Ironite! Does it work?!?! : lawncare - reddit
A cheaper and better solution (pun intended) is applying 4 oz Ferrous sulfate and 3.4 oz ammonium sulfate per gallon per 1000 sq ft. You can get the ferrous sulfate from kelp4less and the ammonium sulfate from a local big box or farm supply. It might me marketed as 21-0-0. You will be applying a foliar spray and the grass will turn greener quicker.