Dinâmica do Fomesafen no solo e impacto de Tiametoxam e Fomesafen sobre três espécies de macrófitas aquáticas / Dynamics of fomesafen in soil and impact of thiamethoxam and fomesafen on three freshwater macrophytes

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

17/08/2011

RESUMO

Pesticides are very important to the modern agriculture. However, nowadays, with their increasing use, sometimes indiscriminately, there is also an increasing concern about their soil and water contamination. Fomesafen (herbicide) and thiamethoxam (insecticide) are organic compounds with very different physicochemical properties, but both are used in crops of great importance in Brazilian agriculture. Fomesafen, can have some residual effect in soils, and it can cause injury to sensitive crops in areas where it has been previously used, or even in areas that have been contaminated by drifting during application in some adjacent area. On the other hand, thiamethoxam, used as an insecticide, has also been suggested as a growth-promoter to some cultures. Therefore, the objectives of this study were: i) to evaluate the sorption, dissipation, leaching and residual effect of fomesafen in samples of a dystrophic Red-Yellow Latosol (LVAd) and a distroferric Red Latosol (LVdf) amended with vinasse, sewage sludge and phosphate. ii) to evaluate the dissipation of fomesafen and thiamethoxam and their effect on three freshwater macrophytes in aquatic environments. Both LVAd and LVdf presented moderate sorption of fomesafen. Organic matter and pH played important role in sorption of fomesafen by these Latosols. Sewage sludge addition increased the rate of fomesafen dissipation in both Latosols, whereas phosphate had no effect on dissipation. Fomesafen did not cause injuries (carryover effect) to corn, based on plant dry weight at these experimental conditions. While phosphate and sewage sludge decreased leaching, adding vinasse to the LVAd increased leaching of fomesafen. Concentrations of thiamethoxam in the aquatic environment at all treatment levels decreased rapidly, with half-life values less than 5 days for all treatment concentrations. On the other hand, fomesafen had a slow rate of dissipation during the course of this study. The half-life of fomesafen in the water ranged between 42 and 80 days. As related to macrophyte response, there was no effect of fomesafen and thiamethoxam on Lemna minor and Elodea canadensis. However, at 35 and 49 days after treatment, there was a small trend towards increased wet and dry mass of the shoot and roots of M. spicatum, despite drastic declines in waterborne thiamethoxam concentrations. In contrast to thiamethoxam, wet and dry mass of shoot and roots of M. spicatum plants decreased significantly with increasing fomesafen concentration in the water.

ASSUNTO(S)

dissipação lixiviação carryover microcosmo ciencia do solo dissipation leaching microcosm

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