Ok - I just tested my soil. My pH is around 6.5-7.5, my N is non
existant, P and K are good. I live in central FL, my back yard is
primarily sand.

According to this web site:

http://edis.ifas.ufl.edu/LH012

The best soil amendment to use would be colloidal phosphate - except no
one around here seems to know what the heck it is! I can't find it
anywhere....

I'd like to prep my soil so that I can sow some Bahia grass seeds this
spring, but don't know what to do....

Anyone?