Did We Experience Alfalfa Winterkill?

Did We Experience Alfalfa Winterkill?

Following much warmer than normal weather in March the weather in the first 11 days of April has been colder for most of the Midwest, especially at night. Cold enough to possibly kill newly established fields. How do we know if stands are irreparably harmed? Let’s look at some data and charts to determine whether to plow up a field or not.

Newly Established Fields Newly established fields planted in the latter half of March may have emerged by April 4 when the very cold weather blasted our region. Alfalfa that has emerged is in great risk. According to the booklet How an Alfalfa Plant Develops published by the Certified Alfalfa Seed Council "air temperatures of 26° or lower for only a few hours can kill an alfalfa seedling when the second trifoliate leaf has just emerged." So newly emerged fields are at great risk. 

 What Do We Do Now? Wait. We will really know nothing until the air temperatures warm up into the 55°-60° range and the alfalfa starts to re-grow. At that time dig some plants to check the crown and tap root. Are they healthy looking? Or, are they moisture laden and "mushy"? Evaluate field to field and also within each field. Also evaluate the stand. The chart below is standard for evaluating the strength of your stand. While you are at it check for the presence of winter annual weed pressure. A poor stand that has weed pressure would be a great candidate to become a corn field!

 What if I Have A Poor Stand? If your alfalfa field has suffered winterkill or is a poor stand you should consider inter-seeding more alfalfa in right away, or wait until this fall to add more alfalfa seed. If you wait until fall to plant more alfalfa we still have plenty of time to add Feast II Italian Ryegrass to the newly seeded fields so you don’t lose yield or quality for the first season. Consider planting up to 20#/acre of Feast II. This August of early September go ahead and spray out the Feast II (after the second cutting) so you can re-establish more alfalfa. Add more grass after the alfalfa is well established.

What Can I Do To Help Prevent Future Winterkill Problems? Planting winterhardy alfalfa varieties may help. Maybe most importantly will be to keep your fertility levels (especially P and K levels) high. Well fertilized fields will have much stronger stands and healthier plants. In some years there may be nothing at all that will prevent winterkill.


 New Seeding Stand Evaluation Guide
Less than 10 seedling per sq ft = Poor
Between 10-15 seedlings per sq ft = Marginal
Greater than 15 seedlings per sq ft = Adequate

Stand Density-Established Stands
Stand density (Stems/sq ft) Action
>55 stem density not limiting yield
40-55 some yield reduction expected
<39 consider replacing stand

This is a great article that was written by Dave Robison,

Agronomist/Seed Marketing Manager for The CISCO Companies