Many claim alfalfa pellets are good in that they stimulate root development. I'm not sure the NPK breakdown, though.

mulch mow and mulch all the leaves you can find. you will get phosphorous from the clippings.

First of all, which test did you get? The fact that you're asking about organic stuff and pretty much almost all tests are for synthetic program, not organic. Two entirely different concept.

Where are you located? The United States zone 7 covers too braod an area to try to answer the question with any intelligence, aside from asking the obvious question, "how do you know your soil is low in Phosphorus?"

alfalfa meal

Epson Slats, just mix some into your bag of fertilizer and feed as normal.