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.