Ion Chromatography as an Alternative to Standard Methods for Analysis of Macro-nutrients in Mehlich 1 Extracts of Unfertilized Forest Soils
This study evaluates ion chromatography (IC) as an alternative to atomic absorption (AA) and inductively-coupled plasma spectromctry (ICP) for analysis of potassium (K), magnesium (Mg), and calcium (Ca), and and as an alternative to antimonylmolybdate colorimetry and ICP for analysis of phosphorus (P) macro-nutrients in Mehlich 1 extracts. Soils typical of pine forests in the southeastern United States were tested. IC correlates well with AA and ICP for K and Ca, but not for Mg, unless conditions are chosen that resolve Mg from manganese (Mn). IC does not correlate very well with colorimetry for P at extract levels below 2 mg kg-1 or in extracts with high levels of dissolved organic matter complexes of aluminum (Al) and iron (Fe). ICP results for P exceed both IC and colorimetry by 3-5 mg kg-1 for all soils tested. The merits of IC relative to AA, ICP, and colorimetry for forest soil testing are discussed.