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This article in JEQ

  1. Vol. 31 No. 1, p. 300-308
    Received: Jan 22, 2001

    * Corresponding author(s): gaynorj@em.agr.ca
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Runoff and Drainage Losses of Atrazine, Metribuzin, and Metolachlor in Three Water Management Systems

  1. J.D. Gaynor *a,
  2. C.S. Tana,
  3. C.F. Drurya,
  4. T.W. Welackya,
  5. H.Y.F. Ngab and
  6. W.D. Reynoldsa
  1. a Crops Research Centre, Agriculture and Agri-Food Canada, 2585 County Road E, Harrow, ON, N0R 1G0 Canada
    b National Water Research Institute, Environment Canada, Burlington, ON, L7R 4A6 Canada


Rainfall can transport herbicides from agricultural land to surface waters, where they become an environmental concern. Tile drainage can benefit crop production by removing excess soil water but tile drainage may also aggravate herbicide and nutrient movement into surface waters. Water management of tile drains after planting may reduce tile drainage and thereby reduce herbicide losses to surface water. To test this hypothesis we calculated the loss of three herbicides from a field with three water management systems: free drainage (D), controlled drainage (CD), and controlled drainage with subsurface irrigation (CDS). The effect of water management systems on the dissipation of atrazine (6-chloro-N 2-ethyl-N 4-isopropyl-1,3,5-triazine-2,4-diamine), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one), and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] in soil was also monitored. Less herbicide was lost by surface runoff from the D and CD treatments than from CDS. The CDS treatment increased surface runoff, which transported more herbicide than that from D or CD treatments. In one year, the time for metribuzin residue to dissipate to half its initial value was shorter for CDS (33 d) than for D (43 d) and CD (46 d). The half-life of atrazine and metolachlor were not affected by water management. Controlled drainage with subsurface irrigation may increase herbicide loss through increased surface runoff when excessive rain is received soon after herbicide application. However, increasing soil water content in CDS may decrease herbicide persistence, resulting in less residual herbicide available for aqueous transport.

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Copyright © 2002. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.31:300–308.