Soil microbial communities and glyphosate decay in soils with different herbicide application history

KEREN HERNÁNDEZ GUIJARRO; VIRGINIA APARICIO; EDUARDO DE GERÓNIMO; MARTÍN CASTELLOTE; EVA L. M. FIGUEROLA; JOSÉ LUIS COSTA; LEONARDO ERIJMAN

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018

0048-9697

This study evaluates the glyphosate dissipation under field conditions in three types of soil, and aims to determine the importance of the following factors in the environmental persistence of herbicide: i) soil bacterial communities, ii) soil physicochemical properties, iii) different land-use history with distinct exposure to the herbicide. A pristine soil without previous record of GP application (P0) and two agricultural soils, with 5 and more than 10 years of GP exposure (A5 and A10) were subjected to the application of glyphosate at doses of 3 mg.kg-1. The concentration of GP and AMPA was determined over time and the dynamics of soil bacterial communities was evaluated using 16S ARN ribosomal gen amplicon-sequencing. The GP exposure history affects the rate but not the extent of GP biodegradation in soils. The herbicide was degraded rapidly, but P0 soil showed a dissipation rate significantly lower than soils with agricultural history. AMPA concentration increased over time and remained at high levels until the end of the experiment, denoting higher persistence than the parental compound. In the pristine soil, a significant increase in the relative abundance of Bacteroidetes was observed in response to herbicide application. More generally, all soils displayed shifts in bacterial community structure, which nevertheless could not be clearly associated to glyphosate dissipation, suggesting the presence of redundant bacteria populations of potential degraders. Yet the application of the herbicide appears to prompt a partial disruption of the bacterial association network of unexposed soil. On the other hand, higher values of Kd and Kf in the P0 soil, point to the relevance of CEC, clay and organic matter to the capacity of soil to adsorb the herbicide, suggesting that bioavailability was a key factor for the persistence of GP and AMPA. These results contribute to understand the relationship between bacterial taxa exposed to the herbicide, and the importance of soil properties as predictors of the possible rate of degradation and persistence of glyphosate in soil.