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This article in JEQ

  1. Vol. 14 No. 4, p. 585-592
     
    Published: Oct, 1985


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doi:10.2134/jeq1985.00472425001400040023x

Picloram Movement in an Appalachian Hardwood Forest Watershed1

  1. D. G. Neary,
  2. P. B. Bush,
  3. J. E. Douglass and
  4. R. L. Todd2

Abstract

Abstract

Picloram (4-amino-3,5,6-trichloropicolinic acid) was applied at a rate of 5.0 kg ha−1 acid equivalent to 4 ha of the 28-ha Watershed 19, Coweeta Hydrologic Laboratory in western North Carolina. The herbicide was broadcast manually as a pellet formulation (10% acid equivalent) in May 1978. The objective was to eliminate a poor-quality mixed oak overstory and rhododendron (Rhododendron maximum L.)-laurel (Kalmia latifolia L.) understory prior to planting white pine (Pinus strobus L.). Picloram residues in samples from an Umbric Dystrochrept soil peaked in concentration in the upper 0.07 m at 11.58 mg kg−1, had a half-life of about 4 weeks, and declined to near detection limits 28 weeks after application. Soil solution contained the highest picloram levels at 0.6 m (peak of 350 mg m−3). Picloram residues were detected in soil solution 1.2 m into the soil, but concentrations were < 25 mg m−3, and persisted for only 60 weeks. Intensive sampling of two springs detected trace levels for a period of 18 d. Only sporadic, low-level picloram residues were detected in streamflow from nested 10-ha and 28-ha watersheds during a 70-week period. Use of the herbicide picloram did not affect the quality of streamflow from Watershed 19 for domestic or agricultural purposes.

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