Relationship between Electrical Conductivity of the Saturation Extract with other Salinity Indices in Some Salt Affected Soils of Golestan Province

Background and objectives It is estimated that 350000 ha of soils of Golestan province are affected by different degrees of salinity. The use of salinity sensors for estimating the amount of salts in the field is increasingly common; however, laboratory analysis of aqueous extracts of soil is still the most common technique for assessing salinity and other potential hazards. Salinity is expressed in a number of ways, depending on the method and purpose of the measurements. Electrical conductivity (ECe), total dissolved salts (TSS) and total dissolved solids (TDS) called salinity parameters. Direct measurements of some of these parameters are time-consuming and costly involving errors. Therefore, investigators attempt to estimate them from other parameters which could be measured more easily. The aim of this study was to suggest some reliable simple equations for estimating salinity indices in salt affected soils of Golestan province using electrical conductivity .
Materials and Methods The study area is located in the Northeast Iran (Golestan Province). 43 composed soil samples were collected from the 0–30 cm of salt-affected soils. All samples were air-dried and ground to pass a 2-mm mesh sieve. Concentrations of calcium, magnesium, sodium, potassium, chloride, sulphate, bicarbonate and carbonate in the saturation extracts of soils were determined. The concentration of the above cations and anions were used to calculate ionic strength by using the relationship I=1/2∑CiZi2 where C and Z are concentration and valance, respectively. Then, the relationship between I and ECe was examined. Ionic strength was also estimated using the relationship between I and ECe as proposed by Griffinn and Jurinak, i.e. I=0.013 EC. Other simple equations to estimate the salinity parameters for the salt-affected soils of Golestan province were also find.
Results Results showed that the salinity (TSS, ionic strength and concentration of chloride ion) parameters are in close relation with the ECe. The following equations are proposed for estimating parameters of TSS (mmolcL-1), ionic strength (molL-1) and concentration of chloride ion (mmolcL-1) from ECe(dSm-1):

LogTSS = 1.1489 + 0.9214 log ECe (R2= 0.960, SEE=0.083)
I = 0.0124 ECe + 0.0488 (R2= 0.96, SEE=0.042)
LogCl- = 1.1555 log ECe + 0.5042 (R2= 0.89, SEE= 0.19)

Conclusion According to the results, salinity (TSS, ionic strength and concentration of chloride ion) parameters are in close relation with the ECe. These relationships are may vary depending on the type of soil. This study reported a linear relationship between ionic strength and electrical conductivity which was employed to predict ionic strength using soil solution samples. The results also indicated that there is a good agreement and correlation between EC and Cl- concentration in soil solution samples.