Will I injure my newly established stand if I cut it now? Wouldn’t it be better to cut the older ones?
Actually a newly established stand of alfalfa is less likely to be injured that an older stand (3 years and older). Younger stands are healthier and are free of the crown and root diseases. The available nutrients are also higher in younger stands and improve winter survival. However, if you do harvest a stand during the critical fall period, do not repeat this practice the following year.

For the best survival of the stand, attempt to take last summer cut by late August or very early September, and let regrowth stand in the field (no late cut or grazing). If you have not fertilized in the summer, topdress any needed potassium in late August or early September.

Due to summer harvest delays, my alfalfa is knee-high in mid-September. Can I cut it then?

The answer depends on whether the field will be saved for hay next year. If the answer is "No," harvest anytime. There will only be a slight reduction in nitrogen contribution to the next crop if last top growth is removed. If the answer is "Yes," the field will be kept for hay next year, then determine whether you need the hay from this mid-September harvest. If the answer is "No," leave the last growth in the field--do not graze in fall or winter. If the answer is "Yes," it is best to wait until at or after the killing freeze (23-24°F) in mid-October to cut. Then leave a 5- to 6-inch stubble.

But I can’t get my hay dry in October! What is the risk of cutting in mid-September?

If you cut in mid-September, alfalfa plants will begin to regrow following the mid-September harvest and to use some of their stored carbohydrates; thus, they will have a relatively low level available when the killing freeze comes. Reduced levels of stored carbohydrates can limit winter survival and inhibit regrowth in the spring. With a low level of stored carbohydrates, even a minor premature spring recovery and freeze-back will severely stress the plants.

Can fertility improve winter survival?
Fertility is a very important part of winter survival. Alfalfa can fix nitrogen, but it will still require large amounts of the other nutrients. Potassium (K) helps protect the plant tissues from freezing, plays a role in storing winter reserves, and improves resistance to diseases. Phosphorus (P) will help establish strong root systems and promote vigorous spring growth. The most efficient way to provide these nutrients is at the time of establishment.

What other factors affect winter survival?
Variety, fall moisture conditions, and soil pH will all have a role in winter survival.  Not all alfalfa varieties are the same with regard to winter hardiness.  Remember that rapid growth and yield will usually come at the cost of winter hardiness. 

Soil pH is also important. Alfalfa is best adapted to a soil pH of 6.5. Stands grown in slightly acidic soils (less than 6.0) will be at a greater risk for winter injury and should not be harvested during the critical period.

Wet field conditions in the fall will reduce the amount of dormancy and increase injury from ice sheeting and frost heaving. Dry soils are actually better insulated and hasten the onset of dormancy which will improve winter survival.

Which is the safest way to harvest alfalfa in the fall with out injuring the plant?
The best solution would be to wait until just before or after the killing frost. Alfalfa will be difficult to dry under these conditions so it is advised to ensile it. If you can, leave a 6 in. stubble and some uncut strips to help trap snow. Alternatively, you could try and move up your first cutting date (again you may have to silage it to beat the weather) so that your second cut will fall just before the critical period.

Source:  Mark Johns, Ag-Info Centre, Alberta Agriculture Food & Rural Development and John,VanDyk,  Iowa State University

Factors That Improve

Winter Survival in Alfalfa

· Winter-long snow cover of 4 inches or more

· Winter-tolerant variety

· Two or three summer cut harvest systems with good regrowth between cuttings

· Uninterrupted growth (5 to 6 weeks) during September and October

· All of the last growth of the season left in the field (no cutting or grazing)

· Management of insects (e.g., potato leafhoppers) during the growing season

· Good levels of potassium in the plant

· Young stands or older stands with no root or crown disease

Quick Tips for Seeding Alfalfa

The basic facts you need to know to establish a good stand.