Do “Typical” Pedons Change with 50 Years of Low Intensity Land Use?.

Classical pedologic theory postulates that soil formation occurs on geologic time scales.  It further suggests that most human impacts are largely limited to upper portion of the solum.   National Cooperative Soil Survey best practices recommends “representative pedons” should be collected from locations having minimal human impacts.  The purpose  of this study is to link these two ideas by testing whether whole profiles evolve in response to human uses, especially crop production.   Our approach was to sample and analyze pedons originally sampled as part of the  National Cooperative Soil Survey program.  Our sampling area is the state of Iowa.  Our sampling unit was the pedon.   Our findings include decreases in soil surface pH and carbon content, deeper depths to carbonates and decreased total depth of granular structure in surface horizons.   On average, depth of 3/3 Munsell colors has not changed, but certain landscape positions show significant increases or decreases in depth of 3/3 colors.  The integration of these findings will likely yield changes in soil taxonomy and classification, as well as have implications for future land use.