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This article in JEQ

  1. Vol. 37 No. 6, p. 2212-2220
    Received: Oct 28, 2007

    * Corresponding author(s): Melissa.Bridges@colostate.edu
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Spatial Variability of Atrazine and Metolachlor Dissipation on Dryland No-tillage Crop Fields in Colorado

  1. Melissa Bridges *a,
  2. W. Brien Henryb,
  3. Dale L. Shanerc,
  4. R. Khoslad,
  5. Phil Westrae and
  6. Robin Reichf
  1. a Dep. of Bioagricultural Sciences and Pest Management, Campus Delivery 1179, Colorado State Univ., Fort Collins, CO 80523-1179
    b USDA-ARS, Corn Host Plant Resistance Research Unit, Dorman Hall, Box 9555, Mississippi State, MS 39762
    c USDA-ARS, Water Management Research Unit, 2150 Centre Ave., Building D, Suite 320, Fort Collins, CO 80526
    d Soil and Crop Sciences Dep., C-13 Plant Science Building, Colorado State Univ., Fort Collins, CO 80523-1170
    e Dep. of Bioagricultural Sciences and Pest Management, Weed Research Lab 112, Colorado State Univ., Fort Collins, CO 80523-1177
    f Dep. of Forest, Rangeland and Watershed Stewardship, 130 Forestry Bldg., Colorado State Univ., Fort Collins, CO 80523-1472


An area of interest in precision farming is variable-rate application of herbicides to optimize herbicide use efficiency and minimize negative off-site and non-target effects. Site-specific weed management based on field scale management zones derived from soil characteristics known to affect soil-applied herbicide efficacy could alleviate challenges posed by post-emergence precision weed management. Two commonly used soil-applied herbicides in dryland corn (Zea mays L.) production are atrazine and metolachlor. Accelerated dissipation of atrazine has been discovered recently in irrigated corn fields in eastern Colorado. The objectives of this study were (i) to compare the rates of dissipation of atrazine and metolachlor across different soil zones from three dryland no-tillage fields under laboratory incubation conditions and (ii) to determine if rapid dissipation of atrazine and/or metolachlor occurred in dryland soils. Herbicide dissipation was evaluated at time points between 0 and 35 d after soil treatment using a toluene extraction procedure with GC/MS analysis. Differential rates of atrazine and metolachlor dissipation occurred between two soil zones on two of three fields evaluated. Accelerated atrazine dissipation occurred in soil from all fields of this study, with half-lives ranging from 1.8 to 3.2 d in the laboratory. The rapid atrazine dissipation rates were likely attributed to the history of atrazine use on all fields investigated in this study. Metolachlor dissipation was not considered accelerated and exhibited half-lives ranging from 9.0 to 10.7 d in the laboratory.

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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