Lysimeter study of imidacloprid after seed treatment of sugar beet in two crop rotations

According to German Lysimeter Guideline the leaching behavior of [imidazoli dine-4,5-C-14] imidacloprid (insecticide) and its degradation products is i nvestigated under practice-relevant field conditions. Imidacloprid treated sugar beet seed was sown in two undisturbed soil monoliths (1.0 m(2) surfac e area, 1.1 m depth) of sandy loam on April 1991 and 1994. The application rate was 1.3 mg active ingredient/pellet (9 pellet/m(2)) corresponding to a bout 120 g/hectare each. In the other years cereals were grown. Data/result s were gathered during the five years on 1) weather, 2) occurance, volumes, radioactive residues of leachate, 3) yields, residues in the harvested cro ps, 4) distribution of residues in the soil monoliths at the end of the stu dy, 5) material balance and calculation of portion mineralized to (CO2)-C-1 4. This study confirms the low mobility of imidacloprid and its degradation products in soil under practice-relevant field conditions. Following the u se of imidacloprid in the recommended manner the possibility of contaminati on of deeper soil layers and groundwater can be excluded.