Weed seed destroyer crosses the Nullarbor

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The Harrington Seed Destructor prototype’s performance in collecting and destroying weed seeds during the grain harvest was demonstrated for the first time to eastern states growers this harvest

- By Nicole Baxter

Grain grower and agronomist Kent Stone of Quairading, WA, joined Associate Professor Michael Walsh and University of Melbourne researcher Charlotte Aves on a 16-day road trip to test the Harrington Seed Destructor (HSD) prototype's performance across south-eastern Australia. Photo: Nicole Baxter

The latest weapon in the war against weeds is being put to the test in south-east Australia this year to demonstrate its value as a tactic to drive down the weed seedbank and fine-tune its development.

Associate Professor Michael Walsh, from the University of Western Australia, went on the road late last year with Quairading, WA, grain grower and agronomist Kent Stone and University of Melbourne researcher Charlotte Aves as part of a 16-day journey to test the Harrington Seed Destructor (HSD) prototype at 14 trial sites.

The sites, set up to compare the HSD prototype with other management tactics such as narrow windrow burning and seed collection with chaff carts, were spread across South Australia, Victoria and New South Wales.

It was the first time the GRDC-supported HSD prototype had been tested outside WA, giving eastern Australian growers their first glimpse of the machine at work. The HSD prototype works by being coupled to the rear of a header where it collects and mills weed-seed bearing chaff.

Despite hydraulic motor problems, which slowed harvesting, the tests allowed more than 400 growers to witness the HSD prototype in action and ask questions about its performance and reliability.

At each trial site Associate Professor Walsh explained how the HSD prototype works, highlighting the central role of the counter rotating cage mill.

He said the mill, originally designed for the mining industry, operating at 1400 revolutions per minute is more than capable of processing the chaff produced by a John Deere 9650 header operating at its capacity of 25 tonnes of wheat per hour.

“Tests have shown that the faster the mill goes, the better the seed kill,” he said. “At 1300 rpm we know that we are getting a 98 per cent kill of annual ryegrass seed.”

A pneumatic chaff transfer system, similar to those on chaff carts, moves the weed-seed bearing chaff to the mill. Upon exiting the mill, the processed material is blown into straw choppers at the back of the HSD prototype and then spread with the straw across the header swath.

Previous trials in a 3t/ha crop at Wongan Hills, WA, showed that the HSD prototype can kill 98 to 99 per cent of ryegrass, 98 per cent of wild oats, 95 per cent of wild radish and 96 per cent of brome grass introduced to the front of the machine.

Associate Professor Walsh said high weed-kill results depend on capturing a high number of weed seeds with the harvester. “If you don’t get into the crop early enough some weed seed may shed and the weed kill using the HSD prototype could be as low as 50 per cent.”

Tests in WA during 2010 showed no difference between the HSD prototype, narrow windrowing and chaff carts in reducing ryegrass emergence.

For the 2011 trials across south-east Australia – supported by the Rural Industries Research and Development Corporation – ryegrass counts will be conducted following autumn rainfall.

Associate Professor Walsh said the ryegrass densities at the trial sites before harvest were one to five plants per square metre; enough to produce 1000 to 5000 seeds per square metre.

At the Old Junee, NSW, trial site (being run in collaboration with FarmLink Research) seed producer Robert Hart said Treflan® and Avadex® BW had been applied, but weed control was marginal due to a lack of rain.

Mr Hart and his family have a seeding bar set on 335-millimetre row spacings with press wheels and about 25mm of rain after sowing is needed to achieve satisfactory early season weed control.

The Harts, who continually crop their farm, were keen to test the HSD prototype as they want a mechanical tactic to lower weed seed carryover into subsequent crops; that will also allow them to stop burning.

“We retain our stubbles for moisture conservation and like to keep as much organic matter as possible,” Mr Hart said. “Burning leaves the paddocks too bare.”

Associate Professor Walsh said plans were on track to make the HSD available to farmers in time for harvest 2012. 

A numbers game

Effective harvest weed management is a numbers game that aims to prevent the maximum numbers of weed seeds from returning to the seedbank.

Late last year, the Harrington Seed Destructor (HSD) prototype was demonstrated in SA, Victoria and NSW with some interesting numbers to note.

14  trials were established to test the HSD prototype against narrow windrow burning.
7  sites included a chaff cart treatment.
6  sites were in SA: two at Minnipa and one at Cummins, Bute, Athurton and Pinaroo.
3  sites were in Victoria: Underbool, Dimboola and Dookie.
5  sites were in NSW: Rand, Old Junee, Harden, Peak Hill and Coonamble.
4000  kilometres were travelled to test the HSD prototype at trial sites from Minnipa on SA’s Eyre Peninsula to Coonamble in northern NSW.
3  litres/ha of fuel is used to drive the HSD prototype.
7  t/ha of wheat was the highest yielding crop put through the HSD prototype during the trials – it was found at Andrew Davey’s property at Athurton on SA’s Yorke Peninsula.
16 days were needed to establish the 14  trial sites.

IMAGE CAPTION: Grain grower and agronomist Kent Stone of Quairading, WA, joined Associate Professor Michael Walsh and University of Melbourne researcher Charlotte Aves on a 16-day road trip to test the Harrington Seed Destructor (HSD) prototype's performance across south-eastern Australia. Photo: Nicole Baxter

GRDC Research Code UWA00124

More information:
Michael Walsh, 08 6488 7872, michael.walsh@uwa.edu.au;

GRDC Project Code UWA00124

Region National