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Assessing sulphur availability in soil using ion exchange membranes

Schoenau, J.J., P. Qian and W.Z. Huang . 1993. Sulphur in Agriculture. 17: 13-17


Extraction of plant nutrient ions from soils with ion exchange resins provides one of the more reliable indexes of plant availability, as ion exchange resins can closely simulate the nutrient removal action of plant roots. Anion exchange resins contain positively charged surface functional groups that attract anions, including SO4. Thus, exchange resins act as a sink for ions when placed in a suspension of soil and water. The resin continually removes any ions that come into solution, thus preventing equilibrium of the ions between the solid phase and solution. Due to their mode of action, resins are thought to be a universal index of ion availability, as compared to chemical-based extracting solutions, which may be limited in scope due to their ability to remove only specific fractions. Exchange resins offer an additional feature in that they can exchange directly with ions in the solid phase when placed in direct contact with soil.