Parameter estimation using pesticide degradation experiments under varyingsoil temperatures and soil water contents

One of the major problems in the assessment of the environmental fate of a pesticide is the transfer of laboratory experiments to field conditions. A new experimental design was developed to establish a link between laborator y and field studies. The degradation of metazachlor was studied in sieved s oil under constant incubation conditions. Further experiments were conducte d to measure the effect of controlled varying temperatures and soil water c ontents. Both studies were used to estimate model parameters. The predictio ns were compared with measurements from a field study. Model parameters wer e estimated from the field experiment by using 'inverse modelling' techniqu e. The dissipation of the herbicide under outdoor conditions could be simul ated well with parameters obtained from studies under constant conditions. It was possible to estimate reliable parameters using the result of the deg radation studies under varying incubation conditions. The advantages and pr oblems using the inverse modelling technique are discussed.