|Blanchard, Paul - MO DEPT OF CONSERVATION|
Submitted to: Symposium on the Fate and Chemistry of Modern Pesticides Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2004
Publication Date: August 16, 2004
Citation: Ghidey, F., Blanchard, P., Lerch, R.N., Kitchen, N.R., Alberts, E.E. 2004. Cropping system effects on herbicide transport to surface runoff from a claypan soil. I. Plot-scale analysis. In: Proceedings of the Symposium on the Fate and Chemistry of Modern Pesticide, August 16-19, 2004, Vail, CO.p. 57. Technical Abstract: Runoff-prone soils, such as those in the claypan soils region of Missouri and Illinois, have been shown to be particularly vulnerable to herbicide transport by surface runoff during the spring time. Seasonal losses as impacted by management practices are not well quantified for these soils. The effect of three cropping systems on herbicide loss in surface runoff was studied from 1997-2000 on claypan soil plots near Centralia, Missouri. Cropping System 1 (CS1) was a mulch tillage corn-soybean rotation system with herbicides surface applied then incorporated. Cropping System 2 (CS2) was a no-till corn-soybean rotation system with herbicide surface applied and not incorporated. Cropping System 5 (CS5) was a no-till corn-soybean-wheat rotation system with split herbicide application and no incorporation. The study was conducted on 0.34-ha plots equipped with H-flumes and automated samplers. During each runoff event, runoff volumes were measured, and water samples were collected at equal flow increments and analyzed for atrazine and metolachlor. Seasonal runoff and herbicide loads measured from cropping systems in no-till (CS2 and CS5) were significantly higher (p<0.1) than those under mulch tillage (CS1). Averaged over years, runoff measured from CS2 and CS5 was 20 and 24% higher than CS1. Atrazine losses from CS2 and CS5 were three to four times higher than that from CS1. Split herbicide application in CS5 resulted in much higher atrazine loss when compared to that from CS2. Approximately 0.8, 2.5, and 4.0% of the total atrazine applied was lost to surface runoff from CS1, CS2, and CS5, respectively. Metalochlor loss to surface runoff from CS1, CS2, and CS5 accounted for 1.1, 2.2, and 1.9% of the total applied, respectively. Atrazine and metolachlor concentrations from no-till (CS2 and CS5) were always higher than those from mulch tillage (CS1). Herbicide concentrations were extremely high in the first runoff event measured after application, particularly if it occurred soon after application. The trend in herbicide concentrations in runoff agreed well with the dissipation of herbicides measured in soil. In general, our study showed that the two main factors controlling herbicide transport were herbicide placement (i.e., incorporation vs. non-incorporated) and the timing of rainfall relative to application.