In oPYrb.165236$HS4.1342989@attbi_s01 Centifolia wrote:
If applied to the surface it will stay there chemically
bound to the soil where it is applied.

Well it does move a little, but generally you are right. I mix blood
and bone and Osmocote into the planting soil to address this. I'd be
pretty cautious about putting superphosphate right onto roots.