Mechanical harvest weed control

The Harrington Seed Destructor is a chem-free way to chew up weed seeds at harvest time

The three trays on the left represent 10,000 canola seeds that were not put through the Harrington Seed Destructor before researchers grew them out. The two trays on the right show the low germination rate of 10,000 canola seeds after researchers ran them through the Seed Destructor.

Recent research into harvest weed seed control is yielding some promising results.

Breanne Tidemann, Agriculture and Agri-Food Canada research scientist based in Lacombe, has been studying how effectively the Harrington Seed Destructor chews up weed seeds. Tidemann and her colleagues collected chaff from a bag attached to the back of a combine, then ran the chaff and weed seeds through the seed destructor.

Researchers tested kochia, green foxtail, cleavers, volunteer canola, and wild oats in barley chaff. They also tested different volumes of chaff and seed, and seed sizes, in the Seed Destructor. Each treatment was repeated four times.

Statistically speaking, there were differences between how the Harrington Seed Destructor performed in each treatment. But those differences will make little difference to farmers in the field. The Harrington Seed Destructor destroyed 95 to 98 per cent of the seeds, no matter the seed type, size, number, or amount of chaff, Tidemann says.

“It just seemed to work.”

Evaluating seed viability was a bit of a challenge. Growing seeds with the full milled material, which includes milled chaff and seeds, “really promotes fungal growth to the point that you can’t actually find seeds because they’re decomposing,” says Tidemann.

Instead, researchers did a multi-stage cleaning process, which allowed them to grow out the seeds, minus the excessive fine chaff material.

Not every western Canadian weed will be a perfect fit for the Harrington Seed Destructor. Tidemann outlined three conditions for harvest weed seed control to work:

  1. Weed seeds must be on the plant at harvest time.
  2. Weed seeds need to be at the right height so they can be collected by the combine.
  3. The weed must be harvestable, and must go through the combine.

For example, kochia tends to tumble right over the header, meaning it might not be a good candidate for the seed destructor. And previous research by Tidemann and her colleagues found that wild oats often shatter before harvest, so harvest weed seed control alone won’t control all wild oats.

Next steps

The next stage of her harvest weed seed destructor research is already underway. During harvest 2017, researchers started field-testing a tow-behind unit of the Harvest Weed Seed Destructor in 20 fields in the Lacombe area. Tidemann and her colleagues are working in peas, canola, and wheat. Canola and wheat will include swathed and straight-cut crops.

“Each of those fields has a weedy area in it, and the size of the trial in each field was determined by how big of a weed patch we could find and how consistent those weeds were,” says Tidemann.

Weeds in the fields include wild oats, cleavers, chickweed, hemp nettle, sow thistle, and buckwheat.

Researchers harvested the weedy areas both with and without the Harrington Seed Destructor, and they’ll do the same for the next two years. In spring 2018, they’ll start counting weed seed emergence in both treatments before the farmer sprays. Tidemann says they’ll also do seed bank weed seed density collections in both treatments in 2020.

Tidemann has learned a few practical lessons from her first harvest with the tow-behind Harrington Seed Destructor:

  1. Air velocity is important. If there’s not enough air velocity, the equipment will plug.
  2. Don’t harvest green or wet material. It doesn’t grind as well, and it tends to plug.
  3. The tow-behind unit doesn’t handle hills well. The tubes attaching the combine to the Harrington Seed Destructor tend to accordion.

But farmers interested in harvest weed seed destruction can skip the tow-behind units entirely. Integrated versions of the Harrington Seed Destructor and a rival brand, the Seed Terminator, are now available. Both products were developed in Australia, and both attach to the combine. The Harrington Seed Destructor is powered hydraulically and uses a cage mill. The Seed Terminator is mechanically driven and uses a hammer mill.

Australian research has shown that the tow-behind and integrated Harrington Seed Destructors are equally effective at destroying weeds. That means Tidemann’s research on the tow-behind unit will apply to the integrated model as well.

Tidemann hasn’t done any work with the Seed Terminator, but that doesn’t mean researchers are recommending one brand over another.

“We’re looking at the whole concept of harvest weed seed control, not just the product.”

About the author

Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.



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