Hello crankey1
Bone ash and bone meal are excellent soil ammendments for sources of phosphorous. The problem is, they need to be mixed well into the soil, and require a bit of time to be broken down to a form easily available to the roots. If you have only six weeks to go, it may not be long enough for optimum results.
To use it at this point, spread about one tablespoon per gallon of soil on the surface, and rake it in as best you can with a fork. Don't tear too many of the surface roots.... just try to get it mixed in well.
For immediately available organic P, look into bat guano.