The sulfentrazone is regularly applied to sugarcane crop harvest residue forPRE control of weedy species, especially in the dry season during the year,but little is known about how rainfall timing or crop residue mass affectthe release of sulfentrazone into the soil and its subsequent effectiveness.Two experiments were conducted to examine the effects of sugarcane residuemass (5, 10, 15, and 20 t ha−1) and rainfall timing (1, 30, and60 d after herbicide application) on sulfentrazone retention. Rainfallvolumes were simulated at 2.5, 5, 10, 20, 35, 50, and 100 mm. A 20-mmrainfall volume was simulated at 7 and 14 d after the first simulated event.The water passing through the straw was collected after each rainfallsimulation. The concentration of sulfentrazone was measured by liquidchromatography and mass spectrometry. The initial 20 mm of rain released themaximum mass of sulfentrazone from the sugarcane residue. The mass ofsugarcane residue affected the amount of sulfentrazone recovered. The amountof sulfentrazone released from the residue was significantly reduced by thepersistence on the residue surface for long periods before the occurrence ofrain. During periods of low rainfall, recommendations for sulfentrazone ratemust take into account losses that occur when applied over the harvestresidues to design a weed-management plan that does not compromise efficacyand duration of the residual effects.