Adsorption and Desorption of DTP, the Herbicidal Entity of Pyrazolate, by Soils and Vertical Mobility of Pyrazolate and DTP in Paddy Fields

Abstract

The adsorption-desorption of DTP [4-(2, 4-dichlorobenzoyl)-1, 3-dimethyl-5-hydroxypyrazole], a hydrolysate and herbicidal entity of pyrazolate, was studied with various types of soil. The adsorption isotherms of DTP fitted the empirical Freundlich equation. Although distribution coefficients (Kd) of DTP significantly varied among the test soils, the soils had a great adsorptive capacity for DTP. Most of DTP adsorbed by the soils was gradually and steadily desorbed into water. In paddy fields where a granular formulation of 10% pyrazolate was applied, both pyrazolate and DTP, forming a treatment layer at the soil surface, were hardly mobile by leaching and gradually dissipated through biodegradation.