We attempted to determine if the clay mineralogy class of fine-textured soils in New York State could be reliably predicted using a total potassium (K2O) determination. Previous x-ray diffraction results have shown that the fine-textured soils in New York State are in the illitic clay mineralogy class, except for those found in the St. Lawrence Valley, which have a mixed clay mineralogy class. The total potassium method did correctly predict hydrous mica content and clay mineralogy of seven pedons that represented the lowland regions of New York State excluding the St. Lawrence Valley. Five pedons from the St. Lawrence Valley could not be correctly predicted due to the presence of significant quantities of K feldspars and inter stratified (2:1) minerals in the clay fraction. For the other lowland regions in New York State, the total potassium method does provide a sufficiently reliable method for predicting hydrous mica content and clay mineralogy class for soil series that are currently being surveyed and correlated.
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