Different K pools in 197 surface and subsurface soil samples of southern Iran were determined to accurately assess factors affecting K pools distribution. Mineralogical analysis indicated that smectite, mica, chlorite, and palygorskite were the major minerals in the clay fractions. We obtained significant relationships between exchangeable, non-exchangeable, mineral, and total K with mica content, CEC, calcium carbonate equivalent, and clay content. Although many researchers have stated that mineralogical composition determines K status of soils, our studies indicated that some characteristics such as soil moisture and temperature regimes, soil orders, depth, agricultural activity, leaching, and some soil properties like particle size distribution, soil salinity, calcium carbonate equivalent, and cation exchange capacity could also affect K equilibration in the soils. Generally, Histosols and coarsetextured Entisols had the lowest contents of different K pools, and Alfisols and Vertisols had the highest values. On the other hand, soils with xeric moisture and mesic temperature regimes had the highest contents of different K pools. Further research is required to study the relationship between these findings with plant response and uptake of K.
