Here's the link for more info:
http://www.agr.state.nc.us/agronomi/sthome.htm

They have sample boxes there you can pick up and fill with dirt. Make
sure you note exactly where you got the sample, both on the box and in a
note to yourself, before you bring them in for testing. Otherwise it's
easy to forget exactly where a sample came from. There are also master
gardeners on staff there who can answer just about any gardening question.

MAC