The 0.02M strontium chloride (SrCl2) and 0.05M citric acid solution (Sr‐citrate) was developed for the simultaneous determination of availability indices for plant nutrients from soils. The objective of this study was to compare the Sr‐citrate extracting solution with water, 0.002M SrCl2, 0.1M barium chloride (BaCl2), 0.1M hydrochloric acid (HCl), 1M ammonium acetate (NH4OAc), and Mehlich 3 soil extractants as predictors of plant‐available potassium (K) for alfalfa(Medicago sativaL.) in the greenhouse. The Sr‐citrate solution extracted more soil K than SrCl2and BaCl2but less than the other extractants. The Sr‐citrate solution was best for predicting K uptake from low cation exchange capacity (CEC < 15 cmolc/kg) soils and adequately predicted plant uptake from higher CEC soils and the relative yield of alfalfa in all soils. The relationship between Sr‐citrate K and plant uptake was slightly improved when boiling nitric acid (HNO3)‐extracted K or organic matter content was included in the multiple regression equation. The results of this study show that the Sr‐citrate procedure can adequately predict the amount of plant‐available K in soils.