– Mark Sulc, OSU Extension Forage Specialist
In the September 6, 2005 issue of the CORN newsletter I wrote about the risks of fall cutting alfalfa, and how to minimize that risk. With the temperatures and good moisture this fall, alfalfa has grown exceptionally well. I have received many questions as to whether this amount of growth going into the winter can harm the stand. The fear is that the alfalfa will smother itself out this winter.
The excessive alfalfa growth will NOT harm the stand. I have let stands of alfalfa go into the winter with as much growth as we see this fall, and I have never experienced a problem or seen the crop “smother out”.
Think about this: 75-80% of the alfalfa crop this time of year is water. In other words, the dry matter content is around 20-25%. So divide what you see out there by 4, and that will be how much residue remains after a couple of hard frosts. There will be much less residue left than it appears right now.
Perhaps if it were to snow early on warm soils covered with lush alfalfa, and the snow were to stay there all winter long, we just might see some snow mold on the alfalfa. But that would be a very rare occasion in Ohio, with the exception of the lakeside snowbelt. In southern Ohio, its possible that alfalfa weevils could lay eggs in the alfalfa stand, potentially increasing weevil populations early next spring. That could happen even with a lot less growth, and other factors influence weevil populations in the spring.
There really is no need to take a cutting now in order to remove the large amount of alfalfa growth. In fact, considering all factors, cutting this week probably holds more risk to the stand than not cutting. If we cut this week, we are likely to have enough good growing weather left for the alfalfa to regrow over the next 2-3 weeks. Regrowth will burn up precious root reserves that are needed for the winter and early spring. There won’t be enough time to replenish those root reserves if the alfalfa is cut now.
If the forage is really needed, a LATE fall harvest can be considered, IF the soil is well drained. By LATE, I mean as close as possible to a killing frost of alfalfa, which is 25 F for several hours. This often does not happen until sometime in November in Ohio. I know that the weather is usually lousy in November for cutting forage, but waiting another 2 weeks to get closer to the killing frost will prevent regrowth and loss of energy reserves, and will reduce the risk of less vigorous stands next spring.
A late fall harvest should only be considered if the soil is well drained and there is no history or risk of heaving on that particular soil. Without residue cover, the temperature of the soil will fluctuate much more and heaving is more likely. This happened in a study at Wooster, when a November 1 cutting resulted in heaving of up to 50% of the plants. Where no fall cutting was made, less than 10% of the plants heaved.
Fall management of alfalfa is one of the few controllable factors that will potentially influence the health of your alfalfa stand next spring. If you don’t need the forage, walk away from it and let it insulate your stand this winter. It won’t smother out because of excessive alfalfa growth.
If you need the forage, then take a cutting the last week of October or early November, and only on well-drained soils. Also leave a 6-inch stubble. If you do cut this fall, leave some strips or areas that you do not cut within the same field. You might learn something interesting next spring about fall cutting on your farm by having those side-by-side comparisons