Abstract—Researchers have long had trouble in measurement of Exchangeable Sodium Ratio (ESR) at salt-affected soils. this parameter are often determined using laborious and time consuming laboratory tests, but it may be more appropriate and economical to develop a method which uses a more simple soil salinity index. The aim of this study was to determine the relationship between exchangeable sodium ratio (ESR) and sodium adsorption ratio (SAR) in some salt-affected soils of Khuzestan plain. To this purpose, two experimental areas (S1, S2) of Khuzestan province-IRAN were selected and four treatments with three replications by series of double rings were applied. The treatments were included 25cm, 50cm, 75cm and 100cm water application. The statistical results of the study indicated that in order to predict soil ESR based on soil SAR the linear regression model ESR=0.2048+0.0066 SAR (R 2 =0.53) & ESR=0.0564+0.0171 SAR (R 2 =0.76) can be recommended in Pilot S1 and S2 respectively. Keywords—exchangeable sodium ratio, Khuzestan plain, salt- affected soils and sodium adsorption ratio. I. INTRODUCTION ALINE soils are of increasing importance both in Iran and world-wide. In Iran, approximately 44.5 M ha of arable land are affected by dry land salinity [1]. The sodium absorption ratio (SAR) of soil solution extracts has been an important tool for predicting the equilibrium exchangeable sodium ratio (ESR) in salt affected soils. The degree of sodium hazard in the soil has then been related to the soil ESR (U.S. Salinity Laboratory Staff, 1954) [2]. SAR is usually defined as: 2 2 2 + + + + = Mg Ca Na SAR (1) Where the cation concentrations are in meq/1 M. Siosemarde is with the PhD in Irrigation and Drainage Engineering, Water Engineering Department, Islamic Azad University (IAU), Mahabad Branch, Mahabad, Iran (e-mail: maroof_33m@yahoo.com). F. Kave is Associate Professor, Water Engineering Department, Islamic Azad University (IAU), Science & Research Branch, Tehran, Iran (e-mail: fhnkaveh@yahoo.com). E. Pazira is Professor, Soil Engineering Department, Islamic Azad University (IAU), Science & Research Branch, Tehran, Iran (e-mail: epazira675@yahoo.com). H. Sedghi is Professor, Water Engineering Department, Islamic Azad University (IAU), Science & Research Branch, Tehran, Iran (e-mail: hsedgh@yahoo.com). S. J. Ghaderi is Assistant Professor, Water Engineering Department, Islamic Azad University (IAU), Mahabad Branch, Mahabad, Iran (e-mail: ghaderi.jamil@gmail.com). The ESR is usually defined as: Na le Exchangeab - CEC Na le Exchangeab 100 × = ESR (2) Where CEC is the cation exchange capacity or calculated from the total exchangeable cations. The CEC and the exchangeable Na have traditionally been expressed in meq/100 g soil [3]. As shown in Eq. (2), for determining soil ESR, it is necessary to have soil Cation Exchange Capacity (CEC). But, as soil CEC are often determined using laborious and But, as soil CEC are often determined using laborious and time consuming laboratory tests [4,5]. The relationship between SAR and ESR has been used in expressions ranging in complexity from SAR - 100 SAR ESR = [6], which does not allow SAR to exceed 100, through a series of expressions discussed by Oster and Sposito (1980), to the empirical relationship; ) SAR 0.01475 0.0126 - ( + = ESR (3) As developed from statistical analysis of many soil sample data (U.S. Salinity Laboratory Staff, 1954). Previously researches report a relationship between the Sodium Adsorption Ratio (SAR) with a reported soil ESR and SAR [7-11]. The purpose of this study was to determine the relationship between exchangeable sodium ratio (ESR) and sodium adsorption ratio (SAR) in some salt-affected soils of northern Ahwaz Khuzestan plain. II. MATERIALS AND METHODS In all, soil samples were taken along the northern Ahwaz, Khuzestan province, south eastern Iran. Every soil sample was taken in lands with a high risk of salinization and/or sodification. Climate in this region is characterized by dry summers and winters, with 252.1 mm/year rainfall, and 3222.5 mm/year evapotranspiration. These conditions, in addition to the use of high to medium salt-content irrigation water and/or bad drainage, lead to an increased risk of salinization and/or sodification in agricultural areas. In this work, two experimental areas (Pilot 1 with silty clay texture & S 4 A 4 Will Cox classification and Pilot 2 with sandy loam texture & S 3 A 2 Will Cox classification) were selected and four treatments with three replications by series of double rings were designed. The treatments were included 25cm, 50cm, 75cm and 100 cm water application by Karoon River that Result of chemical analysis listed in Table 1. Prediction of Soil Exchangeable Sodium Ratio Based on Soil Sodium Adsorption Ratio M. Siosemarde, F. Kave, E. Pazira, H. Sedghi and S. J. Ghaderi S World Academy of Science, Engineering and Technology International Journal of Geological and Environmental Engineering Vol:4, No:10, 2010 454 International Scholarly and Scientific Research & Innovation 4(10) 2010 ISNI:0000000091950263 Open Science Index, Geological and Environmental Engineering Vol:4, No:10, 2010 publications.waset.org/12384/pdf