Patching in or thickening up winter-injured alfalfa stands with more alfalfa seed is not always successful. Existing alfalfa disease pressure and the likelihood of the presence of toxins from the old alfalfa plants on the site may severely restrict the success of a new seeding effort immediately in the same field. We have a lot to learn about the conditions that make this practice successful. Currently, there are only a few guidelines we can offer.
- It is best to rotate the new seeding to another field and wait a year or more before reseeding alfalfa back into the old field.
- Red clover often can be seeded successfully into an old, or injured alfalfa field to extend the productivity for a year or two longer.
- If you attempt to "thicken" a thin, old alfalfa stand with interseeding or broadcast seeding of new seed, you may get some new alfalfa plants to establish, but you will never recreate a uniformly thick stand with these attempts.
- Forage agronomists and researchers disagree on the likelihood of success of reseeding a failed new seeding, or reseeding a winter-injured stand following tillage or herbicide destruction. Some researchers suggest that you can reseed successfully after as little as two weeks following destruction of the old stand; others feel there is a good chance of success within the first 12 to 15 months of the original seeding. These efforts should be considered a risk.
- If you attempt to seed more alfalfa into the injured old stand, consider that the new seedlings may be stressed if placed immediately under the harvest schedule of the existing older plants. Best management would be to allow the newly seeded plants to reach first flower before harvest of the field.
This article originally appeared on page 46 of the IC-478 (6) -- April 28, 1997 issue.