Ontario winter canola yields were very strong in 2020 giving us a good look at the incredible yield potential of the crop. Many producers reported yields over 3700 lb/ac and some watched their yield monitors jump over the 5000 lb/ac mark. The mild winter was likely a big part of that success, but Mother Nature did put the crop through an important test – late spring frost. This article outlines how the crop fared in 2020, and what to scout for after spring frost events.
During the last week of April, most winter canola growing regions were seeing temperatures above 15°C, and as high as 20°C in some areas. The canola was developing flower buds and elongating, advancing quickly towards first flower. May 8th to 13th was a much different story, however, and for a few days in a row the temperature fell below zero. In Harrow, the temperature dropped to -6°C on May 8th and stayed below zero for more than 24 hours. Top yielding fields in Blenheim also saw temperatures as low -4°C and spent many hours between zero and -3°C over a 5-day period. Other winter canola fields, such as those in Prince Edward and Perth Counties reached similar lows but for fewer total hours.
Winter canola can, of course, tolerate low temperatures while it is in the vegetative stages. Injury caused to canola by cold conditions during late vegetative stages in spring include:
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- Frost injured leaves
- Heaving and rotting where there is excess moisture or high clay content
- Death of main growing point and subsequent development of multiple stems
- Frosted plants killed in tire tracks when fertilizer was applied