In the original procedure of J. L. Smith's method for determining potassium in soils, solid ammonium chloride is pulverized with soil sample and then mixed with calcium carbonate, The writers recommend to mix soil and calcium carbonate in advance, and the mixture is moistened with 15% NH₄Cl solution. Experimental results also show that the fusion can be done directly in a muffle of 700℃ without significant volatile of ammonium chloride.Potassium can be determined in a portion of water extract in flame photometer without the previous removal of Ca⁺⁺ ion. Results show good agreement with the original method.