While a rain in February is normally devastating for alfalfa, the heavy rainfall of this past month might have little impact, thanks to the snow cover on most fields.
John McGregor is the Farm Production Advisor with MAFRI in Steinbach and he says that the heavy cover of snow on most fields served to protect alfalfa from the rainfall and also extremely cold temperatures early in the winter.
“Snow cover and ice sheeting are the factors that I normally consider when looking at winter kill,” he says. “Snow cover insulates the soil and reduces winter injury to alfalfa crowns.” Alfalfa will tolerate temperatures of -12 C and the early snow cover has prevented the soil temperatures from falling below that.
McGregor explains that below this temperature the cells of the plant’s taproot freezes and ice crystals puncture the cell membranes. When the roots thaw the plant dies as water leaks from the roots cells.
The heavy blanket of snow on most alfalfa fields has served to insulate them from the cold temperatures but also served to save the crop in recent rains. The snow also served to protect the crop from ice sheeting that normally occurs when a rapid melt reduces the snow cover and refreezing turns to a layer of ice.
McGregor says that most fields had good snow cover and the rains of February should not suffocate the plants despite the ice cover.
He says the crop has survived two early challenges but is not out of the woods yet.
“Should we get an extreme cold spell before we get a couple of inches of snow there is the outside chance that soil temperatures could drop below the critical -12,” he says.
The other danger is that more warm weather in early March could cause ice sheeting.
He says that if we receive normal temperatures through the spring season the crop should be all right.
“If the thaw is normal and the water is absorbed into the remaining snow or ground there is little danger to the crop,” says McGregor.
Crops further south face more of a danger as melting in early spring can cause the plant to break dormancy and begin to grow and then another killing frost may hit.
For now, at least, the alfalfa crop seems to have come through the winter in good condition.
