The 2012 drought reduced alfalfa yield by significantly across Wisconsin. It appears, that while some regions (especially northeast Wisconsin) had better yield than others, the overall average yield was down about 25% and (since haylage is made first and the rest baled) hay production may be down by as much as 50%.
In the Southern part of the Wisconsin yield of first cutting was reduced due to a dry March. Alfalfa root systems die back to some extent over winter. The root system requires good soil moisture in the early spring to regrow. If a strong root system forms then high yields will occur on first cutting. If the root system growth is restricted by dry soil, then the top growth will be reduced, even if good rain occurs in the later part of the first cutting growth period (during April and May) as occurred this past year.