Im going over last yrs. fert. program. At the beginning of the dryer part of the season AND towards the end of fall I noticed some lawns looked less than ave. as far as color goes. Im going to add iron to my program. Should I add it in the early summer, late fall, or both? Im trying to keep the turf lush and green as long as I can. Already I have 2 pre-emergent aps, 2 post- emergents, fall fert., and lime. Thanks for your input.