Enhanced degradation of metalaxyl in agricultural soils of São Paulo State, Brazil

Abstract

-This work investigated the effect of repeated applications on enhanced degradation of metalaxyl in two different agricultural soils used for cultivation of orange and lemon from Casa Branca and Itapetininga districts of São Paulo State, Brazil. Soil samples were collected from areas repeatedly treated with commercial ridomil 50GR for six successive years, and from other areas never exposed to this fungicide. At the laboratory, soil samples received a 14 C-metalaxyl solution and its degradation was studied through radiometric techniques to measure biomineralization and recovery of extractable-and soil-bound products. Enhanced degradation was verified only in one soil, although partial degradation and mineralization of the fungicide were detected in both soils. The different rates and patterns of metalaxyl degradation in the soils were probably due to their different physical, chemical, and biological characteristics.

Effect of formulation and repeated applications on the enantioselectivity of metalaxyl dissipation and leaching in soil

“…The form in which a pesticide is applied to soil and repeated pesticide applications to the same soil are agricultural practices that can greatly influence pesticide dissipation and leaching patterns. For example, accelerated degradation after repeated pesticide applications and reduced leaching by the use of clay‐based formulations, compared with formulations containing the pesticide in an immediately available form, have been described . For chiral pesticides, research conducted on this subject does not generally account for individual enantiomers, implicitly assuming that the effects of such practices are identical for both enantiomers …”