Assessing plant-available glyphosate in contrasting soils by diffusive gradient in thin-films technique (DGT)

Zhe Weng, Michael T. Rose, Ehsan Tavakkoli, Lukas Van Zwieten, Gavin Styles, William Bennett, Enzo Lombi

    Research output: Contribution to journalArticlepeer-review

    9 Citations (Scopus)

    Abstract

    Glyphosate represents one quarter of global herbicide sales, with growing interest in both its fate in soils and potential to cause non-target phytotoxicity to plants. However, assessing glyphosate bioavailability to plants from soil residues remains challenging. Here we demonstrate that the diffusive gradient in thin-films technique (DGT) can effectively measure available glyphosate across boundary conditions typical of the soil environment: pH 4–9, P concentrations of 20–300 μg P L−1 and NaHCO3 concentrations of 10–1800 mg L−1. In this study, four soils with different glyphosate sorption properties were dosed with up to 16 mg kg−1 of glyphosate and phytotoxicity to wheat and lupin was measured against the DGT-glyphosate concentrations. An improved dose response curve was obtained for root elongation of wheat and lupin across soil types when DGT-glyphosate was used instead of alkaline-extractable (i.e., total extractable) glyphosate. Total extractable glyphosate concentrations of 2.6 and 5.0 mg glyphosate kg−1 in the sandy Tenosol, equivalent to 2.9 and 6.5 μg L−1 DGT-extractable glyphosate, reduced the root length of lupins (but not wheat) by 32–36% compared with the untreated control. DGT is therefore a promising method for assessing phytotoxic levels of glyphosate across different soils.

    Original languageEnglish
    Pages (from-to)735-744
    Number of pages10
    JournalScience of the Total Environment
    Volume646
    Early online date20 Jul 2018
    DOIs
    Publication statusPublished - 01 Jan 2019

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