I like AMS rather than urea for N. Soils and pastures around here really respond to some S.

Fertilizing with N and S around the first of June seems to work better than N earlier for me in some pastures not up to speed. We get a good first flush of growth anyway in the spring, almost to excess and more than I can graze and difficult to dry for hay. AMS around Memorial Day brings on a second and third flush of growth.