Relationship and Predictive Performance of Low-Cost EC 1:5 Measurements for Estimating ECe in Soil Salinity Assessment
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Abstract
The standard method for evaluating soil salinity is the determination of electrical conductivity (EC) of the saturated soil paste extract (ECe) which requires considerable technical expertise. Simpler EC measurement methods that can effectively classify soil salinity levels would be highly beneficial for routine monitoring. This study aimed to compare the analytical performance of the standard ECe method with alternative methods, including EC 1:5 measured in the laboratory (EC 1:5 Lab), EC 1:5 measured using an inexpensive pen-type EC meter (EC 1:5 pen-type) and a field soil EC test kit (EC test kit). A study was conducted on saline-affected soils at 32 locations in northeastern Thailand, with a total of 194 samples collected. The results demonstrated strong linear relationship between ECe and both EC 1:5 Lab and EC 1:5 pen-type measurements, with coefficients of determination (R²) 0.82 and 0.83, respectively. The results revealed that EC 1:5 measured using an EC pen-type meter could be used to predict ECe using a linear regression equation. Model performance was more reliable in low to moderate salinity ranges (ECe <4 dS/m; Residual values −1.93 to 5.87 dS/m), whereas prediction uncertainty increased at higher ECe levels (ECe >4 dS/m; Residual values −4.47 to 6.26 dS/m) indicating a tendency of the model to underestimate ECe at higher salinity levels. Calibration is recommended for the inexpensive pen-type EC meter prior to use to enhance measurement accuracy. As the EC test kit provides semi-quantitative discrete interval data, it is not suitable for quantitative prediction of ECe. However, the EC test kit is capable of screening saline soil at the field level. The soil salinity classification accuracy was 88.14% when compared to the laboratory-determined ECe values.
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King Mongkut's Agricultural Journal
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