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Last Alfalfa Harvest for the Season

Question

Tradition has it that we should take the last cutting of alfalfa around September 15, which would allow regrowth and time for storage of carbohydrate and nitrogen in the crown for overwintering and spring green-up.  Realistically our long-term average first freeze is around October 10, and the first alfalfa killing freeze, 23-25 degrees, is around October 20.  In recent years that has been all over the map though.

I have a 2007 fall seeding which was cut 3 times, early June, mid July and mid August.  On September 15 it only had about 8-10 inches of re-growth.  So I elected not to cut it.  We have had great growing conditions since and it currently is probably 14 inches tall. I started reading on the internet about fall cutting strategies, and found that the thoughts of many extension specialists seem to have changed.  That since the plant responds to decreasing day length in late summer by slowing growth and storing photosynthate, a better harvest strategy to reduce stand loss is to delay the last cutting from mid-September to late October (either after a killing freeze or late enough to prevent significant regrowth).  A research agronomist had a paper from work in the mid 90's showing no real stand reduction, but some slight yield reduction in the 1st cutting the next spring following that system.  So my question is did I understand that correctly, that taking a last scheduled cutting in early September followed by an "opportunity cutting" in late October would be preferred to a scheduled late September/early October last cutting?  Out here a lot of late August-early September 4th cuttings are pretty small, but we get some additional growth in Late September and October when it cools off.  We also have a little better hay making opportunities, especially put up in big round bales.  There is a lot of alfalfa down right now.  In this area we don't have a lot of disease problems so stands should last 5-6 years or more if fertilized and managed properly. But I suspect the routine late September-early October harvest may be reducing stand longevity.

I would appreciate your thoughts.

Answer

The question of harvest schedule is appropriate. The result of harvesting at a less than ideal time can be different based upon stresses (examples: spring freeze, competition from weeds, fertility, insect, disease, too rigorous cutting schedule, cold winter with no snowfall, winter temperatures fluctuating wildly) the crop has experienced preceding and following the "less than ideal" harvest timing. Variety selection makes a difference, too.

Your statement "taking a last scheduled cutting in early September followed by an "opportunity cutting" in late October would be preferred to a scheduled late September/early October last cutting" is a good principle to follow, although the most conservative approach is to not harvest in the fall at all.
If an after alfalfa is dormant harvest occurs, realize that making hay is difficult and harvesting the crop as silage (traditional or as baleage)is less risky. If there is a cool-season grass growing with the alfalfa, some folks are electing to graze the residual growth if fencing exists and soil conditions permit harvest by critter.
Some strategies include leaving a high stubble to reduce the chance of ice "hugging" alfalfa crowns.

Risk management needs to be thought about.
Examples: If 2008 is truly the last year for the alfalfa, growth is excellent today, the value as a forage exceeds the lost value of N for the crop that follows in 2009, and weather is super . . .harvest!

If it is year two or three for the alfalfa, crop vigor is wonderful today and weather is to be great for a week, but the potential loss of the ill-timed harvested alfalfa means that my financial status will be impaired, keep the mower-conditioner in the shed.

 

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Keith Johnson
Professor of Agronomy and Forage Crops Specialist
1150 Lilly Hall of Life Sciences
West Lafayette, IN 47907-1150
phone: 765-494-4800
fax: 765-496-2926
e-mail:johnsonk@purdue.edu

 

 

For more forage information contact Dr. Keith Johnson: johnsonk@purdue.edu

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