Defining a standard method to measure the total and bioavailable concentration of fluorine in New Zealand soils

To define a method for quantification of the bioavailable concentration of F in soil, samples were extracted with water, 1 mol L−1 HCl, 0.01 mol L−1 CaCl2, 0.01 mol L−1 KCl, and 1 mol L−1 NH4Cl. The correlation between 0.01 mol L−1 CaCl2, 0.01 mol L−1 KCl, and water extracted F concentrations were significant (p < 0.05), and extracted the same soil F fractions. Results were normalised to the water-extractable concentration to compare recovery as a function of soil order. The recovery percentage of 0.01 mol L−1 CaCl2 was high compared with water for soils which have high Al and Fe contents. We propose that 0.01 mol L−1 CaCl2 extraction should be adopted as a standard method to assess the bioavailable F concentration of New Zealand pastoral soils.