With links to those available online.

Free online text, from USDA.

“This application retrieves graphical summaries of soil types associated with the iPhone's current geographic location, based on a user defined horizontal precision. Sketches of soil profiles are linked to their official soil series description (OSD) page.”

USDA’s soil survey handbook and manual, soil change guide, soil taxonomy, etc.

Has “soil maps and data . . . for more than 95 percent of the nation’s counties. “ Includes interactive maps and soil characterization data.