Estimating Exchangeable Sodium Percentage from Sodium Adsorption Ratio of Salt-Affected Soil in the Songnen Plain of Northeast China

Soil exchangeable sodium percentage (ESP) and sodium adsorption ratio (SAR) are commonly used to assess soil sodicity. Correlation between ESP and SAR of saturated pasted extract (SAR(e)) or of 1:5 (m:m) mixture soil to water (SAR(1:5)) has been documented to predict ESP from SAR. However limited studies have been undertaken to model soil ESP based on soil SAR in the Songnen Plain, Northeast China. In this study, 117 soil samples were used to predict ESP from SAR(e) and SAR(1:5) of salt-affected soils in western Songnen Plain. Soil ESP was highly related (r(2) > 0.76, P < 0.001) with SAR(e) and SAR(1:5). ESP of salt-affected soils in the Songnen Plain could be predicted using a logarithmic regression equations of ESP = 10.72 . ln(SAR(e))-15.36 and ESP = 11.44 . ln(SAR(1:5)) + 5.48.