Geek Out on Science 

14 Year's Research Summary

01

Stop the spread and manage the patches

02

Cut the costly sprays and save your crops

03

Delay herbicide resistance and keep costs down

04

Boost your yields by playing the numbers game

WE WROTE THE BOOK ON MECHANICAL WEED CONTROL

Putting Australia's highest performing mill to the test


South Australian Grain Industry Trust (SAGIT) Benchmark Report
2022/2024 Key Takeaways

Independently Observed by Kondinin Group

Test for the real world or not at all

Mill efficacy on native annual ryegrass seed present in source chaff. Chaff was sourced from Balaklava, South Australia and contained a population of small, naturally occuring annual ryegrass (Lolium rigidum) seeds. 

Previous studies have demonstrated control rates of up to 99%. These tests typically used larger, commercially-sourced seeds, suggesting that smaller seeds, having endured the selective pressures of the season, are harder to kill, esspecially Lolium rigidum.

Unless your mill has been pitted against real Australian ryegrass, you can’t be sure it will be up to the task. 


Our mills outperformed others, across the board

Seed Terminator was able to maintain above 90% control at increasing infeed rates at 100% RPM. At reduced mill speeds, we still maintained a higher level on control that other mills. Seed Terminator was also least affected by the cushioning effect of more chaff.



More energy means more kill

Energy consumed in chaff processing was found to be directly correlated with ryegrass control. Mills inputing more energy achieved higher levels of control – Seed Terminators input more energy overall.



Wear reduces kill rate

All worn mills trended lower for control of annual ryegrass. Even with the highest level of wear, worn Seed Terminator mills maintained the highest level of control. 


Not all weeds are made equal

Mill efficacy against wild radish was excellent for all mill types, averaging 99% across all tests. Seed Terminator demonstrated the highest control rates against small-flowered mallow.

Knowing what you are targeting can be to your advantage when choosing the best mill type for your harvest.

Australian annual ryegrass is Lolium Rigidum. Results collected from any other variant don’t hold up in the field.


Dr Nick Berry provides commentary on the South Australian Grains Industry Trust Mill Report

"After 14 years of working out how to kill the prolific Australian weed, annual ryegrass onboard a harvester, table 1 in the recent study still hit me right between the eyes."

  • At modest throughput, we see the lowest level of control I've seen in the iHSD mill (from my PhD), Seed Terminator Standard, and High Capacity machines.
  • For 15 years, world-class research in Australia has focused on testing with seed sourced from pasture seed growers for its supply and consistent viability, but this test's weed seeds proved exceptionally tough to kill due to their small size.


Start with the customer – find out what they want and give it to them.

Start with the customer – find out what they want and give it to them.

Start with the customer – find out what they want and give it to them.

Start with the customer – find out what they want and give it to them.

February 2024

SAGIT Mill Testing TL;DR

What insights can we learn from the SAGIT Benchmark Mill Testing?

Read more​

Pilot Mill  Benchmark Testing 2021

Original pilot test results from 2021 with a limited testing program, benchmarking all three mill manufacturers.

Read more

Kondinin Research Report 2020

The war against weeds continues with learnings from 20 farmers across Australia. 

Read report

Kondinin Research Report 2018

Early learnings around mill technology and harvest weed seed control. 

Read report

Original 2017 SAGIT Testing

Optimisation of Seed Terminator settings in the South Australian Context from Sam Trengove, Trengove Consulting. 

See Results

Why do combines spread weeds?



Let's unpack what is going on inside the combine harvester

1 Crop Collection
Most weed species are annuals, and are mature with seeds the same as the crop we are harvesting. This means when the combine harvester begins its operation with the header front, either cutting and collecting the standing crop or picking up a windrow its harvesting the crop and weeds.

4 Separator 
The separator removes the remaining grain from the straw material and transfers the grain and weed seeds to the cleaning shoe.

3 Threshing
At the heart of the combine harvester's operation is the threshing process. The crop and weed material is forced between the threshing cylinder and concave where impact, compression and shear forces detach the grain from the heads. 

