Prairie farmers have successfully diversified the kinds of crops they grow.
Now they need to start thinking about diversifying the “life cycle” in their fields, says an expert in weed control.
That means getting away from the routine of seeding and harvesting crops at the same time every year and spraying them with the same herbicides.
Weeds are too smart for that, said Neil Harker, a weed scientist with Agriculture Canada in Lacombe, Alta.
“We always look at how to kill weeds, but we seldom look at why they’re there,” he said. “Generally it’s because we don’t have enough diversity.”
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He told farmers attending the annual conference of the Saskatchewan Soil Conservation Association there are lots of things they can do to disrupt that predictable life cycle.
They can plant a winter cereal or a perennial forage for a couple of years. They can adjust planting dates for summer crops and increase seeding rates to produce a healthy crop stand.
They can select varieties that are the most competitive with weeds and they can diversify their rotations.
None of these strategies will make weeds disappear tomorrow, but there’s no doubt that over time they will result in less dependence on expensive herbicides.
“You’d have to be in it for several years before you drive the weed population down, but I definitely think it is a money saver for farmers over the long term,” said Harker.
Doing the same thing every year will almost guarantee ongoing weed problems. The seeds that survive and go into the seed bank every year are by definition seeds that will survive and prosper in that production and management system.
“If they are met with a crop the next year that comes up the same way, they’re just going to thrive again,” Harker said in an interview after his speech.
The traditional emphasis on spring-seeded cereal crops is the reason that wild oats, wild buckwheat and foxtail are the predominant weeds on the Prairies, he said.
On the same panel was a farmer who does many of the things Harker talked about.
Warren Kaeding, who farms near Churchbridge in eastern Saskatchewan, said it’s a never-ending battle trying to stay ahead of weeds.
“As we get one species under control, another will come along to take its place that will be just that little bit more difficult to control,” he said.
Kaeding plants around 5,000 acres, with 3,500 acres producing pedigreed seed.
He grows a wide array of crops including winter and spring wheat, triticale and fall rye, perennial ryegrass and fall-seeded canola, two-row barley, peas, pinto beans, flax, canola, oats, sunflowers and even pumpkins.
He studies each of his fields early in the growing season, taking comprehensive notes on the weed species present, population density, location and any significant patterns that might emerge.
While Kaeding makes extensive use of herbicides, he also uses a number of cultural practices that help keep weeds in check.
For example, sunflowers are planted in late May and sprayed with Roundup just before emergence in mid-June, which allows significant weed growth to develop and be controlled before the sunflowers come up.
As well, cereals are planted shallowly at a 15-20 percent heavier seeding rate than normal to ensure quick emergence and reduce the effect of herbicide persistence on seedlings.
Harker said he suspects the typical weed control balance in Western Canada is about 90 percent herbicide and 10 percent cultural practice.
“I don’t think I can give a figure as to what it should be,” he said. “I’m just trying to encourage farmers to do more cultural control.”
While herbicides will remain an important tool in any weed management program, it is clear that herbicides have been overused, resulting in the development of resistant weeds.
“The major ecological concern for farmers is the threat of widespread resistance to wild oat herbicides,” he said, adding that the ability of weeds to select for resistance ceases only when herbicides are no longer used.
