Windrow burning fine-tunes weeds assault
GroundCover™ Issue: 113 | Author: Nicole Baxter
- Robert Gollasch uses integrated weed management to control wild oats and ryegrass on his farm near Wallacetown, New South Wales
- Narrow windrow burning, haymaking and a pasture phase have been adopted to drive down herbicide-resistant weed numbers
- Robert likes to burn narrow windrows early, before rain makes them difficult to burn
- A clean burn prevents carryover of herbicide-resistant weed seeds into following crops
New South Wales grower Robert Gollasch has adopted a long-term and integrated approach to manage weeds on his 2000-hectare farm
After continuously cropping some paddocks for 37 years, Robert Gollasch started narrow windrow burning when he realised he was running out of herbicide options to manage weeds on his property near Wallacetown, New South Wales.
Robert and his wife Liz crop 1800 hectares 23 kilometres north-east of Wagga Wagga. They started burning narrow windrows in canola four years ago and have made it a successful practice.
GRDC-supported research in Western Australia has shown destroying weed seeds by burning requires temperatures of 400°C (ryegrass) and 500°C (wild radish) for 10 seconds.
In wheat stubbles of three to six tonnes per hectare of biomass, soil surface temperatures of between 300°C and 400°C were recorded for between 30 and 50 seconds. These temperatures and durations increased with more stubble.
Although Robert sees narrow windrow burning as straightforward in canola, he has had mixed results in cereals.
“If everything is done correctly, narrow windrow burning works well, but if the burning is left until April the windrows can become wet, which is what happened to us this year,” Robert explains.
Robert says his narrow windrows in wheat only half dried even after four weeks of fine weather. At sowing after the windrows had been burnt, he noticed a “gooey residue” remained.
Although the residue “did not look pretty” it did not hamper crop germination. However, it did mean herbicide-resistant ryegrass weed seeds escaped in some areas, leading to a germination of ryegrass in parts of this year’s Hindmarsh barley.
By contrast, on four canola paddocks that were windrow burnt in late March, Robert successfully lowered the ryegrass seedbank.
When burning the windrows, Robert lights up about midday, with the aim of completing the job by 5pm. There is always a firebreak and a fire-fighting unit close by.
He says crops are harvested at a height of 150 millimetres to capture all the ryegrass and at harvest the windrows are about 300mm high but sink over time.
Robert allows his crossbred sheep to graze paddocks with windrows for a short period. Although the sheep “rough up” the windrows, he says this can help aerate and dry the residue.
Robert adopted narrow windrow burning after his consultant, Greg Condon of Grassroots Agronomy, suggested he try the technique.
He had also read articles in Ground Cover about WA growers who had fitted chutes to their harvesters to concentrate residues into narrow rows.
To build a chute for his Claas harvester, Robert designed a 457mm-wide outlet to prevent blockages.
However, he feels the chute is too heavy because two people are needed to attach the device to the harvester.
Going forward, Robert plans to make a lighter and narrower chute for easier handling.
By using a diverse crop rotation, Robert has the capacity to rotate herbicide groups to manage weeds.
He says he relies fairly heavily on pre-emergent herbicides such as Sakura® in wheat, which to date has controlled weeds successfully.
That said, he finds that barley is a difficult crop in which to control grass weeds, and this leads to a ryegrass build-up.
In one paddock where the ryegrass population was too high, Robert used two successive years of hay cutting to lower the weed burden.
Another strategy being tried is narrower row spacings. Robert recently bought a new seeding rig and moved from 305mm row spacings to 254mm spacings. While this was mainly to improve yields, he says the narrower spacings should also assist with weed control.
When a late October frost in 2013 wiped out 80ha of wheat on Robert’s low country, he took the opportunity to clean up the weeds by cutting the area for hay.
With 10 per cent of land under lucerne, Robert also uses the pasture phase to drive down the ryegrass population.
To bring paddocks back into crop, a single application of glyphosate, 2,4-D amine, Ally® and Lontrel® has been used to eliminate weeds. Another dose is sometimes needed to take out difficult-to-kill lucerne.
Robert has not ruled out green and brown manuring with field peas or lupins if the weed population increases.
More information:Robert Gollasch,
0418 695 862,
0428 477 348,
Region South, West, North