With strong hay prices today and a need to replace some of our stands of alfalfa, I often get asked how quickly can I re-seed an alfalfa field back into alfalfa. The problem that we face is Alfalfa Autotoxicity that remains after an alfalfa plant is killed. Best option to bypass any trouble with Autotoxicity is to rotate to another crop and wait a minimum of one year to go back to alfalfa.