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Michael & Marnie Fels, Wittenoom Hills WA

Crop competition and rotation keep weed numbers low

Cultural weed control has been a major focus for Mic and Marnie Fels on their Wittenoom Hills property, 50 km north of Esperance WA.

The resulting low weed numbers mean they can still use a range of ‘older’ off-patent herbicides, which helps keep herbicide costs to a minimum.

“We have tried to use herbicides as a backup for our cultural practices, rather than the other way around,” says Mic. “Narrow rows, stacked rotations and chaff lining all crops at harvest are the central components to our weed management, taking the pressure off our herbicide program.”

Noticing the early stages of triazine resistance in annual ryegrass was a significant motivator for implementing their weed management program, and Mic is pleased that their actions have ‘saved’ this valuable herbicide option.

“We bought this farm in 2002, having always farmed in the district, and although some of the older Group 1 [A] and 2 [B] herbicides are gone, we have all other options, including triazine, and still get good results using the ‘old rates’.”

Mic and Marnie’s farming system is an excellent example of the Weedsmart Big 6 in action – incorporating a range of herbicide and non-herbicide weed control strategies.

Narrow row, high residue seeder

In 2011 Mic changed the row spacing from 30 cm (12 inches or ‘ryegrass heaven’) to 18.75 cm (7.5 inches). Any gap in the crop reminds Mic what a big difference narrower row spacing has made to their weed control.

In changing to narrower row spacing, Mic wanted to change from a tined to a disc seeder but was not 100 per cent happy with the disc seeders available. Being an engineer, he set about modifying a John Deere seeder, which led to the development and commercialisation of his own disc seeding design, now marketed as the i-paddock Alpha disc seeding system.

“The seeder units have a single rippled disc rather than the traditional flat disc and no gauge wheel. This combination achieves better soil throw into the inter-row and eliminates blockages from mud. The improved soil throw is very important when using pre-emergent herbicides and for crop establishment on non-wetting soils.”

“The result is a simpler machine with fewer components – just a disc, a seed boot and a press wheel,” says Mic. “Planting is a smoother operation with far less downtime or choking up with stubble.”

“Setting the harvester choppers to spread the stubble evenly is very important and can be difficult to do on older harvesters,” he says. “But accurate seed placement relies on even stubble spread, so it is worth doing what you can to achieve this at harvest.”

In 2020, Mic released a new model of his i-paddock Alpha Disc, with hydraulic downforce and parallel lift, fitting the units to a custom-built 24 m toolbar mounted to a 25,000 L Simplicity aircart. The 24 m i-paddock machine sows 128 rows on 18.75 cm spacing and operates at 14 km/hr, sowing at around 32 ha/hr.

The hydraulic parallel lift allows each unit to independently follow the ground surface, avoiding the need to articulate the bar, simplifying the overall design.

Wet years have less impact

The 2016 season was unusually wet, and the Fels compare it to 2003, their second season farming at Wittenoom Hills, but they have been pleased to notice a big difference in the effect of wet weather on weed numbers.

“In 2003, we had such a large area infested with ryegrass that we were forced to salvage paddocks to hay,” says Mic. “This made us realise that weed management had to be a priority, and we have put as many cultural practices in place as possible to lessen the effect of wet years where herbicides are not enough to cope with the ryegrass pressure.”

“Another cold and wet winter in 2016 thoroughly tested our system, and ryegrass was only an issue where the crop basically died from waterlogging. Crop competition is just so important in this environment.”

After two decades, the Fels still have most of the older chemistry available and all the new chemistry options up their sleeve.

The Fels are now working on building soil nutrition to complement the narrower row spacing. They have increased phosphorus rates to support strong early growth to achieve strong crop competition. They are now measuring soil carbon on-the-go using a seeder-mounted Veris iScan unit to better understand the impact of their farming system on soil carbon levels.

