Aha very interesting was your intention also to fix phosphorus?too much bentonite is no good, i wouldn't go over 2% of soil mix, and make sure it's finely crushed.
i collected a bunch from a naturally occuring bentonite area leased by BLM. 2$ for 2 cu yds, had to collect it myself, but the price was right.
i used fabric pots outside, greased the insides of the fabric pots before filling with soil. at harvest time the roots had filed the bentonite area densely because the bentonite held so much water. plants did well, no ill effects.
i read someplace that the calcium bentonite is the best to use, was unable to find out WHAT kind i used.
Aha very interesting was your intention also to fix phosphorus?
Red lake earth brand makes a food grade bentonite + DE mix from the animal feed store around here.
Seems NAPA stores are switching from DE and now selling Montmorillonite clay for drysweep.
Pretty sure microbe man said he uses sodium bentonite.