Rhys and Joel Curr, Trundle NSW

A broadleaf crop double-break is keeping grass weed numbers down for the Curr family as they expand their area of cropland and complete the transition out of livestock production.

Brothers Rhys and Joel and their partners farm with their parents, Andrew and Belinda Curr, on a 5800-ha aggregation of owned, leased and share-farmed blocks within a 45-km radius near Trundle in the Central West of NSW.

Although Andrew and Belinda found benefits in their mixed farming system, Joel and Rhys felt that the sheep were too time-consuming for the returns they brought.

“We wanted to focus on grain production for ease of management and higher returns,” says Rhys. “The last of the sheep were sold in 2023, freeing up more time to spend growing the best crops possible.”

Although the sheep played a part in weed management by reducing seed set on summer fallow weeds, they didn’t kill the weeds. With no sheep in the system, the Currs are doing more summer fallow spraying and using a double break phase to clean up winter weeds.

Rhys says the whole aggregation is managed much the same, regardless of land ownership. In this 450 mm rainfall zone, the Curr’s most problematic weeds are heliotrope, fleabane, windmill grass, crop volunteers and some thistles in summer and annual ryegrass, wild radish, wild oats and windmill grass in winter.

WeedSmart Big 6 in action

#1 Diverse rotation

The Currs run a winter cropping program that begins with a legume crop (vetch, lupin or field pea) followed by canola before moving into a cereal phase of wheat, barley, wheat. They have implemented a block farming system that includes 2000 ha wheat, 1000 ha barley, 600 ha vetch, 1000 ha pulse (lupin and field pea), and 1000 ha canola most years. Rhys finds this rotation works well in their locality, although canola can struggle in drier years.

“The legume followed by canola provides a double-break for grass weed control and allows us to target problem weeds, like wild oats with resistance to Group 1 fop chemistry,” says Rhys. “We grow vetch as a brown manure because it provides multiple benefits to our cropping system.”

The vetch brown manure is good for soil health, provides a longer fallow for weed control and provides about 200 units of fixed nitrogen, sufficient for the following canola crop. This results in significant savings in their fertiliser expenses across the business.

“We spray out the vetch in September and leave the crop residue in place to increase rainfall infiltration and conserve soil moisture over summer,” he says. “We spray any summer weeds that emerge, and the crop residue is easy to plant through in the next season.”

On their share-farmed and leased blocks, the Currs don’t implement the brown manure phase but rather grow a narrow leaf lupin or field pea crop ahead of canola. Wherever possible, they avoid planting wheat on wheat.

“Growing grain legume crops for harvest is also very beneficial to our rotation,” says Rhys. “We still gain soil health benefits, including slow-release soil nitrogen. As a result, the following canola crop requires only about 50 units N to compensate for the nitrogen removed in the lupin and field pea grain. Regardless of the pulse crop grown, the following canola yields are up around 3 t/ha, and the yield is always higher than if canola follows a cereal.”

Canola relies on good soil moisture through the profile, so the Currs don’t plant if there is insufficient moisture. In their region, this happens about 1 in every 6 years, and they usually grow a cereal crop in these drier years instead. They currently grow hybrid TT canola varieties, HyTTec Trifecta, HyTTec Trophy, and Hyola TT Blazer, and would consider growing Clearfield canola varieties in the future.

#2 Enhance crop competition

By building up the soil nutrition using legumes, reducing compaction with controlled traffic farming and addressing soil constraints, the Currs are increasing the competitiveness of each crop against weeds while optimising grain yield.

“We have been doing the brown manure vetch for more than four years and have noticed a significant saving on nitrogen fertiliser across the operation,” says Rhys. “We have mapped the farms for pH levels and phosphorus deficiency and are addressing soil constraints with lime, gypsum, sulfur and phosphorus as required using variable rate applications. We are deep-ripping the sodic areas and incorporating the gypsum.”

They have a 5-year plan to shift pH from around 5 up to 5.5 with surface applications of lime at variable rates. Phosphorus is applied at variable rates through the air seeder, and urea is applied to each block according to soil test recommendations.

