Short rotations | Crop disease such as blackleg and clubroot show the folly of ignoring agronomics
As a consistent high profit generator, canola-seeded area has doubled in the past 10 years, mostly by reducing rotations from once every three or four years to once every other year or continuous.
However, short rotations encourage development of fungi and weeds able to overcome disease resistance in crops and herbicides. With the right weather circumstances last summer, many farmers saw crop disease severely limit yield.
Western Producer reporters Robert Arnason, Barb Glen and Robin Booker have compiled this special report looking at how canola’s success encourages pests that threaten its future.
Ed Rempel paused before answering the question: are two-year canola rotations sustainable over the long term?
“Heck, no,” said Rempel, who farms near Starbuck, Man., and is president of the Manitoba Canola Growers Association.
“I’ll speak to my farm, where I’ve been one in two for years and years and years…. Up until four years ago I was getting away with it. Since about 2008, I found out that I’m slowly losing the battle. I’m losing yield…. My canola average is going down.”
Rempel took a chance this spring and planted canola on a field with history of blackleg. He assumed things would work out if he used a resistant variety and sprayed for the disease.
They did not.
“On the north 80 acres of that field, the blackleg showed up again … and it (yield) was about 12 to 15 bushels less (compared to the remainder of the field),” he said.
Rempel is done pushing canola rotations.
“I no longer can do it, and it will be sorting itself out on farm after farm,” he said.
“I think everyone in Western Canada has been pushing their rotations…. In the (Red River) Valley, maybe some of those chickens are coming home to roost.”
Barry Chappell, who farms 2,500 acres of grain and oilseeds near Hamiota, Man., is taking a different approach.
Chappell has maintained a two-year canola rotation on his farm since 1997 and expects it will be viable going forward.
“Could we potentially have higher yields out of three (year rotations)? I’m not going to dispute that,” said Chappell, who also runs Chappell Seeds.
“(But) through the years, with the improvements in genetics in the canola, along with decent fungicide options, I personally feel I can manage disease in canola far better than I can in a cereal on cereal rotation, with fusarium and all those issues.”
According to crop insurance figures, most Manitoba farmers agree with Chappell that two-year rotations are manageable. More than 50 percent of the province’s canola fields are now grown after a one-year break from the oilseed.
The rotation squeeze is even more severe in Alberta’s Peace River region. In 2009, canola was grown on 370 fields after no break, 390 fields had a one year break and only 15 fields had a two year break, based on data from the Alberta Financial Services Corp.
Raymond Blanchette, who farms 1,400 acres near Falher, exemplifies the trend.
“It’s wheat-canola-wheat-canola,” he said.
“I change varieties every couple years. Some of the neighbours, it’s canola-canola-wheat, but they usually go with Liberty Link one year and Roundup Ready the next.”
Blanchette, a director on the Alberta Canola Growers Commission, has heard agronomists recommend longer rotations to protect blackleg resistance in seed varieties and limit other disease and insect pressures.
However, he hasn’t seen major effects on yield from his short rotation. He attributes it to successful research and plant breeding.
In southern Alberta, Stephen Vandervalk of Fort Macleod has been growing canola every other year on much of the family farm.
“You make more money. There’s in general less quality issues. The only real risk is wind damage, for us anyways. That’s why we grow it more than anything.”
Vandervalk, president of Grain Growers of Canada, said many canola growers bank on crop research and improved genetics to protect them from risks related to short rotation.
And even if yield suffers, the per acre returns are still higher than from most other crops.