Do the home soil tests work very well or do you know of a mail company that is cheap?
Soil testing -
For basic testing, most of the Sudbury soil kits are satisfactory for determining pH, N, P, and K levels. For anything else, your University Extension service or your Agricultural Extension can provide very thorough testing of your soil. If you need the results quickly, and your testing needs are basic, the homeowner kits by Sudbury or LaMotte will serve you well.
If you are looking to do more precise testing, LaMotte sells some fairly reasonable pricing on soil test kits with a rather wide variety of testing protocols.
The best testing kits available to the homeowner are Hach kits, but they are prohibitively expensive.