NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

March 25, 1999

NDSU Researcher: Check Alfalfa Fields Now

Significant amounts of snow melt occurred in North Dakota in late November and early December and again in February. The above-normal temperatures that produced these two melts, coupled with the bare ground left by the retreating snow, could prove to be troublesome for the region's alfalfa producers. For that reason, an agronomist at North Dakota State University is advising producers to monitor their alfalfa fields for early signs of winter injury or perhaps winter kill.

"Those two warming periods almost certainly must have lowered the dormancy of alfalfa plants," says Dwain Meyer, NDSU plant sciences professor.

The occurrence of winter injury or winter kill will depend on two key environmental factors: when the snow cover opens and how late in the spring temperatures dip to 10 F or colder. Symptoms of any potential problems should appear as soon as fields start to turn green, Meyer says. Alfalfa growth should occur along with the development of cool-season weeds. If not, it's likely the alfalfa was winter killed.

However, Meyer cautions producers about "false green-up," a condition where a severely injured plant will initiate growth from the stored carbohydrates in the crown, but once that energy is depleted, the plant dies. He says, "We don't see that much false green-up around here."

Another way for alfalfa producers to determine whether damage has occurred is to inspect the root systems of plants in suspect areas of the field. A yellowish tap root that feels soft to the touch signals winter kill.

"The root system should be white and firm," Meyer says.

In winter-injured plants, the central part of the tap root is the first to receive damage, followed by smaller roots. It's possible for some alfalfa plants to initiate growth and be supported by the smaller roots, but Meyer is unsure of whether those secondary roots will eventually die. Damaged tap roots will turn black from infections by Fusarium root rot.

Alfalfa producers with winter-killed stands that are at least two years old should re-establish their alfalfa elsewhere and use the old alfalfa ground for planting a cereal crop that can utilize the nitrogen produced by the alfalfa. Meyer says another option would be to no-till an annual forage into the old alfalfa ground.

In alfalfa fields that have been partially killed, Meyer suggests seeding oats into the dead spots. He says, "Don't even plow it. No-till it inan inch or an inch and a half deep. The resulting oat-alfalfa mixture will make an excellent feed for beef cows."

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Source: Dwain Meyer (701) 231-8154

Editor: Dean Hulse (701) 231-6136