Hi David,
Thanks for contacting us!  

Texas A&M University provides economical soil testing services and you can find more information at soiltesting.tamu.edu.  

For homeowners you will want to look for the "Urban Soil Submittal Form" which can be found under the "Submittal Forms and Payment Information" link on the right side of the page.

Instructions for taking your sample can be found on the form and ziploc bags work perfectly for mailing your sample to the lab.

Thanks again for contacting us and feel free to email us at <personal data hidden> if you have any additional questions!
Tom & Joe