But future weather will be just as variable as now so crops will still be at risk to frost, excess moisture and drought
Much of Western Canada is getting more frost-free days, on average, than it used to, which bodes well for expanding corn and soybean acreage.
“But please note in any given year the variation is 20 to 25 days,” University of Manitoba associate professor, Paul Bullock told the annual Manitoba Agronomists Conference last month.
An area could’ve had 115 first-free days last year and get 85 or 130 this year, said Bullock, who specializes in agrometeorology.
And while frost in late summer hurts most crops, corn and soybeans are especially vulnerable because they require a longer growing season to mature.
Citing data from Andy Nadler of Weather Innovations, Bullock said western Canadian temperatures are increasing. After reviewing 111 years of data, Nadler found the minimum western Canadian temperature has increased at more than twice the rate of the maximum. Most of that change occurred during the last 20 to 30 years. And most of the warming shows up in winter and spring, which adds to the growing season.
Long-term data also shows the West, on average, is getting more precipitation through more rainfall and less evaporation.
“But again, that’s average values,” Bullock said. “What kills us are the dry years and the wet years. So the fact that, on average, our (water) deficits are going down is fine, but what’s more important is probably the variability.
“When that deficit occurs, of course, is critical.”
Too much is worse
Crop insurance data from the Manitoba Agricultural Services Corporation shows that between 2003 and 2012, excess moisture was the biggest yield robber for both corn and soybeans, said Pam de Rocquigny, cereal specialist with Manitoba Agriculture, Food and Rural Development.
Too much moisture caused 42 and 53 per cent of the corn and soybean yield losses, respectively, followed by drought at 23 and 24 per cent.
Early frost accounted for five and seven per cent of yield loss in corn and soybeans during that period.
Early frost — once every 10 years or so — has hit Manitoba corn growers hard, including in the mid-1970s, 1982, 1985, 1992 and 2004, she said.
Following an early frost in 2004 MASC wrote off most of the province’s corn, much of which was also infected with mould, resulting in a provincial average yield of just 1.3 bushels an acre.
Nadler’s data shows between 1971 and 2000, most crop-growing areas of the West received at least 100 frost-free days 50 per cent of the time. But one in four years half of Western Canada gets fewer than 100 frost-free days and 10 per cent of the time almost the entire West gets fewer than 100 frost-free days.
Although the West, on average, has been getting warmer, data compiled by Nadler shows it’s not uniform. For example, Brandon’s crop heat units (CHU) are rising, on average, but they are declining at Minnedosa. Lethbridge is getting more and Medicine Hat is getting fewer.
The biggest increase in CHU has been in the Peace River District of northern Alberta, while there has been no increase along the Manitoba-Saskatchewan border.
Climate models predict Western Canada’s average temperature will rise 2° to 4° by 2045 to 2065, Bullock said.
“That would suggest we are going to continue to see this lengthening of the growing season,” he said. “So that’s a good thing. Plus, we’re likely to have larger accumulations of things like corn heat units. So that’s positive.”
But the models don’t do a good job predicting precipitation, Bullock added. They call for as much or slightly more precipitation, but more of it will fall when it does come.
“Kind of the exact opposite of what we’d like to see in agriculture,” he said. “That’s not a great thing.
Western Canadian farmers can expect more frost-free days and more heat units, on average, in the future, but just as much variability as now along with possibly more floods and droughts, Bullock concluded.