Jan 10

Summer moisture preservation is critical

Posted by Kylie Dunstan at Friday, January 10, 2020

The following article appeared in the Summer 2019 edition of the FarmLink quarterly member-exclusive publication The Link (archives appear at

While it might be tempting to allow weeds and crops that have been cut for hay or windrowed to regrow as a source of livestock feed, the impact on following crop yields could be significant.
Riverina Independent Agronomy consultant Neil Durning says weedy canola crops are ideally sprayed before windrowing to reduce the addition of ryegrass to the seedbank and a loss of moisture and nutrients from the soil.
“As part of an integrated weed management plan, it is worth applying glyphosate to canola with ryegrass from early senescence at label rates,” he says. “One way or another you want the canola and the ryegrass dead. It doesn’t take much rain for ryegrass to stick a head out and add more seeds to the seedbank.”
Mr Durning says wheat following canola where glyphosate was applied before harvest appears to hang on for longer in dry finishes. Spraying before windrowing also reduces the likelihood of plant regrowth after rain.
3D-Ag consultant Peter McInerney advises his clients against grazing sheep on paddocks that have been cut for hay.
“Do not try to retrieve residual grazing from hay paddocks because there is none to be had,” he says. “All you will do is powder the soil and have it blow away, particularly paddocks that have been cut for hay for two consecutive years.
“A crop that would have produced 2.5t/ha of grain leaves 3 to 3.5t/ha of residue. That same paddock cut for hay will leave behind less than 1t/ha of residue.”
Where hay has been cut for two consecutive seasons, Mr McInerney encourages the application of manure to replace lost organic matter and nutrients.
Effective summer weed management is critical to reap the soil water conservation benefits of retained crop residues (Flower, Dang & Ward 2019).
Zeleke (2017) showed that summer weed control increased residual soil water and soil nitrogen by 64 millimetres and 60 kilograms per hectare respectively.
Lilley and Kirkegaard (2007) used modelling to show that summer weed control could increase subsequent wheat yield by up to 20 per cent.
According to NSW Department of Primary Industries researcher Colin McMaster ( trials in Central New South Wales showed the economic benefit of every dollar per hectare spent on herbicides to control summer weeds was $8/ha.
Mr Durning says mixed farmers must treat weeds as if there are no livestock in the system, particularly if the paddock is earmarked for cropping.
“The minute you compromise on summer weed control by allowing weeds to grow large is when you start to reduce the yield potential of next year’s crop,” he says. “Preserving moisture over summer is the difference between having a crop that can be harvested and salvaging a failed crop in a dry finish.”
John Stevenson allows sheep to lightly graze stubbles on ‘Orange Park’ near Lockhart only after the first summer knockdown has been applied. His actions back research showing grazing sheep on crop residues at low stocking rates has no detrimental impact on following crop yield (Hunt et al. 2016, Allan et al. 2016).
Where paddocks are bare, Mr Durning says a strategic cultivation may be needed to curb erosion and maximise water infiltration, although this depends on slope and implement choice. Cultivation leaves the surface coarse and lumpy to slow run-off and reduce surface wind speed.
Mr Condon says one of his clients with discs on 16.5cm row spacings planted millet over summer as a cover crop.
“It was sprayed out at early tillering and we saw no yield loss in the following crop even in a dry season,” he says. “You have to be disciplined to avoid grazing and spray it out before the roots reach 15 to 20cm deep to prevent stored soil water loss.”
While two to three tonnes of wheat stubble per hectare (Kirkegaard & van Rees 2019) or 70 per cent soil cover are suggested to minimise erosion and maximise water infiltration, Mr Condon suggests keeping 100 per cent of cover if possible.
He and Mr McInerney agree that confinement lots are worthwhile to preserve soil cover. Confinement lots work on the theory that less topsoil is lost by concentrating sheep in a small area rather than a large area.
Mr McInerney suggests positioning a new confinement lot near an existing tree line where there is standing crop and to apply for grants for infrastructure needs.
Mr Condon says confinement lots allow sheep to be efficiently kept at target condition scores using grain and straw, while preserving soil cover.
“My clients with diverse rotations who kept stubble from 2016 have produced reasonable crops during the past two years,” he says. “The retained stubble allowed autumn rain to infiltrate rather than run off and enabled crops to be established on time.”
Mr Durning agrees, adding that he has noticed paddocks with less stubble cover failed two weeks earlier this year than paddocks with a higher percentage of cover.
Acknowledgements: Peter McInerney, Neil Durning, Greg Condon and John Stevenson.

