INVESTIGADORES
ZABALOY Maria Celina
congresos y reuniones científicas
Título:
Evaluation of impacts of the herbicides glyphosate, 2,4-D and metsulfuron-methyl on microbial activity and functional richness of agricultural soils
Autor/es:
ZABALOY, MARÍA CELINA; PEREZ, M. TERESA; GARLAND, JAY L.; GÓMEZ, MARISA ANAHÍ
Lugar:
Córdoba
Reunión:
Congreso; XI Congreso Argentino de Microbiología; 2007
Institución organizadora:
Asociación Argentina de Microbiología
Resumen:
The intensive use of herbicides in agricultural soils of the Pampas region is a matter of environmental concern. However, information on the side-effects of agrochemicals on biological processes is lacking. We investigated the impacts of three widely-used, post-emergence herbicides (glyphosate, 2,4-dicholorophenoxyacetic acid (2,4-D) and metsulfuron-methyl) on soil microbial activity, culturable aerobic heterotrophic bacterial (AHB) density, and functional richness in several microcosms assays. Microbial activity was assessed by substrate-induced respiration (SIR), dehydrogenase activity (DHA) and fluorescein diacetate (FDA) hydrolysis. Functional richness was evaluated as the proportion of carbon sources utilized in microplates containing 33 substrates (16 carbohydrates, 8 carboxylic acids, 8 aminoacids, 1 aromatic compound), and TTC as redox dye. Three different types of soils were collected from agricultural fields located in the south of the province of Buenos Aires (Argentina), with reported history of herbicide application. In each microcosms incubation, soil was treated with an herbicide at a dose ten times higher than the recommended field application rates (glyphosate, 150 mg a.i kg-1; 2,4-D, 5 mg a.i kg-1; metsulfuron-methyl, 1 mg a.i kg-1) and incubated at 28ºC for up to 3 weeks. Measurements were done on an early time point (2-3 days after treatment) and weekly thereafter. In general, the results showed that the herbicides exerted no major effects on activity and metabolic richness of microbial communities of agricultural soils that had been previously exposed to these agrochemicals. Metsulfuron-methyl had the least pronounced effects on soil microbial community while 2,4-D showed early inhibitory effects on microbial activities. Several short-term effects of glyphosate on microbial activities and bacterial density were observed. The addition of glyphosate to the microcosms caused an early stimulation of SIR and AHB, while FDA and DHA showed dissimilar response in the soils assayed. Functional richness was slightly affected by glyphosate in the short-term. The addition of these herbicides at a dose ten times higher than the normal field application rates caused minor changes to soil microbial activity, bacterial density and functional richness. The specific changes varied among herbicides, with the effects of glyphosate most pronounced.