Oxadiazon residues in the soil surface collected from Rose Garden were observed in January 2005 (Table 2) with relative concentrations of 0.31 and 0.33% of the total soil extracts in January and February 2005, respectively. After 2 months, the dissipation level of oxadiazon residues started to increase due to the soil factors such as soil moisture and temperature (Chakraborty et al. 1999; Barrett and Lavy 1984). The residue level of oxadiazon was decreased to about four times in all the samples starting in March 2005 until May 2005 (Table 2).