Read time: 5 minutes

Can a diverse farming system be profitable and hard on weeds?

with Tony Swan, farming systems researcher, CSIRO

Results from over a decade of farming systems research have illustrated that many factors need to be considered and implemented for a cropping enterprise to be profitable, manageable, and to minimise risk. 

Tony Swan, a CSIRO farming systems researcher, says that decisions related to weed control vary depending on the crop rotation implemented. Multiple factors, including stubble management, nitrogen use, grain storage, and machinery cost, influence the profitability of the rotation.

“Field trials often focus on one or two critical factors, aiming to understand the effect between treatments,” he says. “It is important when conducting trials at a small plot scale, that the researcher, agribusiness consultant and the grower are confident the results can be scaled up to commercial ‘whole farm’ level.”

With a large body of research findings on a wide range of weed management strategies, crop rotations, and stubble management options in the southern NSW region, the multidisciplinary team scaled up the results and tested them in real-world scenarios for farms with 3000, 5000 and 10,000 ha of crop.

“For example, when it comes to planting equipment, irrespective of opener type, we found no difference in the profitability or effect on weed numbers where more expensive herbicides were used,” says Tony. “Tyned openers were more effective when lower-cost herbicides, such as trifluralin, were used, mainly because fewer of these herbicides are on-label for a disc opener.”

Growers who implement the WeedSmart Big 6 strategy, which includes both herbicide and non-herbicide tactics, should be able to achieve high profitability while keeping the weed seedbank low.

This year, Geraldton is hosting WeedSmart Week on 29 and 30 July, showcasing how growers can develop a profitable farming system using the WeedSmart Big 6 framework to make sure that weeds are not calling the shots.

What are the keys to good stubble management for weed control?

Zero-till, stubble retention and fallow weed management have been widely adopted in Australian cropping systems – and for good reason. In combination, these farming system practices protect the soil from erosion, aid in moisture infiltration and storage, and reduce weed numbers in fallow.

However, it is important not to let heavy stubble compromise the timeliness of operations or hinder weed, disease or pest management. A stubble load of 2–3 t/ha (i.e. 70% ground cover) is enough to achieve erosion control and water infiltration outcomes. 

If the stubble exceeds 3 t/ha, consider using any of these post-harvest management tactics to reduce the load: mulching, incorporation+nutrients, baling, grazing or late strategic burn (especially before a second wheat crop or before sowing canola). Including a legume in a diverse crop sequence will help manage stubble, improve nitrogen efficiency and assist in converting the cereal stubble into organic carbon.

Cereal stubble is a good source of carbon (C) but provides very little nitrogen (N) for subsequent crops. Therefore, when stubble is retained and incorporated, there can be significant N tie-up. To compensate, in a canola-wheat rotation, apply deep band N and add 5 kg N/t of cereal stubble at sowing. Alternatively, sow a pulse legume, such as faba bean, lentil, chickpea or vetch, into the wheat stubble, followed by a canola crop.

From a weed management perspective, be flexible and proactively manage stubble to suit your seeding system. Both tyned and disc systems are equally effective for weed management and crop performance when stubble load is managed appropriately to allow for diversity in pre-emergent herbicide use.

What is an effective rotation to keep annual ryegrass numbers low?

Initial testing of weeds for herbicide resistance is crucial to determine the most appropriate herbicide and the best management options available. A crop rotation that includes a double-break of two non-cereal crops, such as faba bean-canola or vetch-canola, was found to be the most effective tactic for reducing herbicide-resistant annual ryegrass numbers.

A ‘diverse-low-value’ system (low-N, faba bean-canola-wheat) that includes a pulse crop in either a 3- or 4-year sequence matched or improved the profitability and reduced the financial volatility compared to the ‘baseline’ systems (canola-cereal-cereal) at both the small plot and whole-farm scale.

