Evaluation of Mehlich‐3 for determination of cation exchange capacity in Kansas soils

Abstract Soil testing laboratories across the United States have implemented Mehlich‐3 (M3) extraction method for phosphorus (P) and other nutrients. Though M3 is known to work well as a multinutrient extractant, it raises concerns measuring exchangeable cations, particularly in calcareous soils. The objectives of this study were (a) evaluate an extractant base cations Kansas soils, (b) identify range soil pH where may be suitable replacement ammonium acetate (AA), (c) examine relationship between cation exchange capacity (CEC) summation CEC displacement. A was conducted evaluating 308 soils collected from extracted using both AA methods. Cation estimated approach measurements AA, displacement method. Results indicate strong correlation among methods K, Mg, Na ( R 2 = .98, .96, .97, respectively). However, these relationships considerably weaker extractable Ca .78), higher extracts high Estimated also affected by method, with critical value 7.3. Extractable below 7.3 showed .9). Using can improve turnaround time sample analysis laboratories. use procedure or above will likely result overestimation CEC.