This Issue . . .
Harvesting Alfalfa - Frequently Asked Questions
That Improve Winter Survival in Alfalfa
Tips for Seeding Alfalfa
Is there a critical fall
period when alfalfa should not be harvested?
Alfalfa should not be cut 4-6 weeks before the first killing frost (about
days, cooler temperatures, and drier soils trigger the plant to slow
growth and begin storing root reserves for the winter and growth the
following spring. If alfalfa is cut during this period and begins to
regrow it will need to use root reserves. If a killing frost occurs before
root reserves are restored (10” or bud stage), then the plant may not
have enough reserves for the winter and spring regrowth.
Will I injure my newly
established stand if I cut it now? Wouldn’t it be better to cut the
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
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
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
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
What other factors affect
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.
Johns, Ag-Info Centre, Alberta Agriculture Food & Rural Development
and John,VanDyk, Iowa State
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
· 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
facts you need to know to establish a good stand.
· Plant on well drained soils. If you have it, brown to
brownish red soils are good signs you are on the right track.
Hard-pan (soggy) soils are no place for alfalfa!
· The soil pH must be 6.5 or above at seeding.
A lower pH soil test just ahead of intended seeding needs to be
treated for next year’s seeding plans: (to amend a low pH
takes 6-12 months).
· Elevate P and K according to current soil test recommendations.
· Do not bury the seed. Usually 1/4 to 1/2 inch depth is about right.
Can be a little deeper in sandy soils.
· A firm seedbed helps to locate the seed at the right depth and
holds moisture for uniform, early plant growth. (You can’t
beat a cultipacker before and after seeding.)
· Seeding time: Spring: As soon as the frost is out of the ground.
At least 6 weeks ahead of historical freeze.
· Seeding rate: 15-20 pound range nationwide, but generally
20% higher in South and far West.
· Variety selection: Alfagraze, AmeriGraze 401 +Z, AmeriGraze 701,
· Seeding with companion (nurse) crop? Only when erosion hazard is
great without it and if you feel you are unable to control early
weeds. Remove companion crop as early as possible for
hay or silage. Don’t damage alfalfa in the process!
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