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In-crop mechanical weed control

Controlling weeds mechanically can help overcome Group 2 resistant weeds in pulses

The best time to deal with a weed such as kochia is when it's small.

Group 2 resistant weeds are an annual problem for lentil producers. But there are a few outside-the-box methods that may give farmers better control than herbicide alone.

University of Saskatchewan grad student Alex Alba led a study looking at three in-crop mechanical weed control methods, including:

  1. Tine harrows;
  2. Rotary hoe; and,
  3. Inter-row tillage.

Alba used each weed control method alone, and in combination with the others. In an interview at Saskatoon’s CropSphere, Steve Shirtliffe, University of Saskatchewan researcher, said each one has its own niche.

“The rotary hoe works well controlling weeds when they’re very tiny — just emerging or just before emergence,” Shirtliffe said.

The harrows are used a bit later in the spring. “It can be a good weed control tool but it can also hurt the crop a lot.”

And finally, once farmers can see the crop rows, they can till between the rows. Shirtliffe added that farmers till between rows as narrow as 7.5 inches.

In the end, all of three methods “did a decent job of weed control,” said Shirtliffe. “We were getting at least a 50 per cent weed biomass reduction by using anything.”

Shirtliffe said that weather would be a big factor on farms. However, Alba’s study found that an early rotary hoeing followed by inter-row tillage later in the year consistently worked well, controlling upwards of 75 per cent of the weeds.

In another study, researchers looked at using the rotary hoe with Edge to control kochia. Edge is also known as ethalflurulin, and is a Group 3.

Shirtliffe cautioned that they only had one site year of data for that study. But that limited data did show that fall-applied Edge can work on kochia, as can the rotary hoe.

Researchers are now starting to extend that mechanical weed control work beyond pulses. They are also looking at how to control weed seeds as more of a remedial action. For example, researchers are looking at clipping the flowers and new pods of mustard and other weeds that top the lentil crop.

“And we’ve found that it can be quite effective in reducing weed seed production,” said Shirtliffe, adding that they only have one year of data so far.

Researchers are also using an implement that wipes herbicide onto tall weeds. So far, results have been mixed, and it’s too early to make recommendations to producers, Shirtliffe said.

However, some products don’t work at all, he said, because they hurt the crop. Others “seem to work okay, but we need more research on them to find out,” said Shirtliffe.

Managing kochia in saline land

At CropSphere in Saskatoon, Steve Shirtliffe, University of Saskatchewan researcher, talked about kochia nurseries — saline spots that grow kochia, and little else, every year. Typically farmers try to seed those unproductive areas, and then try to spray out the kochia.

But ultimately trying to farm that saline land this way is “very risky behaviour for the entire ag industry,” said Shirtliffe.

“You’re doing a breeding trial. You’re a kochia breeder. And you’re selecting for herbicide resistance.”

Shirtliffe said farmers should try something different, such as doing something “spatially to isolate those parts of the field and at least mow them down before they go to seed.”

Ultimately, Shirtliffe would like to see a farmer pull a saline area out of production. That might mean seeding it to grass in the long term, rather than seeding it and hoping it will produce a good crop every year.

“It’s not ever going to be a good crop.”

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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