Small material which includes 70-90% of the threshed grain falls through the concave grate onto the cleaning shoe. The remaining larger material, including mostly straw moves to the separator.

Concave settings are important to avoid over-threshing small sections of straw into the chaff stream.

2 Feeder House
Once the crop is collected, it is transported to the thresher via the feeder house. This component acts as a bridge that efficiently moves the cut crop from the header front to the thresher for the next stage of processing.

First, lets understanding Fan Speed and Terminal Velocity in Combine Harvesters

When you're harvesting different types of crops with a combine harvester, adjusting the fan speed in your machine is crucial. But why is this adjustment necessary? It all boils down to a concept called terminal velocity—the maximum speed at which particles, like grains, fall through the air.

What is Terminal Velocity?

  • Canola: Approximately 3 meters per second
  • Wheat: Ranges between 7 to 9 meters per second
  • Ryegrass: Similar to canola, about 3 meters per second

This means, for each type of grain, you need to set the airflow through the harvester's sieves to match this speed. Ideally, the airflow should be just enough to lift the chaff (the husks and other debris) but allow the grain to fall through the sieves. If the airflow matches or exceeds the terminal velocity of the grain, you risk blowing the grain right out of the harvester, losing valuable yield.


The Role of the Cleaning Shoe 

The cleaning shoe of a combine harvester uses a combination of aerodynamic forces and mechanical sieving to separate the grain from other materials (often referred to as MOG, or Material Other than Grain). Here’s how it works:

  • Large Material: Separated mechanically by oscillating sieves.
  • Low Terminal Velocity Material: Such as chaff and weed seeds, pneumatically separated due to its lower terminal velocity.
  • Tailings: Material that passes through the first sieve but is too large for the second is sent back for further threshing.
  • Clean grain: has a higher terminal velocity, it falls to the bottom and is then funnelled into the grain tank using a system of elevators and augers. This tank stores the grain during the harvest. Once full, the grain is easily unloaded through another auger.

Adjusting for Conditions The terminal velocity of wheat and other grains can vary significantly based on moisture content, grain variety, and other conditions. That means the harvester settings need to be tailored specifically to the conditions and the crop variety to ensure optimal efficiency and minimal loss.

By understanding and controlling the airflow and its relationship with terminal velocity, you can significantly enhance the efficiency of your combine harvester and capture of pesky weed seeds.



Where do weed seeds end up in a combine harvester?

The short answer is that it depends.

Depending on the crop type around 3% of weed seeds can end up in grain tank. We can maximise the percentage that ends up in the chaff stream and minimise the % in straw by managing rotor loss. Loss testing 

Where does the tailings return system fit in?

Nick shares the story of harvesting in Western Australia in one of the newer John Deere S-series at the time with the Active Tailings System (read camera of the tailings return). They went through some low lying country, that had a huge population of ryegrass, the camera showed the tailings return load up with ryegrass and it took hundreds and hundreds of meters for them to finally process through, he jokes, there was a Terminator on the back, so it was no worries!

A study in the fate of weed seeds from 2014

John Broster from CSU and Michael Walsh from Sydney University conducted studies to understand how many weed seeds were captured in the chaff fraction by modern harvesters. 10,000 coloured ryegrass seeds were fed into the front of the harvester and then painstakingly, it was measured where they ended up. Their initial 2014 trials with five different harvesters in NSW revealed that a significant number 47% of weed seeds were mistakenly being discarded with the straw fraction, posing challenges for effective Harvest Weed Seed Control (HWSC). 

However, subsequent trials in 2015 with a specially equipped harvester demonstrated improved capture of weed seeds in the chaff stream 97%, indicating that harvester setup is crucial. These studies also highlighted that harvest speed did not significantly impact the distribution of weed seeds, though it did affect grain losses.

