Impacto de sulfentrazona, isoxaflutol e oxyfluorfem sobre a microbiota de dois solos florestais

Abstract

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 microorganisms such as mycorrhizal fungi and phosphate solubilizing microorganisms. The aim of this study was to evaluate 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 experiment was conducted in a greenhouse using two soils (clayey and sandy loam) distributed in 12 dm 3 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 were transplanted. We evaluated the microbial biomass, respiration rate, metabolic quotient and the 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. However, in clayey soil, the application of the three herbicides did not affect microbial biomass, but the root colonization of eucalyptus by mycorrhizal fungi and the potential solubilization of inorganic phosphate were reduced. The sulfentrazone caused an increase in the number of non-viable spores of mycorrhizal fungi in the soil.Key words: herbicides, Eucalyptus grandis x Eucalyptus urophylla, mycorrhiza, phosphate solubilization, microbial biomass.Impacto de sulfentrazona, isoxaflutol e oxyfluorfem sobre a microbiota de dois solos florestais ResumoQuestões referentes à aplicação de herbicidas em pré-emergência das plantas daninhas na cultura do eucalipto merecem destaque devido ao impacto dessa prática no ambiente, principalmente sobre a atividade microbiana do solo e micro-organismos benéficos, como os fungos micorrízicos e os solubilizadores de fosfatos. Objetivou-se estudar o impacto da aplicação dos herbicidas sulfentrazona, isoxaflutol e oxyfluorfem sobre a colonização micorrízica, biomassa e atividade microbiana de dois solos florestais cultivados com eucalipto. O ensaio foi conduzido em casa de vegetação utilizando um solo argiloso e um solo francoarenoso distribuídos em vasos de 12 dm 3. O esquema fatorial utilizado foi 4 x 3, sendo três herbicidas (sulfentrazona, isoxaflutol e oxyfluorfem) mais a testemunha e três avaliações (5, 20 e 70 dias após a aplicação -DAA), no delineamento inteiramente casualizado com quatro repetições. Após a aplicação dos her...

Effect of pre-emergent graminicide herbicides on germination and early development of native species

“…In the research by Brighenti & Muller (2014), the authors observed that herbicide isoxaflutole was the most phytotoxic herbicide for Khaya ivorensis and Toona ciliata, where all the variables evaluated presented a statistical difference to the control and the phytotoxicity levels were higher than those of other herbicides. Silva et al (2014) add that products applied in the pre-emergence of weeds, such as isoxaflutole, reach the soil directly and may cause greater damage by increasing the risk of exposure of soil phosphatesolubilizing microorganisms. The authors also noted that the application of isoxaflutole reduces root colonization of eucalyptus seedlings by arbuscular mycorrhizal fungi, also decreasing the potential for inorganic phosphate solubilization, directly affecting the early growth of the species.…”

Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides

“…Additionally, contamination by atrazine in the rhizosphere may favor the synthesis of phosphate-solubilizing enzymes and dehydrogenases (Huang et al, 2009). Sulfentrazone impairs the mycorrhizal colonization process in some tree species (Silva et al, 2014). The lower mycorrhizal colonization observed in T. hirta was inversely related to the higher biomass of this plant growing in soil with atrazine (see Figure 1).…”

Sulfentrazone: Environmental Dynamics and Selectivity

“…In addition to persistence, sulfentrazone may adversely affect the soil microbiota (Vivian et al, 2006). Silva et al (2014) observed that sulfentrazone was harmful to the microbial biomass, mycorrhizal colonization, and organic phosphate solubilizing microorganisms in soils cultivated with eucalyptus. Also, nodulation and fixation of nitrogen can be partially impaired by the application of sulfentrazone (Arruda et al, 2001).…”