Killing weeds at harvest

Different approaches same goal for weed management

Wimmera farmer Alexander McRae, left and Ash Teasdale were among those at the recent Weed Smart Week event.

Wimmera farmer Alexander McRae, left and Ash Teasdale were among those at the recent Weed Smart Week event.


The market is awash with options for post harvest weed seed management, a group of farmers explained the pros and cons of different choices.


THE area of post-harvest weed seed management is increasing tricky for farmers to get a handle on.

There are so many options out there all with different pros and cons that need to be considered.

At this year's Weed Smart Week in Horsham, Victoria, last month a panel of farmers outlined what they were doing post-harvest to run their weed seed burden down and reduce the reliance on herbicides.

Seed Terminator

Victorian farmer and contract harvester Chris Bartlett, Pimpinio, has used a Seed Terminator unit on his header and gave glowing reports.

"We were initially sceptical about how the unit would go, but it just worked really well. We used it for around 100 rotor hours on a John Deere S770 header," Mr Bartlett said.

We were initially sceptical about how the unit would go, but it just worked really well. - Chris Bartlett, Wimmera farmer.

"It is important that you keep everything clean, you've got to have the pulleys clean because it gets hot, but if you do that it works really well."

Mr Bartlett said he felt the Seed Terminator, which has a reasonable horsepower requirement, would be better suited in lower yield regions than areas with big crops.

"It did struggle a bit with horsepower on the hills and the heavy crops down towards Skipton (in Victoria's Western District), but I think it would be a great fit in the Mallee, it certainly looks to do a fantastic job at capturing any ryegrass seed."

Chaff lining

Victorian Mallee farmer Mick McClelland, Sea Lake, uses chaff lining to keep problem weeds, in particular brome grass, under control.

He said chaff lining was slightly different to a dedicated harvest weed seed control unit in that it was more opportunistic in terms of effectiveness.

"In the dry years you can get 98-100 per cent control, but in a wetter year you can see the weed stems bend over under the front," Mr McClelland said.

He said with chaff lining, the most important thing was to get the weeds through the front.

"It is what you can get through the front that is the most important thing."

Mr McClelland said chaff lining was only a small part of his overall weed management strategy.

"Rotations and chemicals are 95pc of the weed management, the chaff lining is the icing on the top," he said.

"In really good circumstances you can consider it a weed break but in general its best to think of it as the last piece of the puzzle not the first."

However, he said it was cheap and little work, with no maintenance costs.

"It doesn't slow down harvest, it fits in well so I think I'll continue with it for a long time yet."

Lubeck farmer Ian Taylor uses narrow windrow burning and has been satisfied with how it has helped manage ryegrass.

"It is a great way of managing ryegrass, but getting your harvest height right is critical," Mr Taylor said.

He echoed Mr McClelland's thoughts that it was critical to get the weeds through the front.

Mr Taylor said in the past couple of years baling straw had also been an option, given the high price of straw, so the header was set up to take off straw for that option.

Harrington Seed Destructor

Craig Bignell, from Broomehill, in Western Australia's Great Southern region, has a vertical Harrington Seed Destructor (HSD) for use on his property in a 400mm annual rainfall zone.

The farm is set up for 70 per cent cropping and 30pc livestock.

Mr Bignell said he had made a gradual progression to the HSD.

"Chaff carts were the first step, we had good success grazing livestock on the chaff piles, they had good weight gains and we also worked at spray lining under windrows in both barley and canola."

From there he got a HSD.

Mr Bignell was involved with the team at McIntosh Engineering, who made the HSD, to set the machine up vertically rather than horizontally, which he said worked better and meant less crop losses.

Mr Bignell said he felt windrowing would be a big thing in managing weed seed set, especially with the threat of glyphosate being banned as a desiccant.

"We really aggressively swathed (windrowed) a while back and then stopped for a while, before starting due to lodged barley and we now realise its worth as a very important part of the overall plan."

Mr Bignell said he noticed in 2016 when windrowing due to lodged crops that ryegrass seeds in the windrows did not appear to be viable.

"It is a no-brainer to do it, it is a step in the right direction towards getting weed numbers down."

He said it required some adjustment when harvesting in terms of the reel set up and added it was important to get the windrower set up correctly so there were not losses, but said it was possible, even in lodged crops.

"Overall we don't seem to have issues picking the grain up."

However, a downside in the habitat the windrows provide for pests such as mice and damaging insects, such as slaters and earwigs.

Chaff cart

Gavin Hawkins farms in the Wimmera at both Minimay, in the far west of the region and at Lubeck, both in medium rainfall environments.

He has been using a chaff cart for some time after starting off doing narrow windrow burning.

"The windrow burns were alright, but they just didn't fit in with the sheep we have in our system, we couldn't graze the stubbles so we needed to look for something else to control the weeds."

With the chaff piles he said he waited until mid-autumn before burning them.

"We wait until April and we still get a good burn and we lower the risk of fire escapes."

He said the piles were reduced to ash and did not leave bare patches.

The chaff also provides valuable sheep feed.

"It has definitely got us further in terms of sheep feed over summer and early autumn than before."

"The grazing benefits are so big it keeps us in it."

Mr Hawkins said the piles could blow in the wind but generally it was not a big problem.

The cost of pile burns is calculated differently, some have it at around $2 a hectare, others at up around $5/ha.

Harvest weed seed management has been described as 'the holy grail' by the Australian Herbicide Resistance Initiative (AHRI), with the organisation saying it was a great start for farmers looking to run down their weed burden.

By lowering plant numbers over the harvest period there will be less weeds emerging the following autumn and lowering the pressure on herbicide products, such as ia knockdown prior to planting, a pre-emergent herbicide or an in-crop selective product.

The story Killing weeds at harvest first appeared on Farm Online.


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