Nodulation and mycorrhization of transgenic soybean after glyphosate application

Freitas Chagas Junior, AloisioRodrigues dos Reis, MarceloRodrigues dos Santos, GilAndrea Lemus Erasmo, EduardoFrança Borges Chagas, Lillian

The sensitivity of nitrogen-fixing bacteria like Bradyrhizobium spp with in relation to glyphosate can be influenced by the concentration of the herbicide. This study aims to evaluate the effects of two formulations of glyphosate, in two application periods, on nodulation and mycorrhization in a soybean of variety RR P98Y11, using greenhouse, in pots with capacity of 4 L with savanna soils. Six treatments were utilized using Roundup Ultra and Roundup Original with one and two applications, witness without herbicide and witness only with mineral nitrogen, in a completely randomized design. Four evaluations were done, every 15 days, to determine the plant height, shoot and root dry weight, number of nodules, nodule dry weigh and mycorrhizae. It was observed an increase on the number of nodules, with the use of Roundup Ultra until 15 days after the first application. After this period, the witness only with inoculants showed a larger number of nodules. Roundup Ultra had positive influences on the dry weight of nodules, regardless the number of applications. There was no influence of glyphosate formulation considering the mycorrhizal colonization.

1. Roundup
2. a do solo e Bioquímica do solo
3. Bradyrhizobium
4. Glycine max.