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This article in JEQ

  1. Vol. 37 No. 1, p. 90-97
     
    Received: Apr 30, 2007


    * Corresponding author(s): jean.martins@hmg.inpg.fr
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doi:10.2134/jeq2007.0210

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

  1. Mônica Lúcia Milfonta,
  2. Jean Manuel Fonseca Martins *b,
  3. Antonio Celso Dantas Antoninoa,
  4. Ester Ribeiro Gouveiac,
  5. André Maciel Nettoa,
  6. Véronique Guinéb,
  7. Hélène Masb and
  8. Maria Betânia Galvão dos Santos Freired
  1. a Universidade Federal de Pernambuco, Departamento de Energia Nuclear, Av. Prof. Luiz Freire 1000, Cid. Universitária, CEP 54740-540, Recife, PE, Brazil
    b Laboratoire d'étude de Transferts en Hydrologie et Environnement (LTHE), Univ. Grenoble I, CNRS, BP 53, 38041, Grenoble Cedex 09, França
    c Universidade Federal de Pernambuco, Departamento de Antibióticos, Av. Prof. Arthur de Sá, Cid. Universitária, Recife, PE, Brazil
    d Universidade Federal Rural de Pernambuco, Departamento de Agronomia, Rua Dom Manoel de Medeiros, s/n, Dois Irmãos, CEP 52171-900, Recife, PE, Brazil

Abstract

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 (dS t dt =k2(S e 2−S t )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 K OC values were 1275 ± 34 (logK OC = 3.11) and 1156 ± 49 (logK OC = 3.06) L kg−1, respectively. Considering the very different texture of the two soils and the similar K OC 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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Copyright © 2008. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America