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Journal of Environmental Quality Abstract - Special Submissions: Agricultural Air Quality

Comparison of Field-scale Herbicide Runoff and Volatilization Losses: An Eight-Year Field Investigation


This article in JEQ

  1. Vol. 40 No. 5, p. 1432-1442
    Received: Mar 4, 2011

    * Corresponding author(s): timothy.gish@ars.usda.gov
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  1. Timothy J. Gish *a,
  2. John H. Pruegerb,
  3. Craig S.T. Daughtryc,
  4. William P. Kustasd,
  5. Lynn G. McKeee,
  6. Andrew L. Russf and
  7. Jerry L. Hatfieldg
  1. a USDA–ARS Hydrology and Remote Sensing Laboratory, Beltsville, MD
    b USDA–ARS National Laboratory for Agriculture and the Environment, Ames, IA
    c Daughtry, Hydrology and Remote Sensing Laboratory, Beltsville, MD
    d USDA–ARS Hydrology and Remote Sensing Laboratory, Beltsville, MD
    e USDA–ARS Hydrology and Remote Sensing Laboratory, Beltsville, MD
    f Hydrology and Remote Sensing Laboratory, Beltsville, MD; and
    g USDA–ARS National Laboratory for Agriculture and the Environment, Ames, IA. Trade names are for the benefit of the reader and imply no endorsement by USDA. Assigned to Associate Editor Sharon Papiernik


An 8-yr study was conducted to better understand factors influencing year-to-year variability in field-scale herbicide volatilization and surface runoff losses. The 21-ha research site is located at the USDA–ARS Beltsville Agricultural Research Center in Beltsville, MD. Site location, herbicide formulations, and agricultural management practices remained unchanged throughout the duration of the study. Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] and atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] were coapplied as a surface broadcast spray. Herbicide runoff was monitored from a month before application through harvest. A flux gradient technique was used to compute volatilization fluxes for the first 5 d after application using herbicide concentration profiles and turbulent fluxes of heat and water vapor as determined from eddy covariance measurements. Results demonstrated that volatilization losses for these two herbicides were significantly greater than runoff losses (P < 0.007), even though both have relatively low vapor pressures. The largest annual runoff loss for metolachlor never exceeded 2.5%, whereas atrazine runoff never exceeded 3% of that applied. On the other hand, herbicide cumulative volatilization losses after 5 d ranged from about 5 to 63% of that applied for metolachlor and about 2 to 12% of that applied for atrazine. Additionally, daytime herbicide volatilization losses were significantly greater than nighttime vapor losses (P < 0.05). This research confirmed that vapor losses for some commonly used herbicides frequently exceeds runoff losses and herbicide vapor losses on the same site and with the same management practices can vary significantly year to year depending on local environmental conditions.

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