Comparison of Mehlich-3 and Ammonium Acetate Extractable Calcium and Magnesium in Kansas Soils

The use of the Mehlich-3 (M3) soil test procedure to assess plant availability numerous macro and micronutrients has become common at testing labs across US. is used for tests phosphorus (P) potassium (K) in Kansas; however, data other base cations existing methods are scarce Kansas soils. objective this study was investigate relationship between M3 ammonium acetate (AA) extractable calcium (Ca) magnesium (Mg). Regression analyses indicate a near 1:1 linear M3-Mg AA-Mg wide range pH organic matter (SOM) contents. M3-Ca AA-Ca relatively constant acidic neutral However, extracted substantially more Ca higher analysis indicates that diverge exponentially 7.3 higher. Given current interpretation as measure exchangeable Ca, these results suggest may extract from non-exchangeable soil-Ca pools soils with above levels. Based on results, should not be or estimate cation exchange capacity (CEC) 7.3, values likely overestimated.