Is exchangeable sodium content a better index of soil sodicity than exchangeable sodium percentage?: a reassessment of published data.

摘要

The Exchangeable Sodium Percentage (ESP) is the most widely used index of sodicity for the investigation of soil structural stability and for soil classification. However, sensitivity to levels of ESP varies across soil types. An alternative index is the Exchangeable Sodium Content (ESC), in which levels of sodium are expressed on an oven-dried soil basis rather than relative to the cation exchange capacity. The abilities of ESP and ESC to explain variation in soil structural stability across soiltypes were compared using 15 published datasets. The logarithm of soil structural stability was correlated significantly with the logarithm of ESP in only seven data sets, compared with 14 data sets that had significant correlations with the logarithm ofESC. In 10 of the datasets, between 15 and 60% more of the variation in structural stability was explained by ESC than ESP. In three of four combined data sets where common methodologies were used, ESC explained variation better than ESP, and there wasno difference in the fourth. It is concluded that ESC is a better index of soil sodium levels than ESP and should be used more widely.