Callaway County
Callaway County
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Jarman's Weekly Agronomy News February 2, 2000 |
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Alfalfa Dormancy Period Affects Winter Survival and Yield |
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Missouri alfalfa growers can be more daring in their selection of new varieties. Variety selection has probably been too conservative on the side of early dormancy. Dormancy is a balancing act. Growers want a variety that goes dormant early enough to survive Missouri winters, but also want a variety that continues growing in the fall and starts growing early in the spring. Typically, alfalfa slows the growth of leaves and stems in the fall and starts storing carbohydrates in the roots. That stored energy helps the plant survive the winter. And, the reserve gives the plant a jump-start the next spring. However, if a plant goes dormant too early, forage production is lost. If it goes dormant too late, the plant might winterkill. The goal is to find a happy medium between production and persistence. In the MU variety trials, Rob Kallenbach - UMC Forage Specialist, rates alfalfa plants on their height in inches in October. This is an indicator of the dormancy group for a new variety. Varieties with known dormancy periods are planted in the test plots for comparison. Producers in southern Missouri should look at dormancy groups 4 and 5. Alfalfa growers in northern Missouri will pick from groups 3 and 4. The lower numbered groups are for colder northern climates. The high numbers, which go up to 10, are for hotter regions. Unfortunately, the list of alfalfa varieties with their fall dormancy ratings is much too long for this article. There are approximately 170 varieties in the dormancy groups 3 and 4. This list also has an evaluation of each variety's disease and insect resistance. Producers should select variety dormancy groups certified by the Alfalfa Council. Producers can obtain that list from the council at 10920 Ambassador Drive, No. 302, Kansas City, MO 64153 or via the Internet at the web address listed at the end of this article. Dormancy is affected by day length. As days grow shorter, plants begin to shut down the aboveground growth. A problem in Missouri is when alfalfa breaks dormancy too early. A warm spell in February can cause the plants that are too non-dormant to start growing. Then, invariably, a late-season cold snap freezes the plants. The challenge is to achieve a balance between early production and persistence. Variety test results have been compiled at three locations in the state: the MU Southwest Research Center, Mount Vernon, Mo.; the MU farm at Columbia, Mo.; and the Forage System Research Center, Linneus, Mo. Alfalfa producers are recommended to look at results from the nearest test plots. The results are available at University Extension Center located in each county or on the MU web at http://agebb.missouri.edu/. The Alfalfa Council's website for dormancy ratings and pest resistance is at: http://www.alfalfa.org/falldormancy.html The source for this article is Rob Kallenbach, Assistant Extension Professor of Agronomy and State Forage Specialist, University of Missouri - Columbia, (573) 882-2002 Private Pesticide Applicators Training (PPAT) will be held at the Callaway County Extension Center on February 7, 2000 from 7:00 to 9:00 p.m. Producers of agricultural products needing certification to purchase and apply Restricted Use Pesticides (RUP) need to attend this class.
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