Under aerobic conditions, a slow degradation of butralin has been observed in a sandy loam soil at 25° C. The phenyl ring was poorly mineralized with 0.6% of the applied dose appearing as 14CO2 following 12 months of incubation. Bound residue was 9.8 % after 3 months and 11 % after 12 months. The major degradation product detected in soil was 4-tert-butyl-2,6-dinitroaniline (DNTBA) which reached approximately 2.1% of the applied dose at the conclusion of the incubation period. Up to 14.6 % of the applied butralin volatilized from soil within 12 months. The dissipation half-life, extrapolated from the butralin values in soil under experimental conditions of 25°C and 75% WHC, was calculated to be 1 126 days by the notifier. The RMS recalculated the DT50 value using a first order exponential regression, and re-incorporating the volatilized butralin in order to consider true degradation of butralin and not the conjugated action of degradation and volatilization. The DT50 was found to be 1949 days. Since this half-life greatly exceeds the study duration of 12 months, its absolute value is indicative only of relative persistence under these experimental conditions.