Estimating the electrical conductivity of a saturated soil paste extract (ECe) from 1 : 1 (EC1 : 1), 1 : 2 (EC1 : 2) and 1 : 5 (EC1 : 5) soil : water suspension ratios, in calcareous soils from the Mediterranean Islands of Malta

Abstract

The standard method to determine soil salinity is by measuring the electrical conductivity (EC) of a saturated soil paste extract (ECe). Models that convert EC of soil:water suspensions (EC(soil:water)) to ECe are soil specific and are not universal models. This study aimed to develop models to convert EC(1:1; 1:2; 1:5) to ECe for the calcareous soil of Malta. Moreover, the effect that soil texture, carbonate and organic matter content might have on these models was investigated. Using 114 soil samples with contrasting textural, carbonate and organic matter characteristics, the general models followed the equation ECe = 10(a(logEC(soil:water))+b) with good correlation coefficients (r2 = 0.91–0.93, p < .001). Models specific to fine and medium textured soil, soils with carbonate content between 35% and 50%, and soils with organic matter content between 2.5% and 4.2% showed a higher correlation coefficient (mean r 2 = 0.96). Validation of the models using 22 independent soil samples showed that the general models are reliable (RMSE = 0.93, 0.87, 0.97 dS m−1; NSE = 0.96, 0.97 and 0.95 for 1:1, 1:2 and 1:5, respectively). Except for the models developed from coarse textured soil, all the parameter-specific models were reliable. This study suggests that the general models could be used for soils of Malta having contrasting characteristics except for those with high sand content.