Outdoor lysimeter studies on 14C-Bentazone - results from different climatic sites

The fate of the 14C-labelled herbicide bentazone (Basagran(sup)R - 480 g AI/ha) was investigated in undisturbed sandy soil lysimeters exposed and cultivated under different climatic conditions. The lysimeters (1.2 m depth, 1 square meter Surface area) were taken from agricultural land and installed in outdoor testing facilities at the Fraunhofer-Institute in Schmallenberg and at the BASF AG, Limburgerhof. The formulated product was applied at both study sites post-emergence to cereals (1 kg AI/ha). Despite different climatic conditions and therefore varying amounts of leachate the total radioactivity in the leachate was very similar two years after a single application. A repeat application of 14C-bentazone in the second year led to an expected increase of total radioactivity in leachate. Nevertheless, the annual mean concentration of 14C-bentazone was still below 0.1 Myg/l. The relative amounts of total radioactivity in the soil cores two years after the second application were nearly identical (about 49% of the applied radioactivity) and corresponded approximately to the results obtained two years after the single application. No significant displacement of radioactive material into deeper soil layers was observed. 1-2% of the applied radioactive material was incorporated into the crop.