title: Bromoxynil degradation in a Mississippi silt loam soil.
abstract: BACKGROUND
  The objectives of these laboratory experiments were: (1) to assess bromoxynil sorption, mineralization, bound residue formation and extractable residue persistence in a Dundee silt loam collected from 0-2 cm and 2-10 cm depths under continuous conventional tillage and no-tillage; (2) to assess the effects of autoclaving on bromoxynil mineralization and bound residue formation; (3) to determine the partitioning of non-extractable residues; and (4) to ascertain the effects of bromoxynil concentration on extractable and bound residues and metabolite formation.
  
  
  RESULTS
  Bromoxynil K(d) values ranged from 0.7 to 1.4 L kg(-1) and were positively correlated with soil organic carbon. Cumulative mineralization (38.5% +/- 1.5), bound residue formation (46.5% +/- 0.5) and persistence of extractable residues (T(1/2) < 1 day) in non-autoclaved soils were independent of tillage and depth. Autoclaving decreased mineralization and bound residue formation 257-fold and 6.0-fold respectively. Bromoxynil persistence in soil was rate independent (T(1/2) < 1 day), and the majority of non-extractable residues (87%) were associated with the humic acid fraction of soil organic matter.
  
  
  CONCLUSIONS
  Irrespective of tillage or depth, bromoxynil half-life in native soil is less than 1 day owing to rapid incorporation of the herbicide into non-extractable residues. Bound residue formation is governed principally by biochemical metabolite formation and primarily associated with soil humic acids that are moderately bioavailable for mineralization. These data indicate that the risk of off-site transport of bromoxynil residues is low owing to rapid incorporation into non-extractable residues.
authors.affiliation: USDA-Agricultural Research Service, Southern Weed Science Research Unit, Stoneville, MS 38776, USA. Robert.Zablotowicz@ars.usda.gov
authors.forename: Robert M
authors.initials: RM
authors.lastname: Zablotowicz
authors.forename: L Jason
authors.initials: LJ
authors.lastname: Krutz
authors.forename: Cesare
authors.initials: C
authors.lastname: Accinelli
authors.forename: Krishna N
authors.initials: KN
authors.lastname: Reddy
mesh_terms: D000327:Adsorption; D006540:Herbicides / Q000737:chemistry*; D008922:Mississippi; D009570:Nitriles / Q000737:chemistry*; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000737:chemistry
chemical_list: D006540:Herbicides; D009570:Nitriles; D012987:Soil; D012989:Soil Pollutants; C006826:bromoxynil