If your spring seeding plans include alfalfa following alfalfa, proceed with caution.
Trials at several universities have shown that autoxicity can hurt yield and stand life when alfalfa replaces alfalfa on the same ground.
For best results, say researchers, seed alfalfa following another crop. If that’s not possible, kill the old stand with tillage or a herbicide, then wait as long as possible before reseeding.
Some work has shown that two weeks between stands may be enough. But University of Kentucky agronomist Monroe Rasnake suggests that, as a minimum, growers should kill the old stand in spring and reseed in fall, or vice versa. And University of Wisconsin scientists got better stands with fall killing-spring reseeding than with spring killing and replanting.
Other factors:
o Autotoxicity is less troublesome on sandy soils than on heavier ones, so less time is needed between stands.
o Tillage dilutes autotoxic compounds, so a longer waiting period is needed in no-till situations.
o Some varieties are more susceptible to the problem than others. V