I'm no soil biologist but I will say this. There has been a Phosphorus ban in NW Arkansas the last 4-5 yrs ( Huge Lawsuit brought about the ban) This has made professional quality blends that include P very difficult to come by especially at a reasonable price. I am using a blend this year that has 3% P. My lawns look better than they have in yrs. Levels of N and K are about the same as they have always been. Just a personal observation....
"The Poor Fish" circa 1930's: The Poor Fish wouldn't have been caught if he'd known enough to keep his fool mouth shut.
"Opportunity is missed by most because it is dressed in overalls and looks like work"- Thomas Edison, businessman/inventor