Behaviour of sulcotrione and mesotrione in two soils

The behaviour of sulcotrione, a recently introduced triketone herbicide, in various soil types was studied under laboratory conditions. In particular, degradation and sorption processes were examined on Ghent and Perpignan soils. Kinetics showed that the degradation of sulcotrione was influenced by biotic and/or abiotic factors. Half-lives ranged between 45 and 65 days. Among the degradation compounds identified were 1,3-cyclohexanedione (CHD) and 2-chloro-4-mesyl benzoic acid (CMBA), previously described as hydrolysis products, and, under special conditions, a derivative of phenylheptanoic acid (PHD). This new degradation product suggested that sulcotrione could follow two possible pathways in the soil, as in water. During the sorption study, a moderate retention of sulcotrione and CMBA relative to CHD and PHD, which were highly adsorbed whatever the soil type, was reported. Experiments carried out under the same conditions for sulcotrione and mesotrione, another triketone herbicide recommended in maize culture, made it possible to compare the two triketones and to conclude that they exhibited relatively similar behaviour in the soil, i.e. that their leaching potential needs to be properly addressed and risks evaluated.