Earlier seeding dates haven’t necessarily meant earlier last-frost dates.
It means many Manitoba farmers have been enjoying the benefits of a longer growing season, but they might also be facing an even greater risk of frost damage to young crops, says University of Manitoba soil science professor Paul Bullock.
Bullock researched last-frost dates in Manitoba to see if, as he expected, last-frost dates had moved two weeks earlier in the year to match the general movement of the growing season since the mid-20th century.
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“I was very surprised that it hadn’t,” he said in an interview during St. Jean Farm Days Jan. 7.
Indeed, last frosts of the spring still appeared to be happening around the third week of May, just as they had for many decades. The area around Altona, in the heart of Manitoba’s Red River Valley, seems to be experiencing earlier last frosts, but that wasn’t true in other locations that Bullock looked at.
It means farmers are generally able to get out earlier and seed a crop before they would have been able to 50 years ago, but they might be just as vulnerable to late May frosts.
However, he thinks the situation might not be quite as risky for farmers because his research only looked at frosts beginning at zero degrees rather than the hard frosts that farmers worry about. Perhaps some of the late frosts he was finding were not agriculturally important.
As well, some of the late frosts could just be part of the significant variability that exists during the prairie growing season, when the general two-week lengthening of the season can be hard to extract from yearly swings in conditions.
He hopes to investigate this issue further.
However, he said farmers still need to be aware that late May frosts continue to happen, and they can’t just assume the longer crop year means they are safer, sooner, from frost.