Andrew started the transition to controlled traffic farming in 2010, based on 3 m centres for all their machinery and 12.1 m trams.

“CTF has made a huge difference to how we farm,” says Rhys. “Having soft soil for the crops to grow in and compacted tramtracks for the machinery means the crops can grow deep root systems to access nutrients and moisture, and we can access the paddocks soon after rain.”

Their controlled traffic farming system resulted in 70 to 80 per cent of their paddocks being sown east-west. Research in Trangie, NSW and WA has shown that crops sown east-west in more southerly latitudes are more competitive against weeds. In Western Australia, Department of Agriculture and Food researcher Dr Catherine Borger demonstrated in six trials that east-west sowing can halve annual ryegrass weed seed set, even though weed biomass may not be reduced.

“Stubble retention is critical to provide ground cover and conserve soil moisture over summer,” says Rhys. “We aim to grow as much biomass as our rainfall allows, and there is stubble evident on the soil surface from the previous three or four crops. But, there is less stubble bulk left in the Trundle region than in cooler and higher rainfall areas.”

Having previously used a tyne seeder on 300 mm spacing, they have recently changed to a disc seeder, which was not previously an option on their red loam soils when the sheep were grazing stubbles. Their NDF disc seeder is set up on 254 mm (10 inch) row spacing, and they are pleased with how well the crop residue in their stubble retention system flows through. Also, weed germination is less than with the tyne seeder.

The Currs use three canola varieties with different optimal planting times to extend their sowing window for easier logistics and to disrupt weed populations that might be shifting their seed dormancy and evading pre-emergent herbicides.

#3 Spray efficacy

At this stage, the Currs are not using optical weed detection in fallow, but they are considering getting a contractor to assist with managing patches of hard-to-kill windmill grass. For now, they are cultivating patches of windmill grass straight after harvest to stop weed seed set and prevent large plants from establishing over summer.

During summer, they aim to apply knockdown herbicides 14 days after rain, and it takes them 2.5 to 3 weeks to get around the farms.

“It gets very hot and windy here in summer, and it is difficult to get across all of our area as quickly as we would like,”says Rhys. “But there is no point spraying when the conditions will seriously affect the efficacy of the herbicides being applied.”

“There are cotton crops within 30 km of our farms, so we are cautious with spraying during the cotton season,” says Rhys. “We use a hand-held wind meter to assess conditions in the paddock and don’t spray if an inversion is present. We don’t do much night spraying either.”

Rhys and Joel keep their water rates high to maximise herbicide coverage and plant uptake. They aim for the upper water rates on the product label, such as 65 L/ha for glyphosate and 100 L/ha for paraquat for summer spraying, and 80 to 100 L/ha water for Mateno Complete.

On their owned farms, they pump water from farm dams into storage tanks where silt and clay particles can settle before the water is used for spraying. They use ammonium sulfate to soften the water and improve herbicide uptake. They also use recommended adjuvants such as Li700 for summer weeds and Hasten in canola sprays, being aware that many products have adjuvants included in the formula.

“We have a chemical trailer set up to carry two pallets of dry product, four shuttles of liquid product, and an 800 L batching plant,” says Rhys. “The SP sprayer tows the chemical trailer to the block being sprayed to increase our time efficiency. It takes 12 to 15 minutes to fill the sprayer using the sprayer’s taps and shuttle systems, which also reduces the operator’s exposure to the chemicals.”

The Currs employ the services of a consulting agronomist who monitors their farms for weeds every two weeks.

“We use the AgWorld farm management software to communicate with each other and our agronomist,” says Rhys. “It is a good way to store our spray data and our agronomist’s notes on weeds and any resistance issues for the team to see. We also use it to plan our herbicide program.”

#4 Mix and rotate herbicide MOA

The Curr’s farm business consultant, Rob Patterson from Rural Management Strategies (RMS) in Cootamundra, advises them on all aspects of their business, including their chemical program and crop rotation. They appreciate the value of the advice that considers their overall budget to plan a profitable and efficient program to produce optimal yield crops.

