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

Abstract

Herbicide leaching is influenced by soil physical and chemical properties as well as the prevailing climatic conditions. However, little is known about leaching of mixture of herbicides in the soil, especially in tropical regions like Brazil. The objective of this study is to evaluate the leaching of 14 C-mesotrione (cyclohexane-2-14 C-mesotrione) alone and in a mixture with S-metolachlor and terbuthylazine in seven tropical soil columns under laboratory conditions. These soils represented a wide range of properties with varying textures, cation exchange capacity (44 to 154 mmol c kg −1 ), pH (6.0 to 7.7), organic carbon content (0.58 to 27.32 g kg −1 ) and clay mineral contents (50 to 605 g kg −1 ), which are typical of tropical soils. Mesotrione residues were observed across all soil column layers (0-30 cm) in all evaluated soils by simulating 200 mm of water for 48 h. The application of mesotrione, alone or in a mixture, does not influence the leaching of this herbicide. Leaching of mesotrione ranged from low (up 15 cm) to very high (up 30 cm and leachate) in the tropical soils and may pose a potential groundwater contamination risk. In sand and loamy sand soil, the mesotrione was quantified in the leachate at all sampling times as above 80% of the amount initially applied. Thus, mesotrione application without the prior knowledge of the soil physical and chemical properties can result in inefficient weed control on field condition due to high leaching potentials.

Understanding the Environmental Behavior of Herbicides: A Systematic Review of Practical Insights

“…Regarding herbicide mixtures, Refatti et al [66] determined the leaching potential of herbicides used in the Clearfield® system for irrigated rice and concluded that mixtures of imazethapyr + imazapic, imazapyr + imazapic, and imazethapyr leached into the soil, reaching depths of up to 25 cm in floodplain soil. However, in a study conducted by Mendes et al [67], the application of mesotrione, alone or in a mixture with S-metolachlor and terbuthylazine, did not influence the leaching of this herbicide.…”

Crop sensitivity to mesotrione residues in two soils: Field and laboratory bioassays

“…However, the study on mesotrione leaching in soil of different texture (clay, loam, sandy loam and sandy soils; pH 6.4-7.2) showed low mobility of the herbicide applied to corn field at 150 g ai ha -1 (residues were mainly found in soil up to 10 cm at levels in range 6-13 μg kg -1 1 mo after the corn harvest) (Rouchaud et al, 2001). In contrast, mesotrione was detected up to 30 cm of tropical soil layer and its leaching was higher in more alkaline soils with low values of cation exchange capacity (CEC) and OC/clay content (Mendes et al, 2018). Barchanska et al (2012) indicated that mesotrione is easily degradable and can be eluted from soil with a heavy rainfall (47 mm m -2 ) making the residues detectable in soil only 1 wk after its application at a recommended rate.…”