Thanks gardengal. I have been haunted by the phosphorous myth and have decided to back to square one and take a more scientific approach

What's the phosphorus myth? I'm very curious.

https://www.gardenmyths.com/bloom-booster-fertilizer-nonsense/

I used to be able to get my soil tested at the local university and receive suggestions how I could adjust my soil using approved "organic" ammendments. That was helpful for me.

"https://www.gardenmyths.com/bloom-booster-fertilizer-nonsense/"

That is a completely reasonable and well substantiated premise! Unless previously heavily farmed, very few soils are deficient in P and rarely ever need supplementation. In some areas, phosphorus is a very heavy pollutant, especially when applied in its fertilizer form, and steps have been take to reduce its application. In fact, WA state has now prohibited including P in lawn fertilizer, perhaps the biggest contributor to P overuse and pollution. btw, plants bloom and fruit very productively without so-called "bloom booster" fertilizers. They are really unnecessary and more a marketing gimmick than a defined plant benefit.

And just a FYI but very few land grant universities/extension services offer soil testing these days. Too expensive to staff and maintain the labs. UMass and TAMU are about the only two good ones left.