Full Separation of Chaff & Straw Fractions 

In combine harvesters, properly segregating chaff and straw is vital, particularly when using a chaff mill. If straw enters the mill, it can lead to reduced capacity, clogging, or excessive wear on the machinery. To avoid these issues, Seed Terminator retrofits harvesters with custom designed baffle plates. Positioned behind the beater, these modifications maintain separate straw stream ensuring the material doesn't enter the mill, guiding it towards the chopper at the rear of the harvester.

  • Case IH combines are updated with enhanced baffles to better manage straw flow.
  • John Deere S Series Seed Terminator have developed the Straw Streamliner to improve the separation of chaff and straw without hindering airflow or blocking the sieves.
  • John Deere X Series:  The original shaker tray is replaced with a custom engineered replacement to further optimise separation.
  • CLAAS: Known for its efficient separation, CLAAS combines naturally segregate straw and chaff, making them well-suited for harvest weed seed control without additional modifications.
  • New Holland: In models like the CR combines, there is a significant gap (1200mm) between the beater and the chopper, which can be problematic in tough conditions like wet lentil vines or brittle straw. To address this, a Dynamic Straw Streamliner (DSS) has been developed by Seed Terminator, which extends across the entire gap, ensuring all straw is directed to the chopper and maintaining clear separation from the chaff.

Straw Residue

The straw residue separated from the plant is cut into smaller pieces by a straw chopper. This step is crucial for preventing blockages in future planting, especially when using no-till farming methods. This residue is spread across the paddock, preferably full width as the residue is a valuable source of nutrients (P,K,N) for the next crop.

Single Belt Design

Less belts, more drive.
Moving to a single serpentine belt to drive both mills, means superior drive performance 


Chopper Home
The Seed Terminator SmoothFEED 2 allows the chopper to operate in
the factory position for improved integration.
Allowing the chopper to resume its factory position improves the straw material flow, for smoother operation.

Managing weed seed spread with combine harvesters 

Combine harvesters play a crucial role not only in harvesting crops but also in managing the spread of weeds. Research shows that combine harvesters are responsible for a significant dispersal of weed seeds across paddocks, capturing weed plants and seeds that are above the cutting height of the header.

Key Findings:

  • A large proportion of weed seeds, often more than 50%, remain at a height that allows them to be collected by the combine harvester at harvest time.
  • Depending on the species, seed retention percentages can vary significantly, influencing how and where these seeds are distributed post-harvest.

What Happens Inside the Harvester:

  • Weed seeds that end up on the cleaning shoe with grain and chaff can either be collected in the grain tank or expelled with the chaff, depending on their terminal velocity relative to the airflow through the harvester's sieves.
  • Many weed seeds have a lower terminal velocity than the grains being harvested, which means they are likely to be expelled with the chaff, although this can vary by species.
  • Processing all the residues (chaff and straw) exiting a combine harvester with a mill would require an inordinate amount of power.  

Opportunities for Control:

  • By intercepting and managing the chaff and straw expelled by the harvester, it's possible to significantly reduce the spread of weed seeds. This can be an effective strategy to control the weed seedbank without relying solely on herbicides.

The effective management of weed seeds during harvesting can have a substantial impact on the weed populations in subsequent crop cycles, highlighting the importance of strategic harvester settings and post-harvest residue management.

Managing weed seed spread with combine harvesters 

Combine harvesters play a crucial role not only in harvesting crops but also in managing the spread of weeds. Research shows that combine harvesters are responsible for a significant dispersal of weed seeds across paddocks, capturing weed plants and seeds that are above the cutting height of the header.

Key Findings:

  • A large proportion of weed seeds, often more than 50%, remain at a height that allows them to be collected by the combine harvester at harvest time.
  • Depending on the species, seed retention percentages can vary significantly, influencing how and where these seeds are distributed post-harvest.

What Happens Inside the Harvester:

  • Weed seeds that end up on the cleaning shoe with grain and chaff can either be collected in the grain tank or expelled with the chaff, depending on their terminal velocity relative to the airflow through the harvester's sieves.
  • Many weed seeds have a lower terminal velocity than the grains being harvested, which means they are likely to be expelled with the chaff, although this can vary by species.
  • Processing all the residues (chaff and straw) exiting a combine harvester with a mill would require an inordinate amount of power.  

