Many producers like the option of gaining additional forages by harvesting a fall crop of alfalfa. However, use caution when completing this practice. When done at the incorrect time, fall harvest can increase the chance of winter kill by interfering with accumulation of root reserves and decrease next season’s production.
Therefore, you should weigh the risk of damaging your alfalfa stand against your need for additional forages. For the best time to conduct a fall harvest in your area, contact your local extension agent or agronomist.
In general, the risk to alfalfa stand life increases with increased stand age, risk also increases with increased number of cuts per season. Recent research, however, indicates that the length of the harvest interval prior to fall cutting is more important than the date of fall cutting for reducing the overall risk to an alfalfa stand. This means a rest period of at least 6 weeks is advisable between the last two cuts of the season. Risk also is reduced if fall cutting is not followed by an unusually early spring harvest.
A late fall harvest can also be completed after a killing frost (25o F for several hours.) Caution: removing topgrowth at this time can dramatically increase the risk of legume frost heaving on heavy soils. A method of correcting this would be to apply 4 tons/acre of strawy manure or 2 tons/acre of old hay or straw to reduce the frost heaving potential.
Avoid fall harvest of new seeding, and select fields that are well drained and have optimal soil pH and fertility. These fields will stand the best chance of avoiding injury when taking a fall harvest.
There are factors we cannot control that affect persistence of fall-cut alfalfa, such as temperature and temperature fluctuations throughout the winter, and precipitation through the fall and winter. Also at this point in the season we no longer have control over many of the "controllable" factors affecting persistence of fall-cut alfalfa. These include variety, soil pH and soil drainage. For alfalfa and alfalfa-grass stands, fall harvest priorities should be:
- Alfalfa stands that are likely to be rotated to another crop in 2017.
- Fields with the longest interval since the previous cut.
- Alfalfa stands in their 1st or 2nd year.
- Established alfalfa stands in their 3rd year or older.