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.

草甘膦占全球除草剂销量的四分之一，人们对其在土壤中的命运以及对植物造成非目标植物毒性的可能性越来越感兴趣。然而，评估土壤残留物对植物的草甘膦生物利用度仍然具有挑战性。在这里，我们证明薄膜技术 (DGT) 中的扩散梯度可以有效测量土壤环境典型边界条件下的可用草甘膦：pH 4-9、P 浓度为 20-300 μg PL ^-1和 NaHCO ₃浓度为 10 –1800 mg L ^-1 。在这项研究中，四种具有不同草甘膦吸附特性的土壤被施用了高达16 mg kg ^-1的草甘膦，并根据DGT-草甘膦浓度测量了对小麦和羽扇豆的植物毒性。当使用 DGT 草甘膦代替碱可提取（即总可提取）草甘膦时，不同土壤类型的小麦和羽扇豆的根伸长得到了改进的剂量响应曲线。沙质 Tenosol 中草甘膦总可提取浓度为 2.6 和 5.0 mg 草甘膦 kg ⁻¹ ，相当于 2.9 和 6.5 µg L ⁻¹ DGT 可提取草甘膦，与相比，羽扇豆（但不是小麦）的根长减少了 32-36%未经处理的对照。因此，DGT 是评估不同土壤中草甘膦植物毒性水平的一种有前景的方法。