Nov 01

Wanted: Wild Radish Seed

Posted by Cindy Cassidy at Tuesday, November 01, 2016

FarmLink, in conjunction with Bayer, is looking for 20 wild radish seed samples from across Southern NSW for herbicide resistance testing – free of charge to farmers.
Five samples are being sought (from different farms) across each of the following areas of the Riverina - NE (Narrandera, Griffith, West Wyalong), NW (Grenfell, Cowra, Harden, Cootamundra), SE (Holbrook, Culcairn, Lockhart) Central (Temora, Junee, Wagga).

What do you need to do to participate?

• Collect 2L of radish seed pods (from colour change onwards)
• Store in paper bag so they don’t sweat
• Record grower, paddock and herbicide history details.
• Contact Bayer’s Gus MacLennan for collection of seed.

This testing service is normally valued $380 per test, with results to be reported in 2017, while individual grower results and details to be kept confidential.
For further enquiries or to participate in the collection and survey please contact Lyndal Turner at FarmLink via or call (02) 6980 1333

Apr 27

Preparing for planting 2016

Posted by Cindy Cassidy at Wednesday, April 27, 2016

Rain forecast for this weekend means Riverina farmers are in the middle of preparing for, and sowing, the 2016 winter crop, an integral part of Australia’s agricultural output. Riverina farmers produce $2.1 billion worth of total agricultural output annually (ABARES) with grain production alone worth $795 million annually.
As a part of the preparation for this year’s crop, farmers have been using stubble burning as an important tool in the management of their farming systems. But why do farmers burn?
There are lots of reasons why farmers burn crop residue, but the overriding issue is that this stubble residue will adversely affect their cropping program, which can be compromised if the stubble -
• causes blockages to seeding equipment
• causes uneven crop emergence
• perpetuates crop diseases
• provides habitat for crop pests
• affects the efficacy of weed control
• affects the uptake of nutrients by the new crop
Farmers retain their stubble for as long as possible to provide grazing for sheep, to reduce erosion risk and to retain moisture.
Southern NSW produces some of the highest crop yields and best quality grain in Australia. Average wheat yields of 3-4 tonnes/ha are common, and could be double that in a good year. A direct result of that is that there is large amounts of stubble to deal with before the next crop can be sown. Typically stubble residue can be 1.5 x the grain yield. Research has shown that if the amount of stubble exceeds 3 tonne/ha then many seeders will have difficulties in sowing crops evenly and there will be blockages as the stubble tends to clump up. Getting crops sown to emerge within the correct time period for each variety is so important for the end result. Agronomists spend a lot of time planning crop rotations with farmers and selecting varieties suitable for each paddock to avoid frost and heat stress in critical times in spring, and this depends on the sowing operation going smoothly.
Many crop diseases and pests are harboured in the old stubble residue, so depending on the crop rotation the stubble may need to be removed to prevent the problems. Fungal leaf diseases such as Yellow Leaf Spot in cereals and Blackleg in canola are carried over in stubble residue. Stubble burning reduces these risks in the paddock so that crop seedlings are not exposed to the disease at emergence. Pests such as earwigs, millipedes and slugs rely on stubble cover to improve their habitat in cropping paddocks and can damage emerging seedlings, especially fragile canola seedlings. Removing the stubble by burning can help prevent these from causing a problem.
Weed competition is the greatest threat to crop productivity worldwide, so early control is essential for ensuring that crop yields are not compromised, and the emerging crop can become competitive itself. Stubble can interfere with efficient application of herbicides. Soil active pre-emergent herbicides will not be effective if stubble cover absorbs the spray, preventing even application. Post emergent weed control may also be compromised if standing stubble is shading seedling weeds so that spray droplets do not reach the target so burning stubble before herbicide application will give better results.
The technique of windrow burning as a way of destroying resistant weed seeds is also becoming an important part of the integrated weed management package. Instead of spreading harvested weeds seeds across the paddock, stubble residues are simply dropped via a shute at the back of the header so they can be burnt in late summer or early autumn in a hot burn that destroys all the weed seeds. This allows the majority of the stubble to be conserved, but herbicide resistant weed seeds are destroyed.
Stubble residues can also affect the uptake of nutrients to crops in some circumstances. Cereal stubble from high yielding crops can have a carbon : nitrogen ratio of 80 : 1. When this residue is incorporated into soil it will provide a feedstock for soil microbes. Carbon from crop residues is the primary driver of soil microbial activity and this in turn leads to the release of plant nutrients. The problem here is that the microbes (bacteria and fungi) need other nutrients, particularly nitrogen to digest this carbon. Nitrogen is stripped from soil reserves to do this, hence there will be a short term tie-up of nutrients that are not available to the emerging crop. Farmers have the choice of adding more nutrient for the crop, having the stubble residue in contact with soil for a longer fallow period, or removing the stubble by burning to avoid these nutrient problems. Local research showed that grazing stubbles over summer helped to avoid this nutrient tie-up and redistribute the nutrients across the paddock. Care needs to be taken to not over graze the stubble and increase the risk of soil erosion by wind and water.
Farmers do their best to avoid any impact of smoke on nearby communities by observing some basic principles when conducting stubble burning, including -
• checking with the Bureau of Meteorology and local Rural Fire Authorities when weather conditions will be suitable for burning
• avoiding calm weather conditions that are associated with temperature inversions where smoke will hang in the air for long periods and can drift into local towns.
• burning stubble in the heat of the day with a good cross breeze to give a quick, hot burn.
• awareness of when winds will take smoke into neighbouring towns.
Burning stubble can be done at various strategic times for many reasons, but there is a need to be aware of the “big picture” how it fits into the farming system and how it can be done to minimise the effects on the community.
FarmLink is continuing its work in the GRDC Stubble Initiative to ensure farmers have the support of their local communities thanks to improved stewardship of stubble burning and ongoing sustainable farm management practices.