Opportunities for Control:

  • By intercepting and managing the chaff and straw expelled by the harvester, it's possible to significantly reduce the spread of weed seeds. This can be an effective strategy to control the weed seedbank without relying solely on herbicides.

The effective management of weed seeds during harvesting can have a substantial impact on the weed populations in subsequent crop cycles, highlighting the importance of strategic harvester settings and post-harvest residue management.

Managing weed seed spread with combine harvesters 

Combine harvesters play a crucial role not only in harvesting crops but also in managing the spread of weeds. Research shows that combine harvesters are responsible for a significant dispersal of weed seeds across paddocks, capturing weed plants and seeds that are above the cutting height of the header.

Key Findings:

  • A large proportion of weed seeds, often more than 50%, remain at a height that allows them to be collected by the combine harvester at harvest time.
  • Depending on the species, seed retention percentages can vary significantly, influencing how and where these seeds are distributed post-harvest.

What Happens Inside the Harvester:

  • Weed seeds that end up on the cleaning shoe with grain and chaff can either be collected in the grain tank or expelled with the chaff, depending on their terminal velocity relative to the airflow through the harvester's sieves.
  • Many weed seeds have a lower terminal velocity than the grains being harvested, which means they are likely to be expelled with the chaff, although this can vary by species.
  • Processing all the residues (chaff and straw) exiting a combine harvester with a mill would require an inordinate amount of power.  

Opportunities for Control:

  • By intercepting and managing the chaff and straw expelled by the harvester, it's possible to significantly reduce the spread of weed seeds. This can be an effective strategy to control the weed seedbank without relying solely on herbicides.

The effective management of weed seeds during harvesting can have a substantial impact on the weed populations in subsequent crop cycles, highlighting the importance of strategic harvester settings and post-harvest residue management.

Managing weed seed spread with combine harvesters 

Combine harvesters play a crucial role not only in harvesting crops but also in managing the spread of weeds. Research shows that combine harvesters are responsible for a significant dispersal of weed seeds across paddocks, capturing weed plants and seeds that are above the cutting height of the header.

Key Findings:

  • A large proportion of weed seeds, often more than 50%, remain at a height that allows them to be collected by the combine harvester at harvest time.
  • Depending on the species, seed retention percentages can vary significantly, influencing how and where these seeds are distributed post-harvest.

What Happens Inside the Harvester:

  • Weed seeds that end up on the cleaning shoe with grain and chaff can either be collected in the grain tank or expelled with the chaff, depending on their terminal velocity relative to the airflow through the harvester's sieves.
  • Many weed seeds have a lower terminal velocity than the grains being harvested, which means they are likely to be expelled with the chaff, although this can vary by species.
  • Processing all the residues (chaff and straw) exiting a combine harvester with a mill would require an inordinate amount of power.  

Opportunities for Control:

  • By intercepting and managing the chaff and straw expelled by the harvester, it's possible to significantly reduce the spread of weed seeds. This can be an effective strategy to control the weed seedbank without relying solely on herbicides.

The effective management of weed seeds during harvesting can have a substantial impact on the weed populations in subsequent crop cycles, highlighting the importance of strategic harvester settings and post-harvest residue management.

Managing weed seed spread with combine harvesters 

Combine harvesters play a crucial role not only in harvesting crops but also in managing the spread of weeds. Research shows that combine harvesters are responsible for a significant dispersal of weed seeds across paddocks, capturing weed plants and seeds that are above the cutting height of the header.

Key Findings:

  • A large proportion of weed seeds, often more than 50%, remain at a height that allows them to be collected by the combine harvester at harvest time.
  • Depending on the species, seed retention percentages can vary significantly, influencing how and where these seeds are distributed post-harvest.

