Yes it is. Because I am spraying iron 12 months out of the year, my D30 is overhauled every Christmas. My MS074 is also torn down and rebuilt every Christmas as well. Applying a certain total amount of iron sulfate positively affects pH. That and the mix to apply it contains 5 lb food grade citric acid. In my alkaline tap water, iron sulfate turns into red sludge. Water pH is 8. I have noticed the same hardening effect on my warm season grasses that the British do. Right now, I am working on the oldest British lawn bowling green in Hawaii. I need to feed the grass, get it green without creating a lot of surge growth and keeping the surface fast. Not a problem for me. Iron sulfate, potassium nitrate, and a little ammonium sulfate. Not much different from what I spray on my residential lawns. In my eyes, I have done wrong if my spray causes the grass to grow 6" per week. Keep in mind, if I am not the one mowing it, it is being mowed by someone else with a reel mower at 3/8" twice a month not every week.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738