SIMULATION OF THE PERSISTENCE OF ATRAZINE IN SOIL AT DIFFERENT SITES IN PORTUGAL

The effects of soil temperature and soil moisture content on the rates of degradation of atrazine, were measured in the laboratory in soils from different sites in Portugal. Persistence of atrazine was measured in the same soils in the field during the spring and summer of 1984, 1985, 1986 and 1987. Weather records from the different sites, measured during the periods of the field experiments, were used in conjunction with appropriate constants derived from the laboratory data in a computer program to simulate persistence in the field. The model generally overestimated the observed soil residues, particularly during the first 7-14 days after application. The fit from the model was good from day 14 to the end of the experiments.