Timothy - Spring Fertilizing Question

As I've mentioned in earlier posts, we've redone two of our hay fields in timothy.

Spring fertilizing - when do you typically apply? Don't want to go in to early and trample the young grass with the tractor, but also don't want to wait to long such that the first cut hasn't fully benefited from the fertilizer.

Turning warm this week - hopefully more warm than cold days going forward. Things should start greening up quickly.

Any recommendations - rules of thumb are much appreciated as to when you put down you're fertilizer in the spring - especially for timothy.

Thanks!
Bill

Timothy - Spring Fertilizing Question