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Killing frost Friday would damage W. Man. crop

After the weekend, warmer, drier weather is forecast until the end of September

Some weather models point to widespread frost Friday (Sept. 12) in western Manitoba.

A killing frost Friday morning will damage a lot of crops in western Manitoba, including cereals and canola, says Lionel Kaskiw — and that’s what the forecast is calling for.

“We needed at least until the third week of September or the end of September (without frost) and we’re getting (frost possibly) the second week of September so there’s a lot of crop that’s going to be affected,” Kaskiw, a Manitoba Agriculture Food and Rural Development (MAFRD) farm production advisor based in Souris, said in an interview Wednesday.

Corn in much of the province, including the Red River Valley, would be damaged by a hard frost too.

Environment Canada is forecasting frost early Friday morning for much of southern Manitoba. Lows could dip to -4 C in the west and -3 C in the south Red River Valley including Deerwood, Morden, Morris and east to Steinbach.

But Mike Wroblewski, MAFRD’s ag weather specialist, said Canadian and American weather models predict some parts of western Manitoba could see lows of between -5 and -10 C.

“So far Friday morning has the biggest risk of frost and it looks pretty widespread,” Wroblewski said Sept. 10 during a MAFRD webinar.

“For those guys along the Saskatchewan border three days out of four it’s looking below 0 C (lows) so the risk is pretty high out there that something is going to come out of it.”

Even lows of -3 C will cause considerable crop damage in western Manitoba, Kaskiw said, as most crops were seeded late because of the wet spring.

Growing degree days are close to normal in that region and little below normal in the Morden-Winkler area.

Many farmers are swathing their immature canola now because of the frost threat, he said.

To avoid frost damage in the swath canola seed moisture needs to be 25 to 20 per cent, therefore Kaskiw expects some canola will still be damaged in the swath if it freezes Friday morning.

“A lot of cereal crops were already sprouting standing and there’s some mildew,” he said. “If we get a frost it will probably affect most of the cereal crops I would think that are still out there.

“One farmer told me Friday if it froze he’d lose half his crop.”

Western Manitoba soybeans, which are in the R-6 (full seed) to R-6.6 stage, will suffer reduced yields and quality, Kaskiw said.

Corn, which hasn’t reached the dent stage in the west, will also be hard hit by a killing frost, he said.

Corn is in the dent (R-5) stage in much of the Red River Valley, therefore a killing frost will reduce its yield and quality too, said MAFRD cereal specialist Pam de Rocquigny.

Corn in the R-5 stage is around 50 to 55 per cent moisture. At 30 to 25 per cent moisture frost does little damage to corn.

In an earlier interview MAFRD farm production advisor Dennis Lange said most of the Red River Valley’s soybeans are close to full maturity but a killing frost would reduce yields and quality in some fields.

Most cereals and canola in the Red River Valley are mature enough to avoid frost damage.

Frost is a fickle enemy. The impact can vary depending on how long the freezing temperatures last, wind speeds, humidity, topography (cold pools in lower areas), the type of crop and its maturity.

And it usually takes a few days before the impact can be assessed, although damage shows up quicker after a long, hard frost.

Often frozen cereals and canola can still be harvested and sold, but at lower grades, returning less per tonne.

Frozen whole cereal crops and corn can also be salvaged for livestock feed. However, they should be tested for nitrate levels, which are potentially toxic, said MAFRD beef specialist Juanita Kopp.

Crops that have suffered stress during the growing season or were heavily fertilized with nitrogen, can contain high amounts of nitrate when killed prematurely by frost. Stresses include drought, heat, flooding and even herbicide drift. Farmers planning to feed frozen crops should test to find out the nitrate content, she said. Feed with a lot of nitrate can be blended to avoid problems.

Frozen corn can be ensiled for future cattle feed or directly grazed. But that’s easier said than done, Kaskiw said. If there’s a widespread frost there won’t be enough person-power to ensile all the corn that’s damaged. And feeding to grazing cattle requires fencing and a source of water.

A killing frost (-2 C or colder) this week would be earlier than normal for most of agro-Manitoba (see map below), but not out of the ordinary.

After the weekend the models are predicting warm, drier weather for most of Manitoba until the end of the month, Wroblewski said.

— Allan Dawson is a reporter for the Manitoba Co-operator at Miami, Man.



About the author


Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.



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