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

Abstract

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. Desethyl atrazine [6-chloro-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine] comprised 7 to 39% of the total triazine loss.

Demonstrating an approach for including pesticide use in life-cycle assessment: Estimating human and ecosystem toxicity of pesticide use in Midwest corn farming

“…The difference is likely due to the inclusion of substance dispersion by wind drift, which is not considered in the previously reported emission factor (USEPA 1994). Water releases from atrazine and metolachlor use in the Midwest were reported previously (Ng et al 1995;Gaynor et al 2001) based on multiple field and modeling studies, which found 2.5-15 % of atrazine and metolachlor applied together in the Midwest was discharged into the combined runoff. This overlaps with our results for atrazine and S-metolachlor of 1.4-16 %.…”

“…However, considering the uncertainty of toxicity estimates in impact assessment tools, PestLCI is appropriate for estimating release inventories and represents a significant improvement over static emission factors. In addition, we verified our estimates of pesticide releases through comparison with data sets published by EPA and peer-reviewed studies (USEPA 1994;Ng et al 1995;Gaynor et al 2001). The user should be aware that the analysis represents pesticide use for corn farming in 2006, and appropriate modifications and validation are required for other years.…”

Tillage management effects on pesticide fate in soils. A review

“…No difference between tillage systems was found but runoff losses were positively correlated with the half-lives of the molecules. In other studies, water solubility directly determines the loss by runoff and explains differences in behaviour between alachlor and cyanazine (Hansen et al, 2001) or between atrazine and metribuzin (Gaynor et al, 2001). Isoxaflutole has a low solubility in water but its hydrolysis forms a diketonitrile metabolite (active ingredient) which is 50 times more soluble and thus transported by runoff (Rector et al, 2003).…”

Review of Pesticide Retention Processes Occurring in Buffer Strips Receiving Agricultural Runoff1

“…, 1983, 1991; Glenn and Angle, 1987; Paterson and Schnoor, 1992; Shipitalo et al. , 1997; Gaynor et al. , 2001).…”