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