Questions regarding the application of pre-emergence herbicides for control weeds in eucalyptus are noteworthy due to the impact of this practice on the environment, particularly on soil microbial activity and beneficial micro-organisms such as mycorrhizal fungi and phosphate solubilizers. The aim of this research was to study the impact of applying herbicides sulfentrazone isoxaflutole and oxyfluorfen on mycorrhizal colonization, microbial biomass and microbial activity of two forest soils cultivated with eucalyptus. The trial was conducted in a greenhouse using two soils, one clay and sandy loam distributed in 12 dm³ pots. The 4x3 factorial design was used , with three herbicides (sulfentrazone, oxyfluorfen, isoxaflutole) over the untreated control and three assessments (5, 20 and 70 days after application (DAA)), in a completely randomized design with four replications . After herbicide application seedlings of the hybrid Eucalyptus grandis x Eucalyptus urophylla. We evaluated the microbial biomass of the soil respiration rate, the quotient and the metabolic potential of solubilization of inorganic phosphate at 5, 20 and 70 DAA. At 70 DAA verified the percentage of roots colonized by mycorrhizal fungi and spore viability in the soil. The sulfentrazone, isoxaflutole and oxyfluorfen as well as the time of application affected the microbiological indicators differently. In the sandy loam soil sulfentrazone was more harmful to microbial biomass, mycorrhizal colonization and microorganisms solubilizing inorganic phosphate. In clay soil, however, the application of the three herbicides did not affect microbial biomass, but reduced root colonization of eucalyptus by mycorrhizal fungi and the potential solubilization of inorganic phosphate. The sulfentrazone stood for caused an increase in the number of non-viable spores of mycorrhizal fungi in the soil.
herbicides; Eucalyptus grandis x Eucalyptus urophylla; mycorrhiza; phosphate solubilization; microbial biomass
