Leaching of S-metolachlor, terbuthylazine, desethyl-terbuthylazine, mesotrione, flufenacet, isoxaflutole, and diketonitrile in field lysimeters as affected by the time elapsed between spraying and first leaching event

Abstract

The effect of elapsed time between spraying and first leaching event on the leaching behavior of five herbicides (terbuthylazine, S-metolachlor, mesotrione, flufenacet, and isoxaflutole) and two metabolites (desethyl-terbuthylazine and diketonitrile) was evaluated in a 2011-2012 study in northwest Italy. A battery of 12 lysimeters (8.4 m(2) long with a depth of 1.8 m) were used in the study, each filled with silty-loam soil and treated during pre-emergence with the selected herbicides by applying a mixture of commercial products Lumax (4 L ha(-1)) and Merlin Gold (1 L ha(-1)). During treatment periods, no gravity water was present in lysimeters. Irrigation events capable of producing leaching (40 mm) were conducted on independent groups of three lysimeters on 1 day after treatment (1 DAT), 7 DAT, 14 DAT, and 28 DAT. The series was then repeated 14 days later. Leachate samples were collected a few days after irrigation; compounds were extracted by solid phase extraction and analyzed by high-performance liquid chromatography and gas chromatography-mass spectrometry. Under study conditions, terbuthylazine and S-metolachlor showed the highest leaching potentials. Specifically, S-metolachlor concentrations were always found above 0.25 µg L(-1). Desethyl-terbuthylazine was often detected in leached waters, in most cases at concentrations above 0.1 µg L(-1). Flufenacet leached only when irrigation occurred close to the time of herbicide spraying. Isoxaflutole and mesotrione were not measured (<0.1 µg L(-1)), while diketonitrile was detected in concentrations above 0.1 µg L(-1) on 1 DAT in 2011 only.

Assessment of Mesotrione Leaching Applied Alone and Mixed in Seven Tropical Soils Columns under Laboratory Conditions

“…Furthermore, the maximum percentage of mesotrione residues was found in the same layer according to the soil studied (Figure 1). These data are consistent with Milan et al [5] and Marín-Benito et al [19] that reported mesotrione had high leachabilityin the soil.…”

“…The data corroborate with Milan et al [5], that found the leaching of mesotrione applied in mixture with S-metolachlor and terbuthylazine averaged from 24 to 39% of that initially applied to columns of 0-40 cm of sandy soil [4] and can be detected at up to 1.8 m depth silt loam soil, although this was not quantified because of the low-dose application (150 g ha −1 ) and rapid dissipation (DT50 = 3-7 days).…”

“…Leaching of the commercial product Lumax ® , composed of mesotrione, S-metolachlor and terbuthylazine was evaluated in soil from Italy [4,5]. However, the potential interactions between herbicides when compared with the application of each herbicide alone were not fully investigated.…”

“…In addition, mesotrione is effective at controlling weeds resistant to other herbicides (e.g., ALS-acetolactate synthase enzyme inhibitors and triazines). Mesotrione is generally applied in a mixture with other herbicides, such as S-metolachlor and terbuthylazine [4,5]. However, mixtures of herbicides can alter sorption as well as microbial degradation rates, which lead to alterations in the rates of leaching [6].…”

Sequential use of the STICS crop model and of the MACRO pesticide fate model to simulate pesticides leaching in cropping systems

“…6b). In any case, the observed Smetolachor concentrations were higher than the 0.1 μg L −1 regulatory limit (Directive 98/83 EC 1998) which is consistent with the low value of its sorption coefficient (Table 3), and with several observations (e.g., Milan et al 2015). As for water percolation, the simulation of pesticide leaching in Lamothe was poor ( Fig.…”