I'm not sure where this thread has gone, but a few points may need to be considered. 1) P has always been regarded as relatively immobile in the soil. Leaching has never been a worry for water contamination with P. 2) The environmental worry about P applications are off-target apps that put P fertilizers directly in surface water (like getting fert on driveways, sidewalks, roads, and misapplications). Because P is tightly bound to the soil, the only way it can get into water after a proper application is if the soil ends up in the water. 3) K isn't volatile. Urea is volatile. Ester formulations of herbicides are volatile. Gasoline is volatile. K is not. "Volatile" simply means that a compound's vapor pressure is low and it evaporates quickly.