Aug 26

Pacific Seeds Releases 2014 Hyola Hybrid Canola Techniques

Posted by Cindy Cassidy at Monday, August 26, 2013

The latest Pacific Seeds Hyola® Hybrid Canola Technotes with information on performance results,
product agronomic features and herbicide efficacy research relating to RT®, RR, TT and CL herbicide technology has been released.  Click on the links below to view documents.

Hyola RT Technology

Hyola RR Techonology

Hyola Clearfield Technology

Hyola TT Technology

Hyola Hybrid Graze n Grain

May 28

Microwaves to deliver chemical-free weed control

Posted by Cindy Cassidy at Tuesday, May 28, 2013

The technology that heats the common kitchen microwave oven has been adapted to deliver a chemical-free solution to Australia’s weed problems.

Dr Graham Brodie, of the University of Melbourne, has developed a fully operational prototype machine that can successfully focus microwave energy at ground level, killing weeds within seconds.

“Herbicide resistance and environmental concerns already limit the chemical options available for weed management,” Dr Brodie said.

“In looking for alternative weed treatments, we have found that microwave treatment is immediate, chemical-free and leaves no residue at the treatment site.”

Weeds are one of the major threats to Australia’s primary production and to the natural environment. It has been estimated that weeds cost Australian agriculture more than $4 billion dollars each year, including control costs and lost production.

Dr Brodie’s research during 2011-12 was conducted as part of the Australian Government’s National Weeds Research and Productivity Program, administered by the Rural Industries Research and Development Corporation (RIRDC).

The Commonwealth provided $12.4 million to RIRDC to support more than 50 research projects, with the program ending on 30 June 2012. The funding covered the first two years of a five-year National Weeds and Productivity Research Program R&D Plan for 2010-2015.

The RIRDC Weeds Program invested in projects aimed at improving knowledge and understanding of weeds, as well as delivering new treatments, with 11 research projects dealing directly with herbicide resistance issues.

