While it seems like most alfalfa fields are greening up quite nicely this spring, there have been a few reports of winter injury in alfalfa stands, especially if stands or parts of stands may have been covered by sheets of ice during the winter.
Take some time now to evaluate stands for any winter injury and determine if any action is needed. Table 1 and Table 2 below can be used to help determine what type of action may be warranted in a field. Possible remedial actions could be doing some patch-work seeding, keeping the field for a first crop cutting and then rotating, or rotating fields entirely.
Table 1. Suggested plans of action based on observations and alfalfa field conditions.
Table 2. Recommended plant counts per square foot in either pure alfalfa or alfalfa-grass mix based on the age of the stand. Source: Modified from Table 2 in PM 1362 “Evaluating Hay and Pasture Stands for Winter Injury”
Overwintering perennial forage grasses often survive better than winter hardy legumes. However, orchardgrass and ryegrasses are more susceptible than other perennial forage grasses to winter injury. Visual evaluation of grass regrowth and health of crown tissue is suggested when evaluating winter survival of pastures.
Reseeding in hayfields or pastures might be needed. It is not recommended to reseed alfalfa into stands that are two years or older due to the likelihood of autotoxicity. Overseeding or drilling grasses or red clover into thin or winter damaged stands ideally would be done before May 1. Seeding after mid-May increases the likelihood seeds will germinate but less frequent rainfall will allow the soil to dry out before roots are deep enough to reach moist soil, killing the seedlings.
Additional resources related to alfalfa winter injury and managing winter injury:
Rebecca Vittetoe Field Agronomist in EC Iowa
Rebecca Vittetoe is an extension field agronomist in east central Iowa. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors.
Areas of expertise include agronomy, field crop production and management of corn, soybeans, and...