use, don’t expect to be getting two thirds or three quarters,” he said.

“Fleabane seems to be extremely hardy.

“We are actually going back to the old double knock in the summer weed context for Fleabane.

“If you have an 80pc strike rate, the last 20pc is still there and it’s a worry.

“We did some spraying with the Weedit, about 1100ha but some of the percentages were too high so we actually sprayed them fence-to-fence.

“We will see if the fence-to-fence was a lethal dose, because it gets pretty expensive with Fleabane.

“And then we’ll go back over it with the Weedit.”

Mr Nymann said he also dabbled in light cultivation, using discs as a way to vary the method of controlling the weed burden.

“You can’t do too much of the same thing,” Mr Nymann said.

“Cultivation is also incorporating the stubble into the dirt.

“It is a misconception that the stubble should stay up in the air – it should be down where all the microbes are.”

Mr Nymann said he had also invested in chaff carts as another tool in combating weed issues and they were largely used on the Wellstead property.

“A chaff cart is a fair bit of outlay so we decided to drop windrows this year just to see how that goes,” he said.

Mr Nymann said chaff carts worked in well with his livestock and weed control program.

“We generally run 350 black breeder cattle in Wellstead, and mate 2800 Dohne ewes,” he said.

“Even when you go in with a detector sprayer, having livestock in the mix is always beneficial.”

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