Adsorption and Desorption Characteristic of Metsulfuron-Methyl in Pakistani Soils

A sulfonylurea herbicide and Metsulfuron-Methyl (MM) were investigated for its sorption-desorption behavior on four Pakistani soils having different geographical conditions ranging from hilly areas to desert areas, by using batch equilibrium method. This sulfonylurea herbicide is used in Pakistan against a wide range of broad leaf weeds as well as some grasses. The data obtained in all tests showed that adsorption co-efficient isotherm for Metsulfuron-Methyl in four tested soil were well fitted the Freundlich equation. The isotherm was nonlinear in all cases with slope n<1 resembling the C-type curve. Distribution co-efficient (K-d) parameters are low i.e. 1.59 ml mu g(-1) indicating low adsorption. It was observed that MM herbicide showed a relatively greater degree of adsorption on soil samples that were collected from northern hilly areas Ayubia, Khyber Pukhtunkhwa (Silt loam) i.e. 25.5% and least adsorption on sandy Soil of Multan Punjab. Desorption percentage in four soils were found to be 61.06% to 70.70%. Soil organic matter (SOM) and pH were considered to be important factors leading to differences in sorption capacity and depended significantly on SOM.