Use of reference soils in determinations of 0.01 m calcium chloride available metals

There are few readily available standard reference soils for which 0.01 M calcium chloride (CaCl2) soil extraction available metals data are available. This study assessed the ease with which new available metals data could be generated for reference soils. Data on 0.01 M CaCl2 available elements for four reference soils from the Wageningen Evaluating Programs for Analytical Laboratories and three reference soils from the Australasian Soil and Plant Analysis Council proficiency testing program are presented. It is difficult to generate new 0.01 M CaCl2 available metal values for standard reference soils, because trace element concentrations are low and measurements have relatively high variability. We suggest that laboratories can use reference soils as quality control samples in the analysis of 0.01 M CaCl2 available metals by reporting recoveries for major elements (e.g., potassium [K], magnesium [Mg], and sodium [Na], for which reference values are of high reliability) to provide assurance of acceptable extraction efficiency.