Evolution of soil biological properties after addition of glyphosate, diflufenican and glyphosate+diflufenican herbicides

The aim of this paper was to study in laboratory the degradation and the effects on biological properties in two soils after the addition of glyphosate, diflufenican and glyphosate+diflufenican. One hundred grams of sieved soil (<2 mm) were mixed with (i) 13 mL of Zarpa® (16% glyphosate and 4% diflufenican) prepared in a water solution of 1 L (0.52 g of glyphosate and 2.08 g of diflufenican), (ii) 5.2 mL of Round up® (40% glyphosate), prepared in a water solution of 1 L (0.52 g of glyphosate), and (iii) 1.19 mL of Brodal® (43.5% diflufenican), prepared in a water solution of 1 L (2.08 g of diflufenican). Soil samples were collected after 0, 1, 5, 10, 15, 30, 60, 120 and 180 d of incubation and analyzed for microbial biomass-C and dehydrogenase, urease, β-glucosidase, phosphatase, arylsulphatase activities and glyphosate and diflufenican contents. At the end of the experiment, in the clayey texture soil the glyphosate and diflufenican contents were higher 50% and 30.7%, respectively, for the glyphosate+diflufenican treatment compared to glyphosate and diflufenican treatments, respectively. In the sandy loam texture soil the glyphosate and diflufenican contents were higher (38.9% and 39.4%, respectively) when the glyphosate and diflufenican were added as Zarpa® than Round up® or Brodal®. The application of glyphosate+diflufenican mixture to soil increased the toxic effects of both herbicides in the soil biological activity and the individual soil persistence of each herbicide.