Soil test potassium (K) for New Mexico cotton growers usually returns a high value for ammonium acetate extractable K. Despite high soil test K many commercial soil test laboratories recommend the addition of potash (K₂O) fertilizer. It appears that soil test laboratories are using basic cation saturation ratios to assess the relative availability of potassium to cotton. Water extractable potassium used by New Mexico State University may avoid the confusion this causes cotton producers. Grid sampled cotton fields were assessed for relationships between water and ammonium acetate (NH₄OAc) extractable potassium. Soil samples were also tested for exchangeable calcium (Ca) and magnesium (Mg). Cotton yield and lint quality was also assessed for each grid point for comparison to soil test parameters. Clay textured soil samples exhibited a positive relationship between ammonium acetate and water extractable K. The Ca:Mg ratio had no effect on lint yield or quality. Water extractable K may be a better method to assess K sufficiency since the interpretation considers K less than 60 mg kg^-1 to be deficient for cotton.