While this page is mainly for Missouri, the process can certainly apply to any state – just do a search for “Soil Test and the name of your state.” I’d recommend yearly testing until your soil tests good.
– Find and Extension close to you. This is the St. Louis area office site.
– Follow the process in the graphic below – the cost is $20.
– Basic Information – Soil Testing and Plant Diagnostic Services
– Interpreting Missouri Soil Test Reports http://extension.missouri.edu/p/G9112
– Soil and Nutrient Article – http://extension.missouri.edu/p/MG4