Date: May 19, 2009

Author: Glenn Friesen, Forage Specialist, Crops Branch, Manitoba Agriculture, Food and Rural Initiatives, Ph: 204-745-5672

The disappearance of snow earlier in the winter left some fields exposed to the elements, which could present the possibility of winterkill damage to alfalfa stands. Cold conditions after snowmelt, combined with ice encasement may create the possibility of overwintering damage in alfalfa stands.

Producers are encouraged to evaluate stands in the spring for overwintering damage. Low areas in the field are more susceptible than higher areas to flooding and ice encasement damage. If areas in the field have been flooded out, it may be possible to sod-seed to re-establish alfalfa in these areas, depending on the age of the stand. In the cast of alfalfa, a stand two years or older should be rotated to another crop to avoid autotoxicity.

For overall stand assessment, the measurement of stand density in terms of number of stems per square foot is the usual recommended measure of stand productivity. In a pure alfalfa stand more than 55 stems per square foot is considered as no limitation to yield, between 40 and 55 will have some yield reduction expected, and stands less than 39 stems per square foot should raise questions about whether the stand should be replaced.

For grass and alfalfa mixtures, consider the ratio between grass and alfalfa before applying the above guidelines to the stand evaluation.