Frost impact still unclear

A portion of western Canadian growers are reseeding their canola after frost hit almost all of Manitoba and most areas of Saskatchewan May 27.
However, it seems like severe damage may be limited. 
In many areas canola plants were just beginning to pop out of the soil.
Justine Cornelsen, a Canola Council of Canada agronomist in Manitoba, checked a few canola fields in the western part of the province yesterday.
She did see plants with burned cotyledons, but the fields she looked at were salvageable.
“The growing point (was) still green (on many plants),” she said. “That’s a good sign. That’s all you really need is for that hypocotyl tissue (central growing point) to be green. That means it’s going to hopefully push through a true leaf…. If that tissue survived and is green and vibrant, it means that plant should pull through.”
Manitoba Agriculture weather data from the morning of May 27 indicated that temperatures dipped below zero in every agricultural zone of the province. 
Many areas had temperatures of -1 to -2 C, but temperatures in northwestern Manitoba and the northern Interlake were more extreme. In those regions the thermometer sank below zero for six or seven hours — with minimum temperatures hitting -3 to -4 C
For instance:
• Arborg recorded six hours below zero, with a minimum temperature of -3.1 C
• Grandview had eight hours below zero, with a minimum of -4.6 C.
• Laurier dropped to -3.2 C and it was below zero for eight hours.
“Minus four for four to six hours is a fairly heavy frost for a significant amount of time,” said Anastasia Kubinec, Manitoba Agriculture’s manager of crop industry development.
The story is similar in Saskatchewan. There were geographic pockets where the temperature sank to -3 C and lower.
Southeastern Saskatchewan suffered the coldest temperatures.
“Canola was hit the worst (in the region), wiping out early seeded crops and will likely impact pulse-cereal yield potential going forward,” FarmLink Marketing Solutions said in a crop conditions update.
With frost, though, it’s all about timing. The majority of canola acres were seeded after May 15 and soil temperatures were cool this spring.
So, for many growers, the May 27 frost arrived before canola plants had emerged or just as canola plants were popping out of the ground. 
“I would like to think a lot of them (escaped) the frost because they were still emerging,” Cornelsen said about the situation in Manitoba.
The circumstances are not the same as 2015, when a frost in early June smoked canola fields across Manitoba. That year, nearly a million acres of canola were reseeded because of frost damage.
“Completely different situation (this year). That was a June 1 frost. We had a bunch of the crop up and out of the ground,” Cornelsen said, adding that temperatures dipped to -7 C during the 2015 frost.
At this point it’s hard to estimate how many acres of canola will be reseeded. Some growers are choosing to reseed and others are weighing their options.
 “I think that’s the real big question right now. If you look at some of the older research, it shows you’re better off to leave that (frost damaged) crop,” Cornelsen said. 
“In the fields I was in, they were still averaging five to six plants per sq. foot. So, they did lose one or two (plants) to frost, but there’s still lots to work with there.”
In other cases, there might only be one or two viable plants per sq. foot. That makes the decision more difficult.
Even if a producer only has a few plants per sq. foot, keeping the crop might be a better choice than reseeding this year. Soil is short of moisture, and reseeding into dry soil isn’t a great option.

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