“…The recent proposals use ammonium oxalate rather than sodium pyrophosphate to extract the amorphous components. The proposals described by Rourke and Kimble (1989), Kimble (1989), and Rourke (1990) were inadequate for defining spodic horizons, therefore the latest proposal (Rourke, 1991) was developed. The objective of this study was to evaluate the latest proposal (Rourke, 1991) and compare with the chemical criteria of Soil Taxonomy (Soil Survey Staff, 1975) using 39 Michigan pedons with different morphological properties.…”