Linda wrote:
I know some swear by chook poo, some seasol,
personally I can't find anything better than blood and bone.

Linda (Perth)

The question has no answer because there is no such thing as the "best" soil
amendment under all circumstances. The best one for a given situation is
the one that does what is needed for that soil at that time for that crop
and is readily available and cheap. At various times I have used: chicken
litter, horse and cow manure, compost, garden lime, dolomite, gypsum,
potassium sulphate, seasol, trace element mix, blood and bone and probably a
few more that I have forgotten.

David