County Ag News
What is the best cutting management for alfalfa harvest as the end of summer approaches? In order to have good winter survival and rapid greenup for good yield next year, alfalfa must either:
1) be cut early enough in the fall to regrow and replenish root carbohydrates and proteins; or
2) be cut so late that the alfalfa does not regrow or use any root carbohydrates.
This has resulted in the recommendation of a ‘no-cut’ window from Sept. 1 to killing frost for Wisconsin. Research in Quebec has helped define this window by indicating that alfalfa needs 500 growing degree days after the last summer cutting to regrow sufficiently for good winter survival and yield the next year. Thus the date for a final summer cutting is not nearly as important as the temperature and accumulated growing degree days following that cutting.
On the other extreme, we can also cut so late that little regrowth occurs. Cutting when 200 GDD or less will occur indicates that there will be insufficient regrowth to use significant amounts of root carbohydrates. These plants would also have good winter survival.