Effects of planting cover and sulfosulfuron application rates on its persistence in the soil of wheat fields

Sulfosulfuron as a very important member of sulfonylurea herbicides is able to control of wide range of grassy and broad-leaf weeds spectra in wheat. In order to study its persistence behavior in soil، an experiment was conducted with two factors included herbicide application dose (common and overdose) and planting cover (with natural stand covered and bare soil) in randomized completely block design with three replications. Soil samples were collected at predetermined intervals after herbicide application and residues of sulfosulfuron were analyzed by HPLC using photodiode array detector. The dissipation of sulfosulfuron was found to have first-order kinetics in soil but its degradation rate was not different in the natural stand covered soil than bare one in spite of application rates. Faster rates were observed in overdose than common application rate however it was not significantly different between them. The Half-time (t0. 5) of sulfosulfuron were 32. 8 and 23. 5 days in common and overdose in natural stand covered soil and 33. 8 and 25 days in bare soil respectively. These quantities for t0. 1 (90% reduction in initial herbicide concentration) were 109. 2 and 78. 1 days in natural stand covered and 112. 2 to 83. 2 days in bare one. Sulfosulfuron residue was detectable in 97 days after application at wheat harvest time.