This is all very interesting and entertaining but I had to go back to the top to find out what the original purpose of the tread is....
My two cents worth:
I am also wondering about the health of the soil in a galvanized stock tank? Jury is still out. I suppose if the interior were sealed or lined to prevent leaching I might be more comfortable with the idea.
The soil where I live (south Georgia) is basically sand covered in oily stuff that leaked out of cars for several generations so I only garden in raised beds and containers; never in the native soil. I make my own soil mix and yes, sometimes add mushroom compost although I buy it in a bag retail so it's not the freshest.
The mixture I use is basically composted manure, sand, pine fines, my home made compost and a few handfuls of limestone. More limestone for the cole crops. If I come across some peat moss, coir, mushroom compost, perlite, vermiculite it gets added to the mix in no particular proportions.
