By Jon Urness
I don’t think any of us are big fans of this year’s up-and-down winter weather conditions. Unfortunately, our alfalfa fields might not be big fans of it either. Wet fields in the fall, followed by big temperature fluctuations, ice and a diminished snow cover could lead to alfalfa winterkill.
The tricky part is, we won’t really know what (if any) winterkill we have until things start to green up in the spring, but it never hurts plan ahead in case you need to replant come spring.
Diagnosing winter injury
Let’s first discuss how we diagnose winterkill. This resource from the University of Wisconsin Team Forage provides good information on why winterkill occurs and how to diagnose it in your fields.
The first indication is plants that are slow to green up. If you see brown when other spots are starting to green and grow, it means you need to check your alfalfa stands for winterkill.
You want to see symmetry in the alfalfa plant. The buds for spring are actually formed in the fall. Some of those buds on the plant’s crown may be injured and some may not. The healthy buds will start growing early, but the injured ones won’t grow, giving the plant an asymmetrical shape. You’ll see shoots of different heights growing from the same plant, depending on when the buds were formed.
UW Team Forage tells us that root damage is the best indication of winter kill. Dig up the plants (4 to 6 inches deep) and take a look at the roots. Healthy roots are white and firm. Winterkilled roots are often gray with a water-soaked appearance just after the soil thaws. Once that water leaves, the roots will become brown, dehydrated and stringy. In addition, if more than half of the root is blackened with root rot, that plant will most likely die during the spring or later in the year.
If you need to replant…
Planning for the “worst-case scenario” can help you more efficiently take action come spring. Let’s say you have enough damage that you need to replace the plants. Determining when and what to plant depends on spring conditions and your forage needs. Again, UW Team Forage provides this helpful resource with further details to help you make a good choice and manage the crop.
If you will need more forage by early to mid-summer, consider planting a small-grain field pea mixture mid-April to mid-May. Peas can be mixed with oats, triticale, or barley, and improve quality and yield. This mix has a wider harvest window and should be harvested based on the maturity stage of the small grain.
Now let’s say you are replanting between mid-May and mid-June because spring is uncooperative and you can’t get in the fields or you want to take a first cutting before you plow up the field. In these cases, corn for silage is your best choice. Other options are sorghum-sudangrass hybrids (for silage or hay) or sudangrass (for hay or grazing). These crops do well in drought conditions and high temperatures, but won’t do as well in cool years. They can be harvested when the plants reach 30 inches in height.
What if you’re pushed back all the way to mid-June or mid-July? Corn planted during this time will not reach maturity, so sorghum-sudangrasses and sudangrasses become your best options. However, sorghum for silage can pose some harvest challenges when planted late, particularly in cooler-than-average years.
In all cases, work with your agronomist and nutritionist to determine what forage strategy and specific hybrids will best fit your field conditions and farm needs.
About the author: Jon Urness is the Vita Plus national forage specialist. He grew up on his family’s five-generation homestead dairy near Black Earth, Wis. and still lives there today. He graduated from the University of Wisconsin-Madison in 1977 with a bachelor’s degree in agricultural journalism. Since 1992, Urness has provided on-farm dairy nutrition consulting in southwest Wisconsin as a Vita Plus employee owner. He has also taken on the forage marketing responsibilities outside of the traditional Vita Plus market.