Csillag, J., T. Tóth, and M. Rédly. 1995. Relationships between soil solution composition and soil water content of Hungarian salt-affected soils. Arid Soil Research and Rehabilitation. 9:245-260. Soil solution fractions retained in the soil with suctions not reaching -1500 kPa were centrifuged from three salt-affected soils. Hyperbolic relationships were set up in a wide soil water content range (from -250 kPa water potential to 1:10 soil:water ratio) between water content and electrical conductivity as well as concentrations of the dominant ions present in the liquid phase. It was shown that the parameters of the equations reflected on the salt content and composition of the soils, as well as on the change of the solubilities of the salts and ion-exchange processes with soil water content. Ion-pair concentrations and "free" ion activities were computed by taking into account the electrostatic interactions of ions in the solution. Na+/divalent cation ratio (SAR) was expressed from cation concentrations and activities. It was shown that depending on salt content and composition, as well as on water content of the soil 1.: the ratio of ion activities to concentrations was very variable (in some cases, at field capacity, in concentrated solutions, divalent ions' activities were even 6 times lower than concentrations); 2.: SAR was always (at field capacity, for example, nearly 2 times) higher if it was calculated from activities, and increased more with decreasing soil water content than SAR obtained from measured cation concentrations.