1) would you put furnace slag in your garden? if you google "slag
chremical composition" the first hit is from our own group and there
are sites linked from there that support the idea of using slag as a
source of micronutrients, specifically Mg, Mn, Fe, and S (there is
also lots of Ca and some K, but given that I already spread wood ash,
those are unneeded)

2) what is the cheapest source of P, per pound of P?