Interest in the effect of microwaves on plant health dates back to the 1920s, but it was not until recently that studies shifted away from attempting to treat seeds in the soil and instead targeting plant seedlings.

The concentration of microwave energy collapses the structures within the weeds that carry water through their stems. Depending on the amount of energy applied, irreversible wilting and subsequent death occurs within just seconds of the microwave exposure.

Dr Brodie’s research initially tested a 600-watt kitchen microwave, before developing the 8-kilowatt field unit that has been tested in the paddocks at the university’s Dookie campus.

A series of four microwave horn antennae, each just 11cm wide and transmitting 2kW of microwave energy, were fitted to a trailer to focus their transmission solely onto the weeds in the inter-row space of agricultural field crops.

Dr Brodie said that in a broadscale agricultural operation numerous antennae could be mounted on a tractor trailer at spacings in line with whatever crop was being treated.

Treatment could take place regardless of the weather conditions, would successfully kill herbicide resistant species, and would not limit production schedules with withholding periods at the site once treatment is completed, he said.

“There is potential to develop an industrial 15kW unit which could operate in broadacre situations at near the speed of current chemical spray applicators, with each weed requiring less than a second of exposure to the microwave transmission,” Dr Brodie said.

“Microwave weed management has the potential to be applied throughout Australia to manage weeds not just in agricultural enterprises, but on public land, sporting facilities and in landscape gardening.

“A smaller 1-2kW unit could also be designed for use by householders if the market supported the concept.”

• The prototype microwave system is now operational and can be demonstrated to interested parties who may wish to use the technology in commercial systems. More information on the National Weeds Program is available at

May 24

The Rate Debate

Posted by Cindy Cassidy at Friday, May 24, 2013

Many a late night has been spent over a glass of red at weeds conferences around the world debating whether high or low herbicide rates lead to faster resistance evolution. All weed scientists have an opinion on this issue, some of which are held very tightly. To some extent, the debate is still raging because the answer is not straight forward. The answer is both. As you can imagine, both sides of the debate are claiming victory! 

What we do know is that low herbicide rates have been documented to lead to rapid resistance evolution to Hoegrass®, Roundup® and Sakura® in annual ryegrass. The problem is that we need to do the research for each weed and each herbicide, one at a time, to determine if this is a recurring theme, and if there are exceptions to the rule.  

In a world first, AHRI postdoctoral fellow Roberto Busi evolved resistance to the new herbicide Sakura® before it was even commercially released. Roberto found that ryegrass evolved resistance (8 fold) to Sakura® after just three generations of recurrent selection at low rates. A similar study by Dr Paul Neve at AHRI in 2005 found that ryegrass developed 55 fold resistance to Hoegrass® after three generations of recurrent selection at low rates. This tells us that weeds find it easier to evolve resistance to some herbicides more so than others, but the end result is still a resistant weed.

Given that we can’t put the rate debate to bed for all weeds and all herbicides yet, we should give the weeds the benefit of the doubt, and assume that low herbicide rates are bad news until proven otherwise. Guilty until proven innocent!

Dr Paul Neve was the first scientist to confirm resistance evolution in ryegrass to low doses of Hoegrass®. Paul started with 107 ryegrass seedlings to which he applied 10% of the label rate of Hoegrass®. He then took the survivors, allowed them to cross pollinate with each other and grew them out to seed. He then grew seedlings from this seed and sprayed them with 20% of the label rate of Hoegrass® and once again allowed the survivors to cross pollinate and set seed. For the third generation he sprayed the full label rate of Hoegrass®. At the end of this process, Paul had evolved ryegrass to have 55 fold resistance (that is 55 times the rate at which 50% of the population is controlled - LD50). The reason for this resistance evolution was later confirmed to be due to metabolic resistance caused by multiple gene mutations. Since this original experiment, Paul’s work has been repeated several times and has also been conducted in a field experiment. These consistent results confirm resistance evolution in ryegrass to low doses of Hoegrass®. 

