Watch alfalfa fields for winter damage

By Nathan Winter — U of M Extension Educator

Will April’s chill spell cause “winter” kill? State Extension Forage Specialist Paul Peterson posted some discussion recently at http://www.extension.umn.edu/cropenews, discussing conditions around Minnesota and what to watch for when spring comes around again. Here are some of the points Paul makes (with some editing).

The potential for winter injury is always difficult to predict. Perhaps the most useful point of this discussion is to get out into alfalfa fields to see how they’re doing over the next two to three weeks.

In the northern two-thirds of Minnesota, recent weather has been favorable for alfalfa survival. Early reports indicate that little if any alfalfa broke dormancy in March. And most of the northern two-thirds of the state received an insulating blanket of snow prior to the cold snap. There may be more concern in low areas where water may have pooled and frozen for extended periods during the winter, on wind-swept hill tops, or south slopes where snow melted ahead of cold winter weather.

In the southern third of Minnesota, however, alfalfa did begin to break dormancy in late March, and did not have insulating snow cover during some of the cold weather in early April. Healthy, well-hardened, dormant alfalfa is very cold tolerant; crowns and crown buds are thought to be able to withstand soil temperatures as low as 5 to 15 degrees.
Plant stubble and residue helps to buffer cold temperatures along with holding snow. From April 5 through April 8, soil temperatures at depths of 1 and 5 centimeters in bare soil on the St. Paul Campus dropped to lows of 20 and 27 degrees respectively; and reached highs of 54 and 40 degrees.