“We were struggling with nitrogen tie-up for a few years as our residue levels increased and yield potential increased together, and it showed in our grain protein levels,” says Mic. “For efficiency and economy, we use broadcast urea as our nitrogen source, with one application soon after seeding, and the next usually in July or August. We are increasing our nitrogen rates as we see our system achieving new yield benchmarks every season now.

Mic targets 10.511 per cent protein in his cereals and 43 per cent oil in canola, as an indication that they have fertilised correctly to their potential yield. He is now consistently achieving these targets, using the ipaddockYield app to set their late season nitrogen top-up rate.

“We are seeing some really good N-use efficiency numbers now, even with our very high residue levels. I think the N is starting to cycle through our retained stubble and soil organic matter now.”

“Residue retention, improved system robustness and nitrogen have all been pivotal, and the combination has increased our yields by over 1 t/ha over the last decade, which is quite staggering.”

Responsive rotation

What started as an effective disease management system, stacked rotations and stacked phases within the rotation, has had long-lasting effects on weed management.

Until recently, we used a stacked rotation that involved growing each of our three crops – canola, wheat and barley –for two consecutive years each rather than spreading them out in the rotation,” says Mic.

The result was a four-year break for the diseases that affect each crop, namely black leg and sclerotinia in canola, crown rot in wheat and net blotch in barley. Mic says the system eliminated crown rot, which was once a significant challenge on the farm.

Although this tactic worked well for Mic and Marnie, most plant pathologists have reservations about the disease risk involved, particularly in the canola phase.

“With the double canola, we always made sure we used two different blackleg resistant varieties, and we never saw any blackleg or Sclerotinia using that system.”

Unfortunately, the four consecutive years of cereal crops allowed grass numbers to build up again. Mic has now adapted their rotation to a more traditional canola–wheat–barley rotation, and added lupins to stack behind the canola for a 2-year grass weed break when conditions allow.

“Rotations seem always to be a work in progress here, but with the robustness of our whole system now and the efficacy of the new generation pre-emergent cereal herbicides, the more traditional rotation seems to be working well for us again.”

Mic uses all the cultural and herbicide practices available in canola, aiming for 100 per cent ryegrass control to set up the rest of the rotation with very low weed numbers. Since switching back to a tighter rotation, combined with their high residue cropping system, there is usually too much cereal residue to burn canola windrows safely.

Since selling their cattle in 2012, Mic and Marnie have grown very few legumes in their crop rotation. They had previously undersown Clearfield canola with lucerne to establish solid stands of the perennial legume for minimal cost. Mic is now bringing lupins back as their legume of choice, and is excited to see new export options with good pricing for lupins now in Esperance.

Chaff composting

Mic uses chaff-lining as their harvest weed seed control strategy, funnelling the weed seed-laden chaff component into a narrow strip behind the harvester.

In their controlled traffic system (CTF), the weed seeds collected through the harvester are concentrated in the same zone every year, and any seeds that germinate through the mulch are subject to the full force of crop competition. Similar to the experience of growers using a chaff deck to channel chaff into CTF permanent wheel-tracks, Mic finds that the chaff and the weed seeds rot away, and there is no need to burn the chaff to gain the benefits of this weed control measure.

Mic views chaff-lining as ‘an incremental tactic’, accepting the fact that a portion of the annual ryegrass seed will already be on the ground at harvest. Over time though, he says the results are obvious when harvest weed seed control is implemented in every paddock every year.

“For us, chaff-lining works well. It only costs $200 for a plastic chute for the harvester, and there are no moving parts to break or slow us down,” he says. “While early cutting is important, it can’t be done across the whole farm, especially in wheat, so you must accept that some paddocks will be harvested too late for optimal weed seed capture.”

“Even so, more and more weed seed is captured and composted in the chaff lines every year,” he says. “And you can still drop the front that bit lower when harvesting a grassy section in a paddock.”

In 2022 the Fels switched to 18 m harvester fronts, which creates thicker chaff lines that may pose some issues at seeding. Ultimately, Mic wants to move towards a kill-and-spread solution for the chaff, but is worried about current mill options slowing the harvesters down in what is already a difficult harvesting, south coastal environment.

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