By Scout Nelson
As the growing season comes to an end, farmers need to decide whether to take another alfalfa cutting, when to harvest, and how long their stands can remain productive. These decisions affect the crop's ability to survive winter and grow well the following spring. Proper fall management helps protect alfalfa plants, maintain forage production, and extend the life of healthy stands.
Parker Witt, SDSU Extension Crop-Livestock Systems Field Specialist, highlighted the importance of planning the final alfalfa harvest around plant growth, stored energy, and local weather conditions. Giving alfalfa enough time to prepare for winter is a key step in maintaining strong stands and supporting future forage production.
Why Alfalfa Needs Time to Rest?
Alfalfa is a perennial crop, which means it can grow for several years. To survive winter and produce new growth in spring, the plant stores carbohydrates, or energy reserves, in its roots and crown. These reserves help the plant grow after winter dormancy.
When farmers cut alfalfa, the plant uses stored energy to produce new leaves. As the leaves grow, they begin making food through photosynthesis and help rebuild the plant's energy reserves. This process usually becomes more effective when regrowth reaches about 7 to 10 inches.
If alfalfa is cut too often or does not have enough time to recover, its energy reserves may become too low. This can weaken the plants, reduce future production, and increase the risk of winter damage.
The Importance of Winterization
Winterization is the process through which alfalfa prepares for cold weather by rebuilding its energy reserves and becoming ready for dormancy. Young and healthy stands, especially those less than four years old, need enough time to complete this process before a killing frost.
On average, alfalfa needs about 500 growing degree days without interruption to complete winterization. This generally means allowing five to six weeks between the final cutting and the first killing frost.
A killing frost occurs when temperatures remain at 25°F or lower for more than four hours. Weaker alfalfa stands may need an even longer recovery period before winter arrives.
Cutting during the winterization period can place extra stress on plants. A light frost may not stop growth completely, and alfalfa may continue to regrow when temperatures rise. Harvesting during this time can reduce stored energy and increase the risk of winterkill.
When Should Farmers Make the Final Cutting
In South Dakota, the first true killing frost typically occurs during the first half of October. In a normal year, this means farmers should plan their final regular cutting no later than the first week of September.
However, weather patterns vary from year to year, so farmers should consider local forecasts and field conditions when making harvest decisions.
An exception applies to stands scheduled for removal and crop rotation the following season. These stands may be harvested later because they are not expected to remain in production for another year.
Farmers can also consider a final harvest at the end of the winterization period, around the time of a true killing frost. This approach allows the plants to rebuild their energy reserves before harvest and helps capture additional forage without cutting during the recovery period.
However, timing remains important. If warm weather follows the frost, alfalfa may begin growing again. Farmers should watch weather forecasts and make sure cold conditions continue after the final harvest.
Managing Alfalfa Used for Grazing
Farmers who use alfalfa as pasture need to take extra care after frost. Frost-damaged alfalfa can increase the risk of bloat in cattle.
To lower this risk, allow at least 10 days after a killing frost before grazing the crop. This waiting period helps the damaged plants dry down and reduces the danger to livestock. Farmers should also consider field conditions and seek local guidance when needed.
Protecting Plants Through Winter
Regardless of the harvest method, leaving five to six inches of stubble after cutting is important. Standing stubble helps reduce soil erosion, traps snow and provides some protection for the plant's crown and roots against very cold winter temperatures.
These simple steps can improve winter protection and help maintain the long-term health of alfalfa stands.
Building Productive Alfalfa Stands
Good end-of-season management depends on understanding plant growth, watching weather conditions, and allowing enough time for winter preparation. Avoiding risky fall cuttings, choosing suitable harvest dates, and leaving enough stubble can help farmers protect their investment.
With proper care, alfalfa stands can remain productive for several years in South Dakota. Farmers can find more guidance on forage production and crop management through the SDSU Extension forage page.
Photo Credit: gettyimages-fuzzmartin
Categories: South Dakota, Crops, Hay & Forage, Weather