Phosphorus is quite immobile in soil. Along with natural mineral soil contributions, animals (and humans) tend to poop out a lot of it.

That said, even in very high phosphorus soils, toxicity is very rare. You're more likely to see copper and zinc deficiency symptoms on plants because of the increased plant site competition between phosphorus/copper/zinc rather than any actual phosphorus toxicity issues. This is generally only an issue in high pH soils, though, and it's probably not going to be an issue in Alabama.

My backyard tested very high in P too. Several previous owners had big dogs and I assume the back yard was fenced in for them. I have always wondered it that was the connection.

A common source of high Phosphorus in home gardens is repeated additions of manures.