Weed control from the back of the combine

Prairie manufacturers are offering chaff collectors, and AAFC continues tests with the Harrington Seed Destructor

Mechanical weed control hasn’t been widely adopted in Western Canada but it soon will be, says Trevor Thiessen of Redekop Manufacturing in Saskatoon.

“We don’t have the same stress on the resistance issue that other parts of the world are seeing. In Canada, we’re five years behind Australia in terms of thinking about mechanical weed seed control options.”

Redekop has been working on harvest weed-seed control since 2015. Last year on two Saskatchewan farms, it tested the EMAR Chaff Deck, which confines weed seeds in chaff to lines behind the wheel tracks, and it plans more trials this year.

Thiessen refers to the Australian-made EMAR as an entry-level harvest weed-seed control (HWSC) option. It costs about $20,000 to $25,000 depending on the combine and is one of the only options currently available in Western Canada. Manitoba-based Tecfarm, in co-operation with Performance Feed Works, also offers a chaff cart line for hemp chaff collection and HWSC.

Redekop’s EMAR chaff deck delivers chaff to narrow bands within wheel tracks to reduce weed seed germination.
photo: Redekop Manufacturing

Chaff lines help with harvest weed control in two ways — the lines are easily targeted with herbicides, and potentially create a “composting effect” that tends to kill weeds if the piles are left on the ground.

Saskatchewan producer Derek Axten tested the EMAR system last year and intends to run it again this year. Because he practises controlled-traffic farming, Axten’s interest in the unit has more to do with tramline erosion management than weed control, as well as dust control for spraying. “On the weed front, it’s preventative maintenance,” he says.

Last year, Axten kept the chaff deck on one combine that he tried to consistently run on the line where his sprayer runs. The chaff spread at about a 10-inch width in the track. Thiessen says chaff lines typically fall between six and 10 inches wide, but Axten hopes to increase the width to about 20 inches. The system takes time to install, he says, but overall he’s been happy with its performance.

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Harrington Seed Destructor

In Canada, probably the best-known mechanical HWSC system is the Harrington Seed Destructor (HSD), which was developed in Australia and has been tested in Agriculture and Agri-Food Canada trials since 2016.

Breanne Tidemann, a research scientist in field agronomy and weed science with AAFC in Lacombe, is the lead on these trials.

A key part of Tidemann’s research initially involved evaluating the retention of various Prairie weed species to measure the effectiveness of HWSC methods. In field trials, Tidemann’s team determined that wild oat may become a better target for HWSC methods through use of swathing and early-maturing crop rotations.

Tidemann also ran indoor trials on stationary threshing machines to evaluate how the HSD handles factors like seed size and number as well as the type of chaff. In 2017, her team located 20 fields with known problems with weeds including wild oats, cleavers, hemp nettle, sow thistle and chickweed. They isolated weedy patches in each field.

The farmers didn’t make any changes in management in those areas. Tidemann’s team, with collaborators from PAMI, ran a combine and a Harrington Seed Destructor on the weedy sections. Both regular harvest and HSD treatments were used in these sections. The following spring, the team counted weeds to compare populations in the untreated regular harvest area with the HSD-harvested sections.

In fall 2018 they went back and harvested again, comparing weed counts in untreated versus HSD-harvested sections. They are currently completing counts following that harvest.

“The reason we’re doing it on the same place is that weeds won’t respond to the HSD right away because of seed banks. We didn’t expect to see a huge difference in the first year, especially where there are dormant wild oats,” Tidemann says.

Too early for conclusions

Preliminary results from the first harvest show one field with significant weed seed reductions and several others with lower weed counts, but Tidemann says there are some fields with higher counts and it’s too early to draw inferences about the HSD’s performance. Depending on weed species, it can take up to five years to see significant impacts on weed seed banks.

“Driving numbers down is faster for cleavers than wild oats, for example, because of their differences in seed dormancy. Conversely, wild oats would not last as long as wild mustard,” Tidemann says. “We’re hoping that by the end of the three years we’ll start to see a difference.”

The HSD used in the AAFC trials is already technically outmoded; in Australia, newer Harrington mill units are integrated right into the combine (these units are abbreviated “iHSD”). Its chief competitor is the Australian-made Seed Terminator, which sorts and crushes weed material by size. Other competitors are hitting the market in Australia.

Tidemann says one obvious market for the HSD is organic producers, who rely on mechanical versus herbicidal weed control.

“But for producers who don’t have a herbicide-resistance problem yet — and they will likely end up with this problem eventually — we’d encourage them to look into this option earlier as a way to prolong herbicide use,” she says.

“Considering how few truly new herbicides are coming to market, this is something that should be a consideration as a way to delay herbicide resistance. I don’t want to be dealing with glyphosate-resistant wild oats, and using this technology is a way to manage that selection pressure.”

This fall the team will conduct its third harvest, followed by final counts in spring 2020. “Hopefully by then we’ll have good news for producers,” she says.

Tidemann is also involved in a new systems trial that will combine crop rotation, seeding rates, with and without herbicides, and chaff collection to try and manage various weeds.

The project is being conducted at AAFC Lacombe, Lethbridge, Beaverlodge, and Scott; University of Saskatchewan and University of Manitoba, and is funded by Western Grains Research Foundation, Alberta Canola, Alberta Barley and SaskWheat Development Commission.

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