Rice is the single, most important crop and staple grain of Bangladesh. The combination of rising population and increased food demand has placed tremendous pressure on the soil resource in Bangladesh. Floodplain soils are dominated by micas and their degradation products, including Fe-rich vermiculite and smectite, and are generally regarded as high in K. In spite of the Fe-rich and K-rich layer silicate mineralogy; widespread K-deficiency in the rice paddy soils is increasing throughout Bangladesh. Removal of straw from the field and its use as cattle feed and fuel exacerbates the removal of nutrients including K, and the intensification of cropping systems with unbalanced fertilizer application has resulted in depletion of “readily available” K in large areas of Bangladesh soils. Rice paddy soils from five districts of Bangladesh were sampled and studied to determine physical, chemical and mineralogical properties, and to investigate the ability of the soils to release or fix K under varying redox conditions.