Ca-Mg ratios for evaluating pedogenesis in the piedmont province of the southeastern United States of America

The nature of parent materials strongly influences soil development in the southeastern US Piedmont. In this region, most parent materials (saprolite) form from metamorphic and igneous felsic and mafic rocks. Although most soils in felsic terrains are acid and kaolinitic, soils formed from mafic parent materials range from kaolinitic Ultisols to Alfisols with smectite. Because it is sometimes difficult in soils developed in mixed terrains to determine parent material influence, exchangeable Ca/Mg ratios were used to elucidate soil-parent material relationships. Establishment of Ca/Mg signatures diagnostic of soil-parent material suites could facilitate soil mapping activities and forest fertilization regimes. Characterization data collected as part of the National Cooperative Soil Survey (mainly Georgia and Alabama) were evaluated, and soils were grouped by parent material type. The Ca/Mg ratios did not prove to be diagnostic for separating parent materials; however, significant depth trends existed. In m...