Sorption and leaching of flucetosulfuron in soil

The adsorption-desorption and leaching of flucetosulfuron, a sulfonylurea herbicide, was investigated in three Indian soils. Freundlich adsorption isotherm described the sorption mechanism of herbicide with adsorption coefficients (K_f) ranging from 17.13 to 27.99 and followed the order: Clayey loam > Loam > Sandy loam. The K_f showed positive correlation with organic carbon (OC) (r = 0.910) and clay content (r = 0.746); but, negative correlation with soil pH (r = -0.635). The adsorption isotherms were S-type suggesting that herbicide adsorption was concentration dependent and increased with increase in concentration. Desorption followed the sequence: sandy loam > clayey loam > loam . Hysteresis (H) was observed in all the three soils with H < 1. Leaching of flucetosulfuron correlated positively with the soil pH; but, negatively with the OC content. Sandy loam soil (OC- 0.40%, pH -7.25) registered lowest adsorption and highest leaching of flucetosulfuron while lowest leaching was found in the loam soil (pH - 7.89, OC - 0.65%). The leaching losses of herbicide increased with increase in the rainfall intensity. This study suggested that the soil OC content, pH and clay content played important roles in deciding the adsorption-desorption and leaching behavior of flucetosulfuron in soils.