What Happens Inside the Harvester:

  • Weed seeds that end up on the cleaning shoe with grain and chaff can either be collected in the grain tank or expelled with the chaff, depending on their terminal velocity relative to the airflow through the harvester's sieves.
  • Many weed seeds have a lower terminal velocity than the grains being harvested, which means they are likely to be expelled with the chaff, although this can vary by species.
  • Processing all the residues (chaff and straw) exiting a combine harvester with a mill would require an inordinate amount of power.  

Opportunities for Control:

  • By intercepting and managing the chaff and straw expelled by the harvester, it's possible to significantly reduce the spread of weed seeds. This can be an effective strategy to control the weed seedbank without relying solely on herbicides.

The effective management of weed seeds during harvesting can have a substantial impact on the weed populations in subsequent crop cycles, highlighting the importance of strategic harvester settings and post-harvest residue management.

Start with the customer – find out what they want and give it to them.

Material Function


What factors affect the likelihood of a weed seed being terminated? 

Each species will have a different emergence response when seeds are subject impact loads. This response is related to the seed’s strength, fracture toughness, mass, terminal velocity and natural defences. Therefore, each target weed species will require a different amount of impact energy to provide effective control.

In Australian cropping systems our main focus for weed kill has been Annual Ryegrass (lolium rigidium) due to its prevalence as a weed species and also as it is very difficult to mechanically kill. This is due to its high fibre to starch ratio (meaning it is very tough) and because it is very light (hitting it doesn’t provide a lot of energy for seed damage). 

Interestingly, some weeds like Wild Radish are incredibly easy to kill with a mill, recent benchmark testing indicates 99% termination across a wide range variables. This is due to its high oil content; it requires less energy to critically damage the seed. 

Seed retention above 15 cm harvest height over the first 4 weeks of harvest for the major crop weeds of Western Australian wheat crops.

M Walsh, S Powles (2012) Harvest weed seed control. GRDC Update Papers 12 April 2012, http://www. grdc.com.au/Research-and-Development/GRDC-Update-Papers/2012/04/Harvest-weed-seed-control

Studies conducted by Michael Walsh from the University of Sydney and John Broster from Charles Sturt University have highlighted that stronger crop competition can force weeds like ryegrass to grow taller, seeking light, and thus setting seeds higher within the crop canopy. This positioning increases the likelihood of capturing these seeds during the HWSC process.

In a study examining the impact of crop density on weed seed retention, significant differences were observed across various weed species at two different densities of wheat plants. At a lower density of 60 plants per square meter, seed retention above 40 cm at crop maturity was recorded at 50% for annual ryegrass, 57% for wild oats, 83% for wild radish, and only 5% for brome grass. However, when the wheat density was increased to 400 plants per square meter, seed retention improved dramatically: 93% for annual ryegrass, 70% for wild oats, 98% for wild radish, and 70% for brome grass. Additionally, this increase in plant density led to reductions in total seed production ranging from 74% to 91% for these weed species, indicating a strong suppressive effect of higher crop density on weed growth and seed output. 

When using Impact alone 
Annual ryegrass seed devitalisation reduced with increasing moisture content. A linear regression showed that every 1% increase in moisture content reduced seed devitalisation by approximately 2.2%. Using single-sided for mechanical control of weed seeds will require increased impact energy (higher impact speeds and/or number of impacts) at higher moisture contents.


4 Modes of Action: Crush, Shear, Grind AND Impact

The Multistage Hammer Mill AeroImpact technology which is the heart of the Seed Terminator Origin and Pro platforms outperforms in tough conditions with high moisture, smaller seed size or drops in RPM due to its four modes of action. 

Check out the SAGIT Report

In 2022 SAGIT funded Trengove Consulting to benchmark multiple mills on the see the affect of really small annual ryegrass (2.1mg) seed on kill testing. 

There is further research on real in paddock seed size coming in 2024. Early indications suggest viable seeds could range from 1.1mg per seed to 3.1, with the majority at 2.6mg. 

