Farmers urged to check for winter injury in hay stands
By Jean Caspers-Simmet
Date Modified: 05/28/2013 8:02 AM
DECORAH, Iowa — Brian Lang, Extension field agronomist in Decorah, has fielded several calls about alfalfa winter injury.
"There was some alfalfa winter-kill, with the majority occurring on south-facing slopes of alfalfa fields seeded in the spring of 2012," Lang said. "There was also some Italian rye grass winter-kill on south-facing slopes. The winter-kill was rather spotty, anywhere from a few square yards to a few acres."
Some damage could be corrected with interseeding and other damage was so severe fields were transitioned out of alfalfa.
The dead plant's crown and/or taproot just below the crown was soft and spongy. When sliced open, the tissue from the winter-killed plants was soft and yellow, not firm and cream colored as it should be.
He also received reports of alfalfa winter-kill on some older stands.
"So far, reports on older alfalfa stands have one thing in common," Lang said. "They were managed quite intensively last season, being cut on as little as a three-week harvest interval with six cuts for the season. The 2012 warm temperatures and drought issues caused alfalfa to flower sooner than normal."
Lang said that reaching flowering stage in three weeks didn't mean that the carbohydrate reserves were replenished.
"Some stands with high harvest frequency were put under too much stress during the season such that in fall (likely including a fall cutting) they could not sufficiently replenish carbohydrate reserves to make it through the long winter," Lang said.
Al Wessels of Crop Production Services in Dyersville said winter-kill is widespread in his area.
"Some are replanting, some are moving what they hoped to keep and putting in corn and more new seeding," Wessels said. "Some are interseeding Italian rye grass. People are concerned about being short on forage."
Lang received calls from Dubuque, Delaware, Allamakee, Winnshiek and Chickasaw counties.
If producers haven't done so already, they need to evaluate stands, Lang said. Fields have greened up enough to tell the good from the bad.
Steve Barnhart, ISU Extension forage specialist, posted information on stand evaluation of alfalfa and other forages in the Integrated Crop Management News at: http://www.extension.iastate.edu/CropNews/2013/0318barnhart.htm.
An alternative evaluation method is to use stem counts, Lang said. Once alfalfa plants reach 6 to 8 inches tall, count stems per square foot for a better estimate of stand potential. A University of Wisconsin publication explains the stem count method at: http://learningstore.uwex.edu/assets/pdfs/A3620.pdf
"To summarize, alfalfa stands averaging 55 or more stems per square foot are excellent stands," Lang said.
Joel DeJong, ISU Extension field agronomist in LeMars in northwest Iowa, said that in his area there has been a little thinning of older stands, but most seem to be recovering pretty well.
Dan Undersander, University of Wisconsin Extension forage agronomist, wrote that there have been reports of significant stand damage across Wisconsin and southern Minnesota ranging from low spots in fields to significant portions of fields.
Lang offers the following options to deal with injured alfalfa stands:
• New seedings of alfalfa can be interseeded with perennial forages including alfalfa. Autoxicity with alfalfa is a minimal concern within the first year of establishment.
• Start over with a new seeding again. Autotoxicity is a minimal concern within the first year of establishment.
• Older stands could be interseeded with Italian rye grass in an attempt to boost yield in this last year of production for that stand. Most of the yield contribution will be with 3rd and 4th crop.
• Rotate failed new seeding or older stand to corn silage.
• Keep a somewhat questionable stand for first crop harvest, and then rotate to a shorter season corn silage hybrid.