AVAILABILITY AND PERSISTENCE OF ISOPROTURON UNDER FIELD AND LABORATORY CONDITIONS

Field and laboratory tests were conducted to investigate the disappear ance and decrease in availability of the herbicide isoproturon in soil with time. Monitoring the fate of C-14-labeled isoproturon gave the p ersistence of the herbicide under different conditions. The calculated half-life (DT50) of the extractable parent product was close to 19 da ys for the two experiments, whereas half-lives of exhaustive extractab le C-14-residues averaged 22 days under controlled conditions versus 4 8 days in the field. Moreover, if nonextractable C-14-residues were ta ken into account in estimating isoproturon fate, the DT50 of radioacti ve residues in soil (extractable parent and degradation products + non extractable residues) reached 1 to 1.4 years under field and controlle d conditions, respectively. The variability of disappearance rates for the different kinds of residues is discussed within a wider definitio n of persistence. (C) 1996 Academic Press.