Note that soil topics are interdisciplinary, so some  resources will appear in more than one guide.

Soil as an Agronomic Resource--the first "use" of soil that comes to mind.  These resources focus on how we use soil for farming. (personal copy)

Soil as a Frontier of Knowledge--often taken for granted, soil is actually a frontier of knowledge.  These resources point to the leading edges of soil studies.  (personal copy)

Soil Ecology--the history of soil science has been the story of learning more about what lives in the soil and how we are profoundly effected by that knowledge.  These resources focus on studies of soil biology and ecology.  (personal copy)

USDA Web Soil Survey--how to use US soil survey data to explore social, economic and historical questions.  (personal copy)

If you want a "broad and deep" perspective on the many ways soil is seen from US research and political perspective, see the presentations from a 2016 National Academies of Sciences Engineering Medicine "Soils: The Foundation of Life" workshop.