Phytotoxicity of Mesotrione Residues on Sugar Beet (Beta vulgaris L.) in Agricultural Soils Differing in Adsorption Affinity

The phytotoxic effects of mesotrione residues on sugar beet (Beta vulgaris L.) were determined in two agricultural soils (humofluvisol and hipogley) in order to show the relevance of soil characterization in crop rotation practice. Soils were treated with mesotrione at seven rates that simulated the levels of mesotrione in soil considering its field half-life. The visual injury and reduction in fresh weight and total carotenoid content were determined during the three-week cultivation in plastic pots under controlled conditions. The Freundlich isotherm model was used to reach the adsorption parameters of mesotrione in both soils. Humofluvisol showed at least twice as less adsorption affinity for mesotrione as hipogley. The effective dose (ED50) of mesotrione for 50% reduction in sugar beet fresh weight content was 5.9 g a i ha−1 in hipogley and 4.4 g a i ha−1 in humofluvisol. The ED50 for 50% reduction in total carotenoid content was 4.7 g a i ha−1 in hipogley and 2.1 g a i ha−1 in humofluvisol. The crop rotation has to be performed considering the soil characteristics due to its effect on the bioavailable amount of mesotrione residues in soil resulting in different levels of crop injury in two soils at the same rate.