Shortly after that I received a question from Chuck Bowey, wanting to know about seeding alfalfa into grasses. Interseeding alfalfa into alfalfa is almost surely a failed effort.
Competition is the biggest deterrent.
The one caution I did detect was that alfalfa, if managed properly, might out-compete the grass. Haby's early research results showed a reduction of bermudagrass stands after one year when the grass was interseeded with alfalfa in 9-inch rows. Wider row spacings seemed safer, but produced less alfalfa per acre. Haby recommended alfalfa row spacings of 18 to 20 inches to reduce the competition between the alfalfa and grass. Haby has now revised his planting recommendations toward narrower rows when the co-existing species are subjected to grazing.