WHILE the cropping sector is united on the benefitsof harvest weed seed management (HWSM) there are still a number of different methods to achieve the outcome of running down the weed seed bank at harvest time, each with their own distinctive advantages and disadvantages.
A panel of growers at last month's WeedSmart conference outlined the different tactics HWSM tactics they were using to keep weed numbers in check.
Pingelly, WA, farmer Lance Turner said he had been implementing some sort of HWSM for around 15 years when he first started using a chaff cart.
From there he moved onto a Harrington Seed Destructor, but he said the problem of burning the residue remained a problem.
"The burning would take forever," Mr Turner said.
However, he said the benefits to the farm business meant it was worthwhile.
"We've got a low weed burden, we still use a lot of trifluralin, via nozzles on the bar, and we also get great effectiveness from older herbicides such as MCPA and diuron, we can control broadleaf weeds at three leaf stage for $3.5 a hectare, so not letting weeds get up and evolve resistance is a winning strategy for us."
"Across the farm we've never used (higher cost pre-emergent product) Sakura, so we're keeping those chemical bills down."
Mr Turner said he had identified fallow paddocks as potential weak links in the weed management system in years to come.
At Lameroo, SA, Robert Pocock said chaff carting was were working well.
Initially he said the farm had been narrow windrow burning but he got sick of losing the crop residue in an area with already low soil organic matter.
From there he moved into chaff lining where he said there were more problems with volunteers as the chaff did not break down and mulch properly.
"It was mainly cereal volunteers that were the problem, the legumes were easy enough to blow out with something like amine," Mr Pocock said.
"We had wheat in barley and vice versa it just got messy."
"The chaff cart is working OK and creates a valuable by-product in terms of sheep feed, if that chaff was just blown out the back the sheep wouldn't find it but they can keep going on chaff piles for some time."
Tim Paschke, who farms at Waikerie, in the SA Riverland, with just 250mm annual rainfall, also uses chaff carts.
"We have light sandy soils and it is pretty marginal so keeping herbicide costs down is essential," Mr Paschke said.
"After continuous cropping up until 2010 we had lots of weeds coming up and by 2012 I'd seen chaff carts on the internet," he said.
"With chaff carts and the use of imi herbicide tolerant lines we've been able to virtually eliminate brome grass, with a vetch, canola and Clearfield wheat rotation.
However, he said there was still work to be done.
"Rye is really tough one to control."
He said burning chaff piles could be problematic.
"If there is no wind they can just smoulder and smoke for days, we now try to burn on days where there is just a hint of breeze to help them burn."
He said they were now investigating more chaff dumps, as like Mr Pocock, he found them a good source of livestock feed.
"In 2018 we had no rain but we kept 1000 Dorpers and their 1500 lambs alive on chaff dumps."
"It's definitely something that has merit but equally we won't do it on everything."
Mick McClelland, Sea Lake, Victoria, is using chaff lining as his main form of HWSM.
"It goes well, but it is only as good as much you can get in the cutter bar," Mr McClelland.
"In droughtier years I have thought I have got it all and laid it into thin chaff lines, but in other years the brome grass seeds have already shed, they can be pushed under the front in high production years," he said.