A pot culture experiment with exhaustive cropping of maize was conducted to determine the minimal level of exchangeable K and contribution of different K fractions to total uptake by the crop in 19 soils of West Bengal. The mean exchangeable K value decreased from 30-350 mg kg-1 to a constant minimal level of ranged 26.76-93.55, with an average of 62.9. Highest release of K from non-exchangeable sources occurred in the soil of quickest decrease of exchangeable K to its minimal level. Positive significant correlations between the percentage clay content and exchangeable K at minimal level and the K released from non-exchangeable sources were observed. Non-exchangeable K uptake was significantly correlated with total K removed by the crop and minimal exchangeable K level.