Sorption of Paclobutrazol in two soils of irrigated mango orchards

Abstract

The sorption kinetics and isotherm of Paclobutrazol (PBZ) were determined in two soils from irrigated mango (Mangifera indica L. cv. Tommy Atkins)  orchards with no recorded use of PBZ. An Argisol and a Vertisol respectively from Bebedouro and Mandacaru Experimental Stations of the Brazilian Organization for Agriculture and Animal Research (EMBRAPA Semi-Arid) collected in the Municipalities of Petrolina, PE, and Juazeiro, BA were used. The experiments were carried out in laboratory conditions at 25°C and PBZ concentration was determined by high performance liquid chromatography (HPLC). For both soils, the PBZ kinetic sorption was fast and best described by a second order model and the isotherms sorption were linear. The values of KD and KOC were 8.8 and 7.4 cm³ g^-1 and 1275 (log(Koc) = 3.11) and 1156 (log(Koc) = 3.06) cm³ g^-1, for the Argisol and the Vertisol, respectively. These results show that for both soils, the reactivity of PBZ with organic matter is predominant in determining the sorption, although some interaction of PBZ with iron oxides (goethite) can take place in the Argisol.