Modified Ion Exchange Resin Method for Extraction of Micronutrient Cations from Soils

Abstract

ABSTRACT Different chemical extractants and ion exchange resins are used to assess the bioavailability of soil nutrients for crop plants. The major problems associated with the use of IER in soil testing are their reusability and the difficulties encountered in their separation from the soil being extracted. We addressed these difficulties by encapsulating a weakly acidic cation exchange resin and weakly basic anion exchange resin in separate dialysis membrane pouches and suspending them together in a cellulose extraction thimble during extraction. The suitability of this method has been evaluated for diverse types of soils widely varying in physicochemical properties. The standardization of protocol revealed that the ideal conditions for extraction of micronutrients were: 20:40 soil water ratio and 4 h extraction at 25°C in a shaker incubator at 120 rpm. This simple modified ion exchange resin method can be used multiple times for routine soil tests in laboratories for extraction of cationic micronutrients. The soil extracts can be analyzed for cationic micronutrients. The coefficients of determination (R2) between resin extractable- and diethylene triamine pentaacetic acid extractable- nutrients were 0.31, 0.59, 0.67, and 0.88 for Zn, Cu, Fe, and Mn, respectively.