Abstract

BOCCOLINI, Mónica Fabiola et al. Bacterial groups in a typical argiudol with application of glyphosate: influence on bacteria of nitrogen. Cienc. suelo [online]. 2019, vol.37, n.2, pp.225-237. ISSN 1850-2067.

Soil microorganisms are responsible for many functions and could be considered "biological markers" as these quickly reflect the negative effects of pesticides that are commonly used. This study evaluates the effect of two doses of glyphosate on soil microbial activity and carbon from microbial biomass, on the abundance of bacterial groups, and structure of the community of ammonia-oxidizing bacteria (AOB) in a typical Argiudoll. A bioassay was carried out with the agricultural soil from Marcos Juárez, Córdoba. The treatments were: soil without glyphosate (control); soil with application of 3,1 mg ai kg^-1 (field dose) and another of 31 mg ai kg^-1 (excess dose). At 3, 7, 14 and 21 days after the glyphosate application, the heterotrophic, cellulolytic, N-fixing and, nitrifying bacteria were counted, and microbial respiration (MR); carbon from microbial biomass (C-MB) and the enzymatic activity by fluorescein diacetate hydrolysis were determined. In addition, the genetic diversity of the AOB was determined by denaturing gradient gel electrophoresis. Bacteria related to the N cycle showed increases in the abundance with both doses of glyphosate, while the bacteria related to the C cycle did not show significant differences and, like MR, were conditioned by the incubation days. While the C-MB did not show differences probably due to the soil organic matter content (SOM). The enzymatic activity decreased with the highest dose of the herbicide, at 14 days. The diversity of AOB was greater at field dose and after 7 days. Under evaluated conditions, N cycle bacteria and its enzymatic activity showed greater sensitivity to glyphosate than other bioindicators. This study adds evidence to the glyphosate effects on soil microbiota which are variable and depend on edaphic factors, mainly SOM and the used doses.

Keywords : Bioindicators; Denaturing gradient gel electrophoresis (DGGE); Herbicide.