Are bioassays and Analytical Methods Equivalent to the Application of Herbicide Leaching to Sugarcane Crops?

Herbicide leaching studies are extremely important to evaluate the environmental behavior of these products in the environment. However, there are no equivalence analyses in the literature of the most commonly used methods: bioassays and HPLC. Therefore, the present study aimed to analyze the leaching of the herbicides imazapic (147 g ai ha⁻¹) and sulfentrazone (800 g ai ha⁻¹) using bioassays with Cucumis sativus L. and HPLC/MS/MS methodologies when applied to sugarcane straw and directly on the soil and subjected to different periods of drought. Two experiments were performed with soil columns that followed a completely randomized design, with four replicates, in a 3 × 4 × 2 factorial scheme, with three treatments (0, 30 and 60 days after the application), four soil depths (0–0.05; 0.05–0.1; 0.1–0.15 and 0.15–0.2 cm) and in the absence of straw or with 10 t ha ⁻¹ straw for each of the herbicides: imazapic and sulfentrazone. The bioassay and HPLC methodologies were equivalent in the leaching of imazapic to a depth of 0.1 m. Sulfentrazone showed low to moderate leaching, since from 0.10 cm, leaching was inexpressive in both methods, and in the 0.15–0.2 m layers in the HPLC methodology, the amount of herbicide detected was zero. Therefore, both methodologies can be considered equivalent in the study of herbicide leaching because even though they are different quantitative (HPLC) and qualitative (bioassay) methods, they resulted in interpretations similar in relation to the behavior of herbicides in the soil.