Risk management focus changes approach to weed management

After adopting the typical reactions to escalating herbicide resistant weeds, including a range of herbicide and weed seed management strategies, Rob is now looking to farm smarter and return to a strong focus on sheep in the program, especially with the improved returns for livestock commodities.

Rob manages the 5000 ha ‘South Gum Creek’ property near Farrell Flat, east of Clare in the Mid North, cropping 2830 ha to wheat, barley, export oaten hay and for sheep feed, and mating 5500 ewes to Merino and Suffolk sires.

The farm is in a 400 mm rainfall zone, but received around 600mm last year, helping to produce some of its best ever crop yields. In recent years, typical rotations on the mostly heavy red clay soils have included wheat-barley-canola-export hay and wheat-barley-export hay-sheep feed.

“Chemical resistance has been our biggest issue. We were continuously cropping, but we are not doing that anymore. It got to the point where we were not beating weeds. Now with higher numbers of livestock in the rotation, I can drive past a dirty paddock and say: ‘that will be sheep feed next year’,” Rob said.
“We were managing it over the years, but it was getting worse. We were doing double knocks and we used to burn canola rows.

“We have spraytopped canola and we spraytopped some barley last year. We have also spraytopped wheat, but I don’t think this works well and I am also concerned about the overuse of glyphosate.

“ We were spending a lot of money and not really getting in front of our weed control. We are now looking at the weeds another way and we keep coming back to the sheep. The livestock returns are good and give us another option for our weed management.”

“We are trying to take the risk out of things with livestock. With cropping, you need to get bang for your buck the with high cost of machinery, fertilisers and chemicals.’’

He said export hay, which they produced on 500 ha in 2015, was hard work, but it was the most important tool for weed seed management.

They also now apply one knockdown of Roundup^® with a spike of Goal^® or Striker and have been using the Group K pre-emergent herbicide, Sakura^® 850 WG from Bayer, since it became available.

Comprising the active ingredient, pyroxasulfone, Sakura controls annual ryegrass, barley grass, silver grass, annual phalaris and toad rush and also suppresses wild oats (black oats) and brome grass in wheat (not durum wheat), triticale, chickpeas, field peas, lentils and lupins.

“We use it everywhere with our first wheat crops in the rotation,’’ Rob said.

“We were using Treflan^®/Avadex^® (Xtra) and Boxer Gold^®, but Sakura is working for us right now as a tool to limit our ryegrass. It’s about population management and Sakura is now managing it.

“In the second year we could go to hay and then back to wheat with Sakura in year three. We can get the population down quite low and then we are getting great control with Sakura – it could be 90-95% control.

“If we go with wheat again in the second year, we will apply Boxer Gold, and if it’s barley, it might be metribuzin.

“Sakura picks up a bit of brome grass as well and if I’ve done a paddock with Sakura, I don’t have to go back into it again, except for ‘broadies’ (broadleaf weed control). In Boxer Gold paddocks, we have to go back in again with another grass spray, so we have significant extra cost in Boxer Gold paddocks where we are doing that.’’

Sakura is incorporated by the farm’s 16.5-metre (55-foot) Bourgault Paralink seeder featuring a single shoot system with knife points and press wheels.

“We quite often start with putting in the sheep feed in mid-April and last year we sowed dry with Sakura, then we had rainfall and it worked well,’’ Rob said.

“We have had following rains with the Sakura most of the time and it has worked well – and the paddocks have generally come off two years of sheep.’’

Rob coordinated a trial on the property in conjunction with Bayer last season to investigate pre-emergent grass control treatments in wheat.

The replicated plot trial compared Sakura with prosulfocarb and in mixtures with triallate in a high grass weed population section of a paddock that had previously produced two export hay crops.

Rob said they compared the plots visually during the season and while grass numbers in the Sakura treatments were largely non-existent, numbers then increased in the other plots and were high in the untreated plots.