“Our farms have had less herbicide use due to the mixed farming history, which has helped to delay herbicide resistance,” says Rhys. “Now that we are 100 per cent cropping, we are trying hard to keep our rotation and herbicide use as diverse as possible.”

The Currs use glyphosate (2 L) plus a spike of Terrad’r (tiafenacil, Group 14, for grass and broadleaf control) followed by paraquat (2 L) plus Hasten as the double-knock pre-seeding tactic to give their crops a weed-free head start wherever possible. The 2024 season allowed for a double-knock with spikes across the whole area before sowing and resulted in excellent weed control. This is particularly important in a disc seeding system with limited pre-emergent herbicide options.

They use Lontrel in canola and cereal crops for residual control of broadleaf weeds such as fleabane. In pulses, a successful pre-seeding double-knock is crucial because Lontrel can’t be used.

Growing TT canola hybrids allows the use of triazine herbicides post-crop emergence once weeds grow above the stubble layer.

In the cereal phase, more pre-emergent herbicide options are available to rotate, and they still have access to several in-crop herbicides for grass and broadleaf weed control.

The Currs have submitted weed seed samples sent for herbicide resistance testing, initially after clodinafop (Group 1, Topik) failed to control wild oats. They have also tested annual ryegrass, which had medium resistance to pinoxaden (Group 1, e.g. Axial). However, Axial still works well for wild oats and remains in their program.

Rhys says that now that they are cropping their land more intensively, they expect that more instances of herbicide resistance will arise, but they want to slow the process as much as possible by being proactive with their weed control program.

“The brown manure phase is a key component in our program to keep weed numbers low,” says Rhys. “We are doing our best to maximise the efficacy of each herbicide we apply, like using mid to high range label rates for most products, keeping water rates up and spraying when conditions allow the herbicides to work well.”

#5 Stop seed set

The double-break is a proven tactic for reducing the annual ryegrass seedbank. When the Currs started using the vetch brown manure tactic a few years ago, they didn’t apply any grass herbicides while the vetch was growing. Rhys says they noticed that this resulted in the establishment of some large grass plants in the vetch that either set seed before it was time to spray out or were too large for the double knock to kill completely.

“We were putting too much pressure on the double-knock at the end of the vetch phase, so now we spray clethodim during the growing phase of the vetch to stop the grasses setting seed and ensure that any grass plants present at the end of the vetch season are small,” he says.

The Currs croptop their barley and lupin crops when required to stop seed set on late germinating weeds. They also windrow their canola, or desiccate it as an aid to harvest in the years that they can’t windrow.

“We use our own windrower to get the job done when the timing is right,” says Rhys. “We windrow as high as possible, so we know we are not putting much weed seed into the canola windrows. We plan to start spraying glyphosate under the cutter-bar to initiate fallow by killing those late-emerging weeds, particularly targeting early germinations of windmill grass and flowering ryegrass. If the windmill grass population increases, we cultivate those areas early in summer.”

Since wrapping up their sheep operation, the Currs have removed about half of their fences. The remaining fencelines are sprayed with glyphosate plus Terrain or Terrad’or in June after the weeds have germinated.

To reduce the risk of weeds entering the cropping area, each paddock ends with a road that the drag bucket keeps weed-free. Along the sides, crops are sown right to the border and in-crop herbicides are applied right to the paddock’s edge, including the fence line if there is one.

The last five years have been a period of rapid expansion for the Currs as they bring the pastures into cropping. This has involved a lot of cultivation, which has reset the weed seed bank. Rhys and Joel hope that the cropping system they are putting in place will reduce the need for cultivation going forward.

#6 HWSC

The Currs have used narrow windrow burning as a harvest weed seed control tool in the past, but they are looking into other options now that they are less reliant on harvester contractors.

“We run two of our own headers and plan to use the same system on both machines,” says Rhys. “We are leaning towards the chaff deck system for the added advantage of suppressing dust on the wheeltracks for summer spraying. The chaff decks are also compatible with a disc and stripper front system that we are moving toward.”

The Curr’s pulse plus canola double-break provides multiple benefits to their farming system.