The growing season got off to a good start for many Saskatchewan producers, with warm April temperatures followed by significant rain on early seeded crops.
However, a hard frost on emerging crops across southern and central Saskatchewan has dealt a major setback for some growers.
Rosetown dropped below 0 C for six hours in the early morning of May 13, reaching as low as -5 C. Val Marie, in southwestern Saskatchewan, spent six hours below zero and was as cold as –4 C, while Saskatoon spent eights hours below zero and got as cold as –4 C, according to Environment Canada.
Weatherfarm stations reported temperatures as cold as -7 C in southern and central Saskatchewan.
Seeding progress was well ahead of average for this time of year, with 58 percent of the crop in the ground in southwestern Saskatchewan, according to the latest Saskatchewan crop report.
Some of this early seeded crop in southern and central Saskatchewan had already emerged and was likely damaged by the frost. Early seeded canola, flax and mustard are especially vulnerable to frost, and southwestern Saskatchewan is a mustard growing area.
Early seeded pulses will also likely be set back in areas that received prolonged frost.
“I talked to agronomists down there (southern Saskatchewan) early this week and they had peas that would be at the three node stage above ground, and they were getting ready to do some in-crop spraying,” Sherrilyn Phelps, agronomy and seed program manager with Saskatchewan Pulse Growers, said May 13.
She said pulse growers should be patient when deciding if they should reseed frost damaged crops.
“I have seen fields up in the northwest, lentil fields, that were badly frost damaged, but they came back no problem.”
Some pulse crops have growing points below the ground, which provides frost protection and ability to regrow.
“Fababeans are most tolerant, followed by peas and lentils,” she said.
Cereals can bounce back from a frost when they are early in development because their growing points are also protected below ground.
The risk increases later in their development because they are starting to switch to reproductive mode, and frost can damage that part of the plant, which forces the crop to restart.
However, crops that are able to regrow after a damaging frost may not reach full yield potential.
“Sometimes they can compensate and get back to normal growth and normal yield potential, but sometimes they won’t,” Phelps said. “Sometimes the frost weakens the plants, and other things can set in.”
Barb Ziesman, a provincial plant disease specialist with Saskatchewan’s agriculture ministry, said to assess the extent of damage to a mustard or canola crop, farmers should examine the entire crop one day after the frost and then re-examine it three to four days later.
“If the cotyledons are killed but the hypocotyl is still healthy, the plant will likely survive and will produce new leaves.”
However, she said the plant will likely die if the stem is pinched off or broken because the damaged stem will not be able to provide nutrients to the growing point.
Robert Klewchuck, Western Canada technical lead with Syngenta, said frost has damaged canola in southern Saskatchewan, but it was too early to gauge the extent of the damage.
The Canola Council of Canada says on its website that 20 to 40 plants per square metre can be adequate to produce a viable crop.
“Canola compensates so well, you get bigger stalks and bigger stems, and they fill in that area,” Klewchuck said.
“They (canola council) are saying before you panic, make sure you either have writeoffs of your low spots or you don’t meet these criteria (of less than 20 plants per sq. metre survived the frost).”