Phytotoxicity of mesotriona in corn with Azospirillum brasilense associated nitrogen fertilization

Resumo

This study aimed to evaluate the phytotoxicity of the mesotrione herbicide in the initial development of maize inoculated with Azospirillum brasilense and associated with nitrogen fertilization. The treatments were: randomized blocks in a 2x3 factorial scheme, represented by maize with and without mesotrione application (192 g ha-1) and treatments: 1-inoculation of the seeds with A. brasilense; 2-Application in coverage of 140 kg ha-1 of N; And 3- A. brasilense + 140 kg ha-1 of N in cover applied at 26 days after sowing (DAS). The application of mesotrione was performed at 21 DAS, with evaluations performed up to 28 days after application (DAA). At 7 DAA a reduction of the net assimilation rate of CO2 in 35% in the plants with mesotrione was observed, as well as increase of the peroxidases activity and greater degradation of carotenoids in the mesotrione plants. At 14 DAA the mesotrione reduced the rate of CO2 net assimilation and transpiration, while at 28 DAA, lower plant height, leaf area and shoot dry mass were verified in herbicide plants. The inoculation with A. brasilense + N increased peroxidase activity at 7 DAA and helped maintain the transpiratory rate at 14 DAA. It is concluded that inoculation with A. brasilense + N can minimize the harmful effects caused by mesotrione in the initial development of corn.