drobin-
I like to add a little quick release with iron at the very tail end of the season (as in right now). To further expound, I like to fert with a little higher k-p in the early fall so as to encourage good strong root growth in the Sept, Oct and November months. One reason I like to add a little extra n in the late fall is to help neutralize the added carbon content from the mulched up/ ground up leaves.
This thread may help you:
http://www.lawnsite.com/showthread.p...zer+fertilizer