Potassium availability to plants was estimated at a Fragiaqualf-Fragiudalf catena in southern Indiana. Plant-available nonexchangeable potassium (PANK = nonexchangeable K estimated with NaBPh4 extraction - (minus) exchangeable K estimated from mehlich 3 extraction) was estimated for 128 georeferenced sample points and three depths. K release over time with NaBPh4 extraction was analyzed. Ratios between quick release (<24 hours) and slow release (>24 hours) were higher at better drained sites. PANK, NaBPh4 K, and mehlich K were all higher at the better drained locations. Reasons for the difference may be higher fixation of K by soil clays at the more-weathered wetter sites, movement of K with soil moisture, or slower weathering of clay from the K-rich micaceous minerals at the less-weathered better-drained sites. Clay mineralogy was analyzed with x-ray diffraction in order to answer whether mineralogy or movement answers the question. K concentrations and other soil properties were modeled with geostatistical tools to provide visualizations of K movement/concentration.