The difficult alfalfa harvesting conditions in the spring during first cutting causes many farmers to get off schedule for harvesting alfalfa. This raises the question of best management for alfalfa harvest as the end of summer and fall approaches. Farmers have to balance the need for tonnage, forage quality and winter survival, say Michigan State University agronomy experts.
In the late summer and early fall, alfalfa must either be cut early enough so it can re-grow and then replenish root carbohydrates and proteins or so late that the alfalfa does not re-grow less than 8 inches and does not deplete root carbohydrates and proteins.
This has resulted in the recommendation of a ‘no-cut’ window from September to killing frost in states like Michigan.
However, recent research in Quebec, Canada has helped to redefine this window by assuming that if 500 growing degree days (GDD) accumulates after the last cutting there will still be enough re-growth of alfalfa for good carbohydrate accumulation in the crown and roots before a killing frost, and good winter survival and yield the following year.
This means a producer can cut in September as long as there is enough warm weather remaining in the growing season (accumulation of 500 GDD) before a killing frost without hurting the stand. These GDD’s are calculated as the average of the daily minimum and maximum temperatures above 41 degrees F until a killing frost (25 degrees F).
Be sure to check with your local extension office or crop consultant regarding recommendations in your area.
Source: Michigan State University