I found this video that has a really good section on having your soil tested.
http://www.24-7agtv.com/Joomla/index.php?option=com_seyret&task=videodirectlink&Itemid=0&id=33
http://www.24-7agtv.com/Joomla/index.php?option=com_seyret&task=videodirectlink&Itemid=0&id=33