Correction of SAR in salt-affected soils of East Nile Delta (Egypt): Estimation of actual ion concentrations in soil solution

The Sodium Adsorption Ratios (SAR’s) were determined and corrected for ion-pairing and ion-pairing plus activities in saturation extracts of 124 soil samples collected from EL-Hosainiya plain East Nile Delta. The actual ionic concentrations, ionic activities, and ion-pair concentrations were determined using a special computer program. Sulphate ion-pairs occurred in relatively high concentrations with decreasing order of MgSO4 o > CaSO4 o > NaSO4 -. Of their total concentrations, the active forms of Ca and Mg were 42% and 50%, respectively. However, it was as much as 70% for Na. A significant change was observed in the SAR values when corrected for ion-pairing and activities. Corrected SAR values for ion-pairing plus activities were as 1.5 times as the uncorrected SAR values. A correction model for SAR values with respect to ion-pair concentrations and activities is performed in this paper.