Where there is an existing annual ryegrass weed issue, the ‘diverse mix’ systems (low-N, vetch hay/BM-canola-wheat) where pulse crops can be brown manured or cut for hay may be more profitable than a ‘diverse’ system with a pulse grain crop, depending on how the resistant weed is managed. The combination of experimental and whole-farm data supports the agronomic value of including a pulse crop (e.g. faba bean, chickpea, lentil, vetch) in farming systems in southern NSW.

What other management systems need to be in place?

The profitability and sustainability of this system rely on the farming enterprise having adequate machinery and labour resources in place.

When scaling up to the ‘whole-farm’ for a cropping operation that incorporated legume crops in the rotation, it was apparent that factors such as on-farm storage for pulse grain and adequate machinery and labour resources were critical to the profitability of the farm and the subsequent effectiveness of the weed-suppressive cropping program.

The economics easily stacked up for new grain storage facilities to enable better marketing of pulses such as lentils, chickpeas and faba beans. On the other hand, the rapid increase in machinery costs made it difficult to justify the investment in machinery for more timely operations. The recommendation is to carefully consider purchasing quality second-hand equipment.

GRDC code: CSP1306-003RTXCSP1703-007RTXCSP2110-004RMX

More resources

Related Articles

Related Articles

View all
Article
Ask an Expert

Navigating precision agriculture for weed control

There are technologies and systems that have the potential to achieve gains in each of the six pillars of the WeedSmart Big 6. Read More...
Article
Ask an Expert

Killing weeds and staying below maximum residue limits

Steven Tilbrook, agronomist with the CBH Group in Western Australia, says that two of the greatest risks to Australian grain markets are weed seed contamination and chemical residues. Read More...
Article
News

Keeping weed numbers low pays off

CSIRO’s Jackie Ouzman, says growers’ investment in weed control is minimising yield losses from residual weeds growing in crops and fallows. Read More...

Webinars

View all
Video
Webinar

Managing fenceline weeds (and avoiding resistance!)

Jana Freebairn to discuss fence line weed resistance trends, and how they are best managed through herbicide and non-herbicide options. Read More...
Video
Webinar

Achieve effective pre-em weed control while protecting the crop at seeding

Greg Condon discusses the role of pre-emergent herbicides with ICAN's herbicide technology expert Mark Congreve and FMC's tech specialist Mark Yerbury. Read More...
Video
Webinar

Spot Spray Technology — advantages & opportunities incorporating the latest camera/optical spray equipment

We discussed the latest spot spray technology on offer. Read More...

Videos

View all
Video
Video

Targetted tillage for inter-row weed control

Inter-row targetted tillage prototype reveal, Mar 2025, featuring the research team: Dr Michael Walsh, Dr Stuart Watt and Dr Andrew Guzzomi. Read More...
Video
Webinar

Managing fenceline weeds (and avoiding resistance!)

Jana Freebairn to discuss fence line weed resistance trends, and how they are best managed through herbicide and non-herbicide options. Read More...
Video
Webinar

Achieve effective pre-em weed control while protecting the crop at seeding

Greg Condon discusses the role of pre-emergent herbicides with ICAN's herbicide technology expert Mark Congreve and FMC's tech specialist Mark Yerbury. Read More...

Factsheets

View all
Fact Sheet

Research paper: Diverse systems to manage herbicide-resistant annual ryegrass

High levels of control (>95%) over 3 consecutive seasons can reduce ARG seedbanks. Diverse crop sequences are the most cost-effective method. Read More...
Fact Sheet

Impact of weeds on Australian grain and cotton production

Weeds are one of the most significant costs to Australian grain and cotton producers, costing $4.4 billion annually, or an average $206/ha. Read More...
Fact Sheet

Research paper: 2013 to 2017 random surveys for herbicide resistant grass weeds

Frequency of herbicide resistance in wild oats, brome grass and barley grass as determined by random surveys across south-eastern Australia. Read More...

Subscribe to the WeedSmart Newsletter