Lysimeter experiments on bentazon

The leaching behaviour, distribution, and metabolism of the herbicide bentazon within two years following application was investigated by a lysimeter study with undisturbed soil monolith and using the radiolabelled compound. This was achieved by analyzing compounds appearing in the leachate as well as analyzing radiolabelled residues distribution in the 1 m soil profile and in plants. Within the two years study less than 4 % of the applied amount of radioactive material occured in the leachate. The leached material, however, contained only minor amounts of bentazon. 0.03 % of the applied active ingredient reached the level below 1 meter. Only minor amounts of bentazon could be detected in the different soil layers two years after application, thus bentazon does not tend to accumulate in soil and does not move to deeper soil zones or groundwater. The uptake by plants amounted to 0.9% of the originally applied active ingredient. Approximately 50 % of the applied radioactive material had left the system within the two years. These losses might account for volatilization and/or mineralization processes.