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TECHNICAL REPORT
SURFACE WATER QUALITY

Tillage, Intercrop, and Controlled Drainage–Subirrigation Influence Atrazine, Metribuzin, and Metolachlor Loss

^a Crops Research Centre, Agriculture and Agri-Food Canada, Harrow, ON N0R 1G0
^b NWRI Environment Canada, Burlington, ON L7R 4A6
^c Dow AgroSciences, Environmental Fate, Bldg 306-Az, 9330 Zionsville Rd., Indianapolis, IN 46268

Corresponding author (gaynorj{at}em.agr.ca)

Received for publication April 7, 2000. Atrazine (6-chloro-N²-ethyl-N⁴-isopropyl-1,3,5-triazine-2,4-diamine) and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] have been found with increasing occurrence in rivers and streams. Their continued use will require changes in agricultural practices. We compared water quality from four crop-tillage treatments: (i) conventional moldboard plow (MB), (ii) MB with ryegrass (Lolium multiflorum Lam.) intercrop (IC), (iii) soil saver (SS), and (iv) SS + IC; and two drainage control treatments, drained (D) and controlled drainage–subirrigation (CDS). Atrazine (1.1 kg a.i. ha^-1), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one] (0.5 kg a.i. ha^-1), and metolachlor (1.68 kg a.i. ha^-1) were applied preemergence in a band over seeded corn (Zea mays L.) rows. Herbicide concentration and losses were monitored from 1992 to spring 1995. Annual herbicide losses ranged from <0.3 to 2.7% of application. Crop-tillage treatment influenced herbicide loss in 1992 but not in 1993 or 1994, whereas CDS affected partitioning of losses in most years. In 1992, SS + IC reduced herbicide loss in tile drains and surface runoff by 46 to 49% compared with MB. The intercrop reduced surface runoff, which reduced herbicide transport. Controlled drainage–subirrigation increased herbicide loss in surface runoff but decreased loss through tile drainage so that total herbicide loss did not differ between drainage treatments. Des-ethyl atrazine [6-chloro-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine] comprised 7 to 39% of the total triazine loss.

Abbreviations: CDS, controlled drainage–subirrigation • D, drained • DAA, days after application • IMAC, interim maximum acceptable concentration • MB, moldboard plow • MB + IC, moldboard plow with ryegrass intercrop • SS, soil saver • SS + IC, soil saver with ryegrass intercrop

This article has been cited by other articles:

				M. B. David, L. E. Gentry, K. M. Starks, and R. A. Cooke Stream Transport of Herbicides and Metabolites in a Tile-Drained, Agricultural Watershed J. Environ. Qual., September 1, 2003; 32(5): 1790 - 1801. [Abstract] [Full Text] [PDF]

				J.D. Gaynor, C.S. Tan, C.F. Drury, T.W. Welacky, H.Y.F. Ng, and W.D. Reynolds Runoff and Drainage Losses of Atrazine, Metribuzin, and Metolachlor in Three Water Management Systems J. Environ. Qual., January 1, 2002; 31(1): 300 - 308. [Abstract] [Full Text] [PDF]