Potential Evolution of Resistance

Like all weed control strategies, the long-term viability of Harvest Weed Seed Control (HWSC) could be compromised by the evolution of resistance mechanisms in weeds (Powles and Yu 2010). In terms of HWSC, 'resistance' could involve adaptations that help weed seeds escape capture. For instance, certain weeds might develop traits such as early seed shattering—where seeds fall before harvest—or a growth form that is more prostrate, keeping seeds below the height reached by harvesting equipment. These adaptations could enable weeds to bypass the HWSC systems. 

Although research has shown variations in seed retention at maturity, which could indicate potential adaptation, no concrete evidence of such adaptation has been observed in annual ryegrass, a major target of HWSC in Australia for over two decades (Walsh et al. 2018a).


Single Belt Design

Less belts, more drive.
Moving to a single serpentine belt to drive both mills, means superior drive performance 


Chopper Home
The Seed Terminator SmoothFEED 2 allows the chopper to operate in
the factory position for improved integration.
Allowing the chopper to resume its factory position improves the straw material flow, for smoother operation.

Cleaning Shoe Performance is Unaffected.

Seed Terminator causes no restrictions of airflow within the harvester cleaning shoe = confidence in the accuracy of grain loss checks = confidence in your harvester setup to minimise grain loss.

Pitot tube, hot wire anemometer to measure the air flow. Torque transducer to measure torque. Dustpan and broom to measure kill! >

Start with the customer – find out what they want and give it to them.

An overnight success story, a decade and counting.

Insight in how a young farm kid from Kangaroo Island, South Australia became the world expert in stopping 80% of the worlds weeds being spread from the back of combine harvesters. Globally. 

​Let’s reel back a bit. Quite a bit, actually, to the 1960s. Back then, the herbicides available weren’t up to much, so farmers had to rely on tillage – churning up the soil prior to planting - to control weeds.  They knew it wasn’t ideal. 

Then along came a significant change. “All of a sudden we started to get some really effective chemicals come out, like glyphosate, which facilitated a whole change in agricultural practice. We moved away from tillage altogether, particularly in Australia.”

Still the world’s most used herbicide, glyphosate saw yields go up, and a lot of area that wasn’t suitable for cropping suddenly became viable. Globally, glyphosate use has risen almost 15-fold since “Roundup Ready,” genetically engineered glyphosate-tolerant crops were introduced in 1996. 






  • 2011: Enhancements in Harrington Seed Destructor's Chaff Transfer 'Improving the Chaff Transfer System of the Harrington Seed Destructor (HSD)' This study looked at the role of airflow and evaluated Pneumatic Conveying System over the existing cross augers and slinger fans used by chaff carts at the time to improve the chaff transfer system of the Harrington Seed Destructor. 
  • 2012: Power Use in the Harrington Seed Destructor 'Relating the power used by the Harrington Seed Destructor to chaff throughput' Previously limited to use with Class 6 harvesters, Nick monitored the power required over varied chaff and grain rates to determine the No Load Power & Chaff-to-grain ratios (to scale to other harvesters) with the HSD Version II on a JD 9650.
  • 2013: Difference in terminal velocity of wheat chaff particles and Annual Ryegrass (Lolium rigidum) 'Opportunities to reduce the chaff processing requirements of a harvester weed seed destructor' The energy requirements to terminate weed seeds was immense. Nick explored reducing the amount of chaff being processed as an avenue to reduce that requirement. Aerodynamic removal could theoretically eliminate 22% of chaff while retaining 95% of Ryegrass seeds. Sieving alone could collect 90% of Ryegrass seeds, removing up to 30% of chaff.



'A multistage hammer mill and a residue processing system incorporating same'

An advantage of hammer mills is that in addition to impact, they induce crushing, shear and attrition forces that make them particularly useful for size reduction of fibrous materials. Another advantage of hammer mills is that they often have flexible impact elements that are replaceable and can handle some foreign objects without damage




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Terminator Agro Translates
'A PhD on Smashing Weeds'

For Hardcore Enthusiasts
Read Nick's PhD > 

Take a look at Target Weed Species