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Reactivity of the Plant Growth Regulator Paclobutrazol (Cultar) with Two Tropical Soils of the Northeast Semiarid Region of Brazil

Abstract : Received for publication April 30, 2007. The reactivity of paclobutrazol (PBZ, a plant growth retardant) with a Yellow Ultisol and a Vertisol from the semiarid northeast region of Brazil was evaluated through batch sorption experiments and modeling. Although not instantaneous, the sorption kinetic of PBZ (pure and formulated) was fast (a few hours) in both soils. The sorption kinetics were well described by a second-order (Formula=k2(Se2–St)2) but not by a first-order model. The sorption isotherms were found to be linear and the calculated KD values were 8.8 ± 0.11 and 7.4 ± 0.2 L kg–1 for pure PBZ in the Ultisol and the Vertisol, respectively. The corresponding KOC values were 1275 ± 34 (logKOC = 3.11) and 1156 ± 49 (logKOC = 3.06) L kg–1, respectively. Considering the very different texture of the two soils and the similar KOC values determined, these results showed that in both soils, the sorption of PBZ is dominantly controlled by organic matter, although some interactions of PBZ with iron oxides (goethite) were observed in the Ultisol. Based on these sorption parameters a low leachability potential of PBZ in soils is anticipated, as they correspond to a groundwater ubiquity score (GUS) ranging from 2.0 to 2.7, i.e., moderately to not mobile, in contradiction with the actual groundwater situation in Brazil. This work stresses the need to evaluate and predict the risk associated with aquifer contamination by this widely used plant growth regulator.
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https://hal-insu.archives-ouvertes.fr/insu-00389046
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Submitted on : Thursday, May 28, 2009 - 9:42:39 AM
Last modification on : Friday, September 25, 2020 - 11:02:44 AM

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Monica Lucia Milfont, Jean Martins, Antonio Celso Dantas Antonino, Ester Ribeiro Gouveia, Andre Maciel Netto, et al.. Reactivity of the Plant Growth Regulator Paclobutrazol (Cultar) with Two Tropical Soils of the Northeast Semiarid Region of Brazil. Journal of Environmental Quality, Crop Science Society of America, 2008, 37 (1), pp.90 à 97. ⟨10.2134/jeq2007.0210⟩. ⟨insu-00389046⟩

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