I don't particularly care for some of what George advocates, but he's right on the ortho vs. poly issue. In fact, there is an overwhelming amount of research in support of George.

Here are just a few links:

http://www.uwex.edu/ces/crops/fertsale.htm

http://www.agronomy.ksu.edu/soiltesting/doc1816.ashx

http://fieldcrop.msu.edu/uploads/documents/phosphorus_for_crop_production.pdf

http://www.spectrumanalytic.com/support/library/ff/P_Basics.htm

https://ipni.net/ipniweb/pnt.nsf/5a4b8be72a35cd46852568d9001a18da/7ee68176578798288525740c004b5508!OpenDocument