Plinthite Properties and Implications in Southeastern U.S. Coastal Plain Soils.

Plinthite is commonly found in southeastern U.S. Coastal Plain soils from Virginia to Texas. Greater than 50 soil series classify in plinthic taxa, with many more containing some plinthite.  National Cooperative Soil Survey (NCSS) investigations over the last four decades have led to significant understanding of plinthite and associated soils, but further improvement in its identification, properties, and interpretive effects are needed.  Some of the issues stem from plinthite’s variable degree of cementation, the identification requirement of soil material that irreversibly hardens, its variable morphological forms which differentially affect hydraulic properties, and its complex relationship with contemporary soil formation and saturation.  The goal of this presentation is to briefly summarize our current understanding of plinthite and related soils in this region, and present potential issues that warrant further investigation. We have conducted studies within the Alabama and Georgia Coastal Plain that have evaluated development, hydraulic properties, and hydromorphology of plinthic soils, and these findings will be placed in context of our current understanding. Recent advancements in its definition and quantification (standardized slaking technique) will improve further establishment of pedological relationships. Timely issues including a proposal for a plinthic diagnostic horizon (which exists in the WRB system) and the precedence of plinthite in Soil Taxonomy will also be addressed.