Hmmmm. Interesting. Down here our suppliers carry Houactinite from the Houston sewage system. It's listed as a 6-3-0 w/1% Iron. Milorganite is 6-2-0 w/4% Fe.
Now I don't live in Houston. I live near Austin.
I used to live in Madison, WI, but not Milwaukee.
So I can't really say whether my crap has 50% more P and 75% less Fe than it did when I lived up North. And yet, it's somehow comforting to know that at age 54, I'm still crappin' out that 6% slow release N.
And the beer farts haven't really changed from the switch from Blatz to Lone Star.