Estimating cation exchange capacity from agronomic soil tests

Article: Estimating cation exchange capacity from agrnomic soil tests: Comparing Mehlich-3 and ammonium acetate sum of cations.

Authors: Mattila, Tuomas & Rajala, Jukka.

Publication: Soil Science Society of America Journal

Year: 2021

Soil cation exchange capacity (CEC) measures the soil’s ability to hold and release nutrients. Because measuring CEC is laborious, faster methods to estimate CEC from soil samples have been developed. In this study, the results from two common estimation methods were compared with a dataset of 48 soil samples. The compared estimation methods differ in their extraction: Mehlich-3:a is commonly used in the USA, AAc in Europe. Based on the results, these traditional methods underestimate measured cation exchange capacity by 36% for Mehlich-3 and 24% for AAc. Thus, the CEC estimation methods should be updated. The estimation can be improved by including aluminium content (leads to 12% overestimate) or by developing the mathematical model used (3% overestimate).

Offering land managers accurate information allows them to understand their soils’ potential to store and release nutrients and to make better decisions on liming and soil amendment.