Comparison of single and sequential soil extractions for predicting copper phytotoxicity

Abstract

Abstract Phytotoxicity of copper (Cu) and other heavy metals is related to their forms in soil. In this study, different forms of Cu in the soil solid phase, i.e. exchangeable, sorbed, organically bound, precipitate, and residual forms were measured, using a sequential fractionation procedure (SFP), in a soil amended with various rates of Cu. The relationships between different forms of Cu by SFP in soil or Cu extractable by Mehlich 1 (M1) and Mehlich 3 (M3) and accumulation of Cu by citrus roots or shoots were examined. The results showed that Cu mainly existed in the organic fraction. An increase in soil pH decreased the organic fraction and increased the precipitate fraction of Cu. Copper concentration in citrus root was found to correlate with the water soluble, organic, or precipitate fractions of Cu in the soil. Multiple regressions using different forms of Cu in soil gave the same prediction of Cu concentration in citrus root as that using Ml‐ or M3‐extractable Cu.