This service is distinct from the USDA Economics and Statistics System at Cornell University. Besides reading about the mission and organization of the service (including email addresses), you can also read their catalog of publications. You can retrieve their data (much of it from the Cornell site). However, they also offer "U.S. State Fact Sheets" and "U.S. County Economic Types" which offer extensive information on agriculture by counties and states.
http://www.econ.ag.gov/