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Use of ion exchange resins in soil and plant testing for micronutrient availability

Tejowulan, R.S., J.J. Schoenau and J.R. Bettany . 1994. In Soils and Crops Workshop Proc., pp 255-267. Univ. Saskatchewan


Much effort has been directed towards the development of soil and plant tissue tests, to determine the concentration of available micronutrients in soil and plant materials, quickly and accurately (Sims and Johnson, 1991; Jones, 1991; Martens and Lindsay, 1990). Extracting solutions containing a chelate or weak acid are commonly used to assess micronutrient availability in soils and plants. Realization that such methods often remove larger amounts of the available nutrient pool than do the plants, has led to concern about their accuracy as indices of plant availability. Ion exchange resins may be a more suitable approach to extracting ions from soils and plants than conventional extracting solutions. Earlier research has reported that ion exchange resin in a loose bead form can successfully extract the fraction of exchangeable Cu, Zn, and Mn that is taken up by plants during the growing period. However, the loose bead form suffers from separation problems and therefore is not suitable for routine analysis. With the presence of exchange resin in a membrane form however, extraction techniques may be potentially easier in routine analysis, and also more efficient because of the large surface area available for adsorption and exchange. The objectives of this research were : 1) To develop a new technique to extract bioavailable micronutrients from soil and plant tissue materials using ion exchange membrane, 2) To validate the developed techniques, and 3) To provide indexes of critical micronutrient levels in soils and plant tissue for the particular methods, crops, and micronutrients.