Updated: February 2025.
Tecfarm WeedHOG Seed Mills have now operated for up to five harvests. Professionally conducted static bed tests followed by infield data collection have been documented over hundreds of hours. Further valuable experience and confidence has been gained. Some small engineering issues addressed. As with any machinery that is performing a very difficult job, ongoing improvements will be possible.
Some observations from ’25 harvest:
New Holland CR harvesters operating in cereals and possibly canola, discharge long straw from the beater. To avoid ‘bridging’ at the mill entry and unnecessary power loss it’s essential to fit a short conveyor (NH PSD) or similar, to transport this material over the mill inlet and into the chopper. For JD and Case it’s not required.
WeedHOG continues to handle green sappy material well, mostly due to its inherent “open flow” design.
Correct setup of entry trays/baffles is important to allow good flow of all crop types. This is especially so for green stemmed canola and similar.
To retain maximum weed control, rotor bars can be reversed on the shafts to achieve a new edge. Most owners have rotated impact bars at least once. Some owners will replace bars this season after three harvests. While it has not been tested at this time, we would advise changing the bars at regular periods to maintain a sharp milling face.
WeedHOG’s low power requirement means a very simple drive design is possible.
Tecfarm Smallbore has now successfully completed a full season of commercial use in the Southern Yorke Peninsula of South Australia. It’s a mill that is suited to the smaller harvesters. The low power requirement made it an achievable and “game changing” goal.
The WeedHOG story:
Some years ago, alongside the successful Tecfarm chaff cart the design team undertook to develop a simple and reliable Harvest Weed Seed Control Mill that would be a cost effective option for many farms. After much research and development the machine now known as WeedHOG emerged. It stands alone in the field of seed mill engineering with its totally unique and innovative mode of action. WeedHOG’s rotors force an exchange of seeds across a gap between two conjoined circular housings. This results a high speed impact of seeds with the opposing rotor bars. WeedHOGs’ engineering is simple, but there are very complex interactions of air and material. Gaining some understanding of the air flows and material physics involved has been a challenge.
Development:
After initial proof of concept testing over several years, successful field trials were carried out at Bruce Rock WA during the 2018 harvest using a ‘Two Rotor’ unit mounted on a Case 9120 harvester. While very encouraging, it was felt that a larger capacity mill may better suit the larger class 8-9 harvesters. So during 2019 there was a period of intense work to design a larger mill. The prototype trialled during 2018 harvest was studied at length, refined and given higher capacity. This was achieved by doubling the effective area within the mill, (the ‘Quad Rotor’ design) and adding additional impact points on each rotor to give greater efficiency. The original Two Rotor design with modified rotors and a simplified drive system is now been developed as the WeedHOG Smallbore mill suited for up to Class 7.
Several years of observation and multiple testing show a big reduction in Annual Ryegrass (lolium rigidum) germination, the main winter crop weed in Southern Australia and most difficult to kill as it is light and small.
Testing methods include sowing measured amounts of collected chaff/seeds in replicated 4m2 field plots for grow out, small trays and petri dishes. These methods have proven reliable and show high direct kill out of the mill.
From our extensive trial work in practical field conditions, initial seed kill percentage while high, can vary due to many factors. Research by Tecfarm and others both in Australia and overseas as far back as 1958, indicate that complete destruction is not necessary to render seeds unviable after exposure in a field environment. Even minor damage is all that is needed. Observations by Tecfarm personnel verified this phenomenon quite early in testing. On revisiting field plots several months after harvest and counting emergence of Ryegrass, results are remarkable with around 95-98% reduction compared to unmilled control plots. This phenomenon has implications for how much energy is required for longer term weed control using a mill. As well as Wimmera rye grass, larger weed seeds and volunteer crop seeds have practically a total kill. The low power requirement of the WeedHOG means almost all harvesters are capable of sufficient power and likely not to require aftermarket remapping of engines.
These observations show that as well as completely destroying a large percentage, the mill damages a high proportion of the remaining seeds while chaff tends to be left somewhat intact with a low amount of very fine material. This may be a reason for the units’ observed low power requirement. The Quad Rotor Mill indicates power use at around 40HP (30Kw). Energy is not wasted in making a high proportion of dusty, fine particles.
A major reason for the persistence of annual ryegrass in cropland is its tendency for high levels of dormant seed preventing full germination in any one generation. After passing through the mill the small number of seeds escaping a total kill are observed to have almost all suffered damage and if not subject to infield degradation, appear to have their natural high level of dormancy broken, a trait that is useful to allow spraying out early in the cropping season. Attack by soil borne fungi, microbial activity etc. is also something that seems to happen to damaged seed that has had its’ protective coat compromised. As mentioned above this environmental aspect of the effect of seed mills on seed viability has been seen here at Tecfarm and by other researchers.
eg.This “environmental effect” has also been observed by Shergill et al 2019 in their testing of the Harrington Seed Destructor in the USA. It has also been studied previously in extreme detail for the weed seed “cheat” by Hauhouot (1991 and 1999) and Gossen 1998) who found that even small nicks and cuts caused predation and death by soil microbes. Davis (2016), who has also worked on weed seed survival strategies for many years, observed that many of our worst agricultural weeds have seeds with limited chemical/physical protection in their seed coats. “Only small amounts of damage need be applied to each seed to ensure the rapid demise of the most recalcitrant species in the weed seedbank“ and “in practical terms this means that harvester need not turn seeds into “fine homogenates” in order to be effective”
It means that the need for total destruction of seed is unnecessary for good control. This has very practical implications for mill design going forward. Attack by soil fauna and pathogens after even minimal damage to seed coats is very beneficial in giving ‘free’ control.
WeedHOG features:
- Lower capital cost
- Minimal power requirement
- Good efficacy on common weed species and volunteer crop seeds
- Open rotor and housing design reduces green material build up and plugging
- Unique rotor design eliminates expensive specialised balancing
- Easy maintenance and low cost rotor bar replacement
- Impact bars are reversible to maximise service life
- Bar sets can be added or removed to suit field/crop conditions and power availability
- Controllable inflow to suit crop/weed conditions
- Integral Bolt Trap
The future: February 2025. With engineering and efficacy testing over five Australian harvests and having carried the project to this point with limited private resources, Tecfarm is seeking a company experienced in harvest equipment to manufacture and market these innovative units by either the sale or license of the design IP.
Contact info: Tom Lewis: 0428 611 309 tom@tecfarm.com.au
Tecfarm Seed Mills are protected under one or more of the following patents:
Australia: 2016314137 US: US 11,425,865 B2 EU (France, Germany, United Kingdom EP3341129)