Activity of an element is a better predictor of plant growth response than its concentration. Ionic strength of the soil solution is an important property that is required to calculate ionic activity. Since its calculation requires measurement of all major cations and anions in solution, an alternative approach was sought to estimate it on the basis of a single measured property of solution. Griffin and Jurinak reported a linear relationship between ionic strength and electrical conductivity which was employed to predict ionic strength using soil solution samples from a wide range of soils subjected to varying treatments with respect to source of amendment, concentration of supporting solution, soil moisture content, and duration of incubation. This study has shown a very close agreement between ionic strength predicted using the Griffin-Jurinak relationship and the ionic strength calculated using concentration and valence values for all cations and anions in solutions. Furthermore, for the conditions of soil solutions from variable charge soils, the Griffin-Jurinak relationship was modified.
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