In order to set up a routine soil testing laboratory for advisory purpose, sample preparation and handling is very important. Potassium is one of the essential nutrients, whose handling’ has not been studied in Nigeria. Laboratory and greenhouse experiments were therefore set up to study the effect of sample preparation and handling on exchangeable K. The results have indicated that air drying at 72°F resulted in a significant increase in extractable K while even drying at 110°C for 24 hours resulted in similar values with those obtained for field moist samples. Correlation coefficients between K uptake by plants and exchangeable K determined from moist and oven dry samples were not significantly different from each other whereas there was significant correlation (r=0.904***) between K uptake and exchangeable K determined from air‐dry samples. Under wetting‐ and drying, there was an increase in soil K. The mechanism for this is not understood. Furthermore no significant difference exists between shaking of soil samples for 5 minutes and 60 minutes and storage for two years has no effects on extractable K.