The impact of glyphosate herbicides on soil microbial activity from the Carajás National Forest

Abstract

KEYWORDS Bioindicators Invasive plants Microbial respiration rate Metabolic quotient PALAVRAS-CHAVE Bioindicadores Plantas invasoras Taxa de respiração microbiana Quociente metabólico ABSTRACT:The objective of this study was to evaluate the impact of different glyphosate-based herbicide formulations on microbial activity of soils from Carajás National Forest. We tested three formulations of glyphosate, i.e., Roundup Original  , Roundup Ultra  and Roundup WG  that were applied in five doses: 0; 240; 480; 720 and 1440 g of active ingredient in acid equivalent ha -1 , with four replications. Herbicides were sprayed on pots containing 500 g of soil derived from the 0-10 cm layer of the study site. We determined the carbon from microbial biomass (C-MB), microbial respiration rate (MR) and metabolic quotient (qCO 2 ) at one and 28 days after herbicide application. No treatment affected the C-MB and MR at one and 28 days of incubation. There was no difference for qCO 2 at any dose of Roundup Ultra  and WG  formulations at one and 28 days of incubation. However, the qCO 2 was inhibited by the Roundup Original  at one day post treatment. This parameter was normalized at 28 days after herbicide application. The data indicate that no one of the treatments tested cause significant impact on soil microorganisms of the Carajás National Forest, suggesting that herbicide-based invasive weed control could be used. RESUMO: Objetivou-se com este estudo avaliar o impacto de diferentes formulações de herbicidas à base de glyphosate na atividade microbiana de solo da Floresta Nacional de Carajás. Foram testadas três formulações comerciais de glyphosate (Roundup Original

Efeito das estratégias de controle de plantas espontâneas na qualidade da matéria orgânica e fertilidade do solo

“…Furthermore, various authors (ARAÚJO; MONTEIRO;ABARKELI, 2003;TIRONI et al, 2009) have also reported an increase in C-CO 2 emissions after the application of herbicides. For example, Castilho et al (2016), who stated that the soil microbiota uses glyphosate as a carbon (energy) source, producing CO 2 in the short term. We therefore believe that the cumulative C-CO 2 respiration was intensified by each of the control strategies under evaluation.…”

The Risks Associated with Glyphosate-Based Herbicide Use in Planted Forests

“…Fletcher and Freedman [82] conducted laboratory studies with two leaf litter and one forest floor substrate and found that the threshold for glyphosate effects on litter decomposition was more than 50 times higher than residue concentrations that occur in the field after silvicultural herbicide treatments. In another laboratory study, Castilho et al [83] found that a range of glyphosate products, applied at doses within the range used in managed forests, had no significant impact on microbial activity in forest soils. Soil DT 50 's in the forest field studies discussed in the 'Fate in litter and soils' section above, were at the low end of the range reported in Table 2.…”