36 | Advancing Seed in Alberta deal with, or delay, a weed problem. He firmly believes that reducing the number of seeds entering the seed bank, and/or manipulating where they enter the seed bank, are two important tools for managing an ever-changing composition of weeds in any field. Current Research In 2017 and 2018, Tidemann and her team experimented with seed destruction in 20 producer fields in Alberta, and the trials will continue for two more years to determine the effects of this technique on surviving populations. “We took weed counts this spring, but that data isn’t summarized yet.” She’s using the Harrington Seed Destructor (HSD), invented in Australia, a device that’s towed behind the combine and features a cage mill that crushes the chaff — and the weed seeds the chaff contains. Speed of chaff movement is critical for the system to work best, and Tidemann has also found that farmers should wait until green or tough material has had a chance to do some drying. The tow-behind HSD model is actually no longer on the market, but the firm offers the Integrated Harrington Seed Destructor (iHSD) that mounts directly onto the combine. Australian researchers have shown that the HSD and iHSD provide similar results. There is also a competitor called the Seed Terminator. As far as Tidemann is aware, there are no published research results about the performance of the iHSD or its competitor, but she says a number of producers are using the iHSD in Australia, and there is also one being used in Canada, north of Saskatoon. She’s heard that both of the mill systems on that unit ran into some wear issues last harvest, and that some modifications are being tried. Mechanics of Destruction In order for a seed destruction system to be effective, the weed seeds obviously need to be in the chaff. Cleavers and volunteer canola work well, but chickweed seed doesn’t because it’s so close to the ground and producers don’t want to chance equipment damage by cutting at that level. Tumble weed also ChaffLiningResearch inAustralia Chaffliningisthepracticeofconcentratingchaffin anarrowrowbetweenstubblerowsdirectlybehind theharvester.AnAugust2018UniversityofWestern Australiareportstatesthatuseofchafflininghasrisen rapidlyinthatcountryoverthelasttwoyears.“Asurvey ofWeedSmartsubscribers,”statesthereport,“showsthe percentageofgrowersusingchaffliningincreasedfrom 6%in2016to26%in2017.”WeedSmartisanindustry- ledinitiativetoenhanceon-farmpracticesandpromote thelong-termsustainabilityofherbicideuse. RecentstudiesheadedbyAnnieRuttledge,fromthe DepartmentofAgricultureandFisheriesinToowoomba, Australia,showthatuseofchaffliningorchaff tramlining—whenchaffmaterialisconcentratedon dedicatedtramlinesincontrolledtrafficfarmingsystems —doesconcentrateweedseedsintoanarrowarea,and thatheavylayersofchaffleadtobettersuppressionof weedemergence. “Smallseededbroadleafweeds,forexamplecommonsow thistle,aremoreeasilysuppressedthangrassweedswith largerseeds,suchasannualryegrass.Thicktramlines andchafflinesreduce,butdonotprevent,weed emergence,soothermeasuresmaybeneededtocontrol weedsintramlines/chafflines,forexample,sprayingthe tramlineswithashieldedsprayer,”saysRuttledge. Formoreinformationgotohttps://weedsmart.org.au/ how-chaff-lining-works/andhttps://ahri.uwa.edu.au/ chaff-liningtoo-good-to-be-true/. Invented in Australia, the Harrington Seed Destructor crushes the chaff — and the weed seeds — the chaff contains. Photo courtesy of Dr. Neil Harker. “Seeds that enter the combine may be spread up to several hundred feet away from the initial mother plant, which for patchy weeds, or seeds from a newly-introduced herbicide- resistant biotype, represents an efficient method of establishing new patches and rapidly becoming a widespread field problem.” — Ian Epp