| The Sodium adsorption ration (SAR) of soil can be calculated from measured Na+ concentration and predicted Ca2++Mg2+ (bivalent cation) concentration or from measured bivalent cation concentration and predicted Na++ concentration. In this study, four methods were used to estimate SAR of saline sodic soils in Songnen Plain, Northeast China by using two set of soil samples. First method, the bivalent cation concentration was calculated by the total cation concentrations (TCC) that was derived from the measured Na+ concentration and electrical conductivity (EC); second method, the Na+ concentration was calculated from the predicted TCC and measured bivalent cation concentration; third method, the bivalent cation concentration was calculated from the measured Na+ concentration and total anions concentrations (TAC); fourth method, the Na+ concentration was calculated from the measured bivalent cation concentration and TAC. The Results by T test for a paired samples were showed that: There was no significant difference between the calculated SAR and measured SAR (Ｐ>0.05). However, the slope of the regression between measured SAR and predicted SAR calculated from the first and third method was 0.66 and 0.79, respectively. This shown these methods by measured Na+ concentration and predicted bivalent cation concentration to estimate SAR with a poor accuracy. For the second and fourth method, the slop of the regression between measured SAR and predicted SAR was 0.96 and 1.10, respectively, which was very close to 1.0 with a high accuracy. So in practical use, suggested that methods by measured bivalent cation concentration and predicted Na+ concentrations to estimate SAR. |