Comparison of analytical methods in testing soil fertility

Analytical methods for testing soil fertility were compared in a material of 430 topsoil samples. The samples were analyzed for particle-size distribution, organic carbon content, pH(CaCl2), exchangeable Ca and Mg extracted with 1 M ammonium acetate (pH 7) and 1 M KCI, exchangeable K extracted with 1 M ammonium acetate (pH 7) and P extracted by the Bray 1 method. These soil properties were compared with the soil textural class and humus content class estimated visually, pH (H2O) and Ca, Mg, K and P extracted with acid ammonium acetate. The estimation of soil textural class was quite successful, but the content of organic matter was frequently underestimated. pH (H2O) and pH(CaCl2) were highly correlated and 95 % of the variation in pH (H2O) was explained by pH(CaCl2). Exchangeable Ca together with pH(CaCl2) explained about 90 % of the variation in Ca extracted with acid ammonium acetate. Exchangeable Mg explained about 70 % of the variation in Mg extracted with acid ammonium acetate. Exchangeable K explained 90 % of the variation in K extracted with acid ammonium acetate. The Bray 1 P and pH(CaCl2) explained 60 % of the variation in P extracted with acid ammonium acetate. pH(CaCl2), clay and organic carbon content explained 72—83 % of the variation in Ca. Mg, K and P were not highly dependent on pH, particle-size distribution and organic carbon content of soil