Paclobutrazol transport in soil columns.
Milfont M. L., Antonino A. C. D., Martins J. M. F., Netto A. M., Gouveia E. R., Correa M. M.
Author Affiliation: Departamento de Energia Nuclear, DEN-CTG-UFPE. Av. Prof. Luiz Freire 1000 - Cid. Universitária, CEP 50740-540 Recife, PE, Brazil.
Revista Brasileira de Ciência do Solo 32 : 2165-2175
Abstract : This study investigated the mechanisms involved in the transport and sorption of paclobutrazol (PBZ) in an Ultisol and a Vertisol, both of the São Francisco Valley, Brazil. Column breakthrough experiments were performed with a water tracer (bromide) and with PBZ at 0.4 and 1.6 cm3/minute in the two soils. Hydrodispersive parameters of both soils were obtained by fitting the tracer breakthrough curves (BTC) with the convection-dispersion (CDE) model, whereas the parameters of PBZ reactive transport were obtained with the CDE-2 sorption sites model, through the CXTFIT code. PBZ presents a lower retardation factor in the Vertisol than in the Ultisol. The water flow significantly affected PBZ mass balance, mainly because of sorption/desorption hysteresis, suggesting partial irreversible sorption of the chemical. The two sites model fitted well the tracer and PBZ breakthrough curves. The results showed that PBZ transport is significantly influenced by its interactions with the soil matrix through rate-limited sorption. The determined transport parameters indicated that PBZ applied to the two tropical soils cultivated with mango presents an important leaching potential and contamination risk of the groundwater of the São Francisco Valley.