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Around the County

Alfalfa and winter damage

April 24, 2009
Wayne Schoper — Brown/Nicollet Extension Educator

This last winter was an old-fashioned winter with lots of cold weather and snow. We have had a slow warm-up and some additional cold days between some warm and sunny ones. Because we do raise a significant amount of alfalfa in this area we have to be concerned with winter hardiness and alfalfa stand longevity. Brown and Nicollet Counties have approximately 15,000 head of dairy cattle and a similar number of beef cattle that consume alfalfa hay and haylage as part of their diet.

Right now, the alfalfa is coming out of dormancy. Alfalfa has the ability to go dormant in the fall and hibernate, if you will, until the warm growing season returns and then resume its growth patterns and produce forage to be consumed by cattle and horses. We raise approximately 20,000 acres of alfalfa in Brown and Nicollet Counties with some of the hay baled dry and some harvested, ensiled and fed as haylage.

So how did we come out of the winter? Time will tell as we need some warm days and temperatures to help the alfalfa green up. Some of the alfalfa was cut too late in the fall, thus not allowing enough time for it to regrow before the winter or perhaps the alfalfa was growing on a south-facing slope which would catch some late winter sunlight that would allow it to break dormancy and then succumb to colder temperatures later on.

Article Photos

One of the most evident results of winter injury is that stands are slow to green-up. If most of the field is starting to grow and you have areas of the field that remain brown or only slightly green, check these areas for injury or death. The best way to diagnose winter injury or winter kill is to dig up random plants (4 to 6 inches deep) and examine their roots. Healthy roots should be firm and white with little evidence of root rot. Winter killed roots become gray and water-soaked initially after soils thaw. Then after the water leaves the root, the tissue becomes brown, dehydrated, and stringy. If the root is soft and water can be easily squeezed from it, or if is brown, dry and stringy; it is likely dead.

It is important to walk your fields and see how your stands of alfalfa survived the winter. Some plants may be damaged but have enough reserves to fuel some early growth before dying. The benchmark is to be able to find at least 5 healthy plants per square foot. For more information about diagnosing and managing winter and frost-damaged alfalfa stands go to www.uwex.edu/ces/crops/uwforage/alfalfa.htm.

Allow injured alfalfa plants to mature longer before cutting. Allowing alfalfa to mature to early or mid bloom before harvesting will help the plants restore needed carbohydrates for subsequent production. How long and during which cutting depends on the extent of winter injury. For severely damaged stands, allow alfalfa to reach nearly full bloom before first cutting, and early flower on subsequent cuttings. This will give these stands the best chance at survival.

If you have a stand of alfalfa with a lot of damage or dead spots, inter-seed these areas with 10-15 lbs/acre with non-heading Italian ryegrass, and plan on terminating these stands after this growing season. Do not seed alfalfa in areas of the alfalfa is dead as there will be residue in the soil from the dead alfalfa that will prevent the newly seeded alfalfa from germinating. Including an additional one-half to three-fouirths bu/acre of oats may improve weed control and boost first cutting yields.

 
 

 

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