Evaluation of bioavailability of light rare earth elements to wheat (Triticum aestivum L.) under field conditions

Current bioavailability assessments of light rare earth elements (LREEs) are often carried out under greenhouse conditions. This work was to identify which soil properties are mostly related to LREE bioavailability and what extraction method is the most promising approach for assessing bioavailability of LREEs to wheat under field conditions. A comparison was made between four commonly used extractants (DTPA, EDTA, CaCl2 and CH3COOH), and the results suggested that the LREE concentrations in wheat roots significantly Correlated with soil pH and amorphous Fe oxide contents in soils, but were independent of soil organic matter (SOM), crystalline Fe and Mn oxide contents, and cation exchange capacity (CEC). The contents of LREEs in shoots were independent of any soil properties. Both DTPA- and EDTA-extractable LREEs were significantly correlated to LREE concentrations in wheat roots and shoots. DTPA extractable LREEs were comparable to LREEs in wheat roots, however, the EDTA exetractable LREEs overestimated the LREE accumulation in wheat roots. Neither root nor shoot LREEs showed significant correlation with CH3COOH extractable LREEs, suggesting that the CH3COOH extraction method was not suitable for predicting LREE bioavailability. CaCl2 method was unable to estimate the LREE bioavailability due to poor data distribution in correlation analysis. Overall, DTPA extraction method was preferred to other extraction methods for estimating bioavailability of LREEs to wheat. (C) 2007 Elsevier B.V. All rights reserved.