Enter Dr Roberto Busi, winner of the Perth marathon and passionate Italian who has lived and breathed the effect of low herbicide dose on resistance evolution over the past seven years. Roberto used an approach similar to that of Paul Neve as described above, only this time he used the herbicides Sakura® and glyphosate. The result was that resistance evolved, but at a much lower level (only 1.7 to 1.9 fold resistance compared to 55 fold for Hoegrass®). However, when he started with ryegrass that had already developed resistance to Group A (ACCase), Group B (ALS) and Group D (trifluralin), and exposed it to three generations of low rates of Sakura®, the populations developed 8 fold resistance to Sakura®. The somewhat surprising result was that this ryegrass was also resistant to Boxer Gold®. This resistance was later confirmed to be due to a single gene mutation.

Table 1. Summary of low dose resistance evolution research in annual ryegrass. Hoegrass® active ingredient Diclofop methyl. Sakura® active ingredient pyroxasulfone. Boxer Gold® active ingredients prosulfocarb and metolachlor.


What about broadleaf weeds?

There has been limited work on broadleaf weeds in this area. However, the research that has been done shows similar results. Mike Ashworth is currently doing his PhD at AHRI on wild radish and has put low doses of glyphosate and 2,4-D to the test. The preliminary data of this research suggests that where he exposed wild radish to low doses of glyphosate he measured a small shift towards glyphosate resistance. Where he exposed wild radish to low doses of 2,4-D he saw a bigger shift and observed that wild radish were resistant to field rates of 2,4-D after just three generations of recurrent selection at low dose. 

Scientists may continue to argue whether low doses or high doses cause faster resistance evolution. What is clear is that there is now well documented evidence that low herbicide doses do select for resistance after just a few generations and there are differences between weeds and herbicides as to how fast this resistance evolves.

Source: Australian Herbicide Resistance Initiative (AHRI)

May 06

Weed Destructor integrated into harvester

Posted by Cindy Cassidy at Monday, May 06, 2013

The Harrington Seed Destructor (HSD) is on the verge of taking the step that most grain growers would like to see. The majority of Australian grain growers who have seen the HSD are very positive about the concept of destroying weed seeds as they exit the harvester. It seems crazy that we would spread the weed seeds back over the field (so we have something to spray next year!). However, many growers have commented that they are reluctant to tow such a machine behind their harvester.

Agricultural engineers from the University of South Australia in collaboration with AHRI, are taking the Harrington Seed Destructor to the next level. They have built the first prototype of a mill that is mounted within the rear of the harvester to destroy weed seeds as they exit in the chaff fraction. This technology is still in the prototype stage, and the first indications are very exciting.

This new version of the HSD is known as the Integrated Weed Destructor (IWD). It is a modification of the original HSD invented by Ray Harrington, grain grower from Darkan, Western Australia. The HSD has proven efficacy, consistently destroying greater than 95% of the seeds of a range of weed species that enter the mill (see paper below).

The IWD mill is a slightly different design to that which features in the HSD. As such, the IWD will be put through its paces this year by Dr. Michael Walsh (AHRI) to determine the kill rate of a range of weed species. Initial testing and modelling suggests that the IWD mill should be as effective as the HSD mill at destroying weed seeds.

The video below shows two IWD mills mounted to a class nine harvester (hydraulically driven) operating at approximately class eight capacity (up to 40 t wheat harvested /hour). Chaff from the main sieve is directed into the mills via a simple chute. It requires approximately 80 to 100hp to drive the mills, which is why the harvester operates below maximum capacity.

This is clearly an exciting development for the future of weed seed crushing, however keep in mind that the HSD is a proven performer and is currently commercially available. De Bruin engineering (see link below), the manufacturers of the HSD, will continue to build a small number of tow-behind HSD’s to meet current market demand whilst testing and development of the IWD occurs over the next few years.

It is widely acknowledged by many in the agricultural industry that weed seed destruction at harvest is necessary as a key non-herbicide weed control tool to manage herbicide resistant weeds. GRDC, AHRI, University of South Australia and De Bruin engineering are all committed to delivering this world leading technology to Australian grain growers. There are clearly opportunities to develop this technology in other countries in the future.

Follow the links below for further information: