If you are looking for acceptable values for crops in your area, you should check out what publications your state Department of Ag or Land Grant College have put out. These are generally a pretty good guide to what soil tests you should be using, and what nutrients you need at various soil test levels.

If you are looking to understand what goes into a fertilizer recommendation, and what the various nutrients do in the soil and in your crops, check out the Soil Fertility Handbook:

http://www.omafra.gov.on.ca/english/crops/pub611/p611order.htm

 It was written to pull together a bunch of useful information for farmers and agronomists between two covers, that is normally spread over several textbooks.  The examples are from Ontario, and so most familiar to anyone in the eastern Corn Belt, but the principles apply across North America.  I wrote much of it, and edited the rest, so I know it's right!

 Keith