Late Season Alfalfa Harvest
Alfalfa must have some fall regrowth after the last cutting to produce and store carbohydrates and nitrogen in the root crown to help assure winter stand survival and initiate new growth with vigor in the spring (Figure 1). When to harvest the last cutting is always somewhat in question. Generally mid-September is the historical last time to cut alfalfa in northern Kansas (about 40-degree N latitude). This can allow for substantial regrowth before a killing frost that usually occurs in mid to late October in northern Kansas. Occasionally, producers harvest alfalfa after that killing frost, which does not impact survivability of the crop. Another way to determine the last cutting window is to use growing degree days (GDD). To maximize survivability potential, alfalfa should accumulate at least 500 GDD (at a base of 41 °F) before winter.
Grazing alfalfa after a killing frost is also an option to take advantage of available forage late in the year. A killing frost for alfalfa occurs when temperatures reach about 24° F for at least an hour. In southern latitudes, frost generally occurs later in the fall and the last cutting also occurs later.
If dry weather was present from late July into August, alfalfa growth usually stops and results in lower tonnage for the last cutting. If September is cooler and wetter, which favors forage growth, a late-September cutting should produce higher tonnage. However, in that case the producer is assuming the first frost date will occur on or later than the average date. Every year the last alfalfa cutting is a decision between forage yield and regrowth potential to help insure a healthy stand next spring.
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields. Channel® and the Arrow Design® and Seedsmanship At Work® are registered trademarks of Channel Bio, LLC. All other trademarks are the property of their respective owners. ©2021 Bayer Group. All rights reserved.