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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF ALTERNATIVE PRACTICES FOR IMPROVED WATERSHED MANAGEMENT Title: Herbicide Transport to Surface Runoff from a Claypan Soil: Scaling from Plots to Fields

Authors
item Ghidey, Fessehaie
item Baffaut, Claire
item Lerch, Robert
item Kitchen, Newell
item Sadler, Edward
item Sudduth, Kenneth

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2009
Publication Date: May 1, 2010
Citation: Ghidey, F., Baffaut, C., Lerch, R.N., Kitchen, N.R., Sadler, E.J., Sudduth, K.A. 2010. Herbicide Transport to Surface Runoff from a Claypan Soil: Scaling from Plots to Fields. Journal of Soil and Water Conservation. 65(3):168-179.

Interpretive Summary: Streams and drinking water reservoirs throughout the claypan soil region of Missouri and Illinois are particularly vulnerable to herbicide contamination from surface runoff because claypan soils have a high runoff potential. This study follows a large plot study conducted to quantify herbicide losses on claypan soils from a corn-soybean rotation under mulch and no-till tillage systems. The objectives of the present study were to confirm at field scale the plot scale results on the effects of tillage and herbicide incorporation on herbicide loads, to evaluate the effect of scaling from plot to field, and to test the previously developed plot-scale model with field data. Herbicide concentrations and loads in surface runoff were measured from two fields with cropping system similar to those in the plots. The percentage of applied atrazine and metolachlor lost in surface flow from the no-till field was between 2 and 3 times those from mulch tillage. Similar results were obtained at plot-scale study. The model developed from plot-scale data performed well at field scale for atrazine, but did not perform well for metolachlor. Model performance improved in calculating both atrazine and metolachlor when it was modified to include temperature. Overall, the study confirmed plot-scale results that atrazine losses were significantly higher when the herbicide was not incorporated. The study also showed that the model developed using plot-scale data was applicable in estimating atrazine concentrations at the field-scale. Implications include the need to incorporate atrazine on claypan soils when atrazine is an issue.

Technical Abstract: Streams and drinking water reservoirs throughout the claypan soil region of Missouri and Illinois are particularly vulnerable to herbicide contamination from surface runoff during the spring time period. This study follows a plot-scale study conducted on claypan soils to quantify herbicide losses from a corn-soybean rotation under mulch and no-till tillage systems. The objectives of the present study were to confirm at field scale the plot scale results on the effects of tillage and herbicide incorporation on herbicide transport, to evaluate the effect of scaling from plot to field, and to evaluate the applicability of plot-scale exponential models in calculating atrazine and metolachlor concentrations at the field scale. Herbicide transport to surface runoff was studied from two fields with cropping systems similar to those on the plots. Field 1 (F1) was a mulch tillage corn-soybean rotation system with herbicides surface applied then incorporated. Field 2 (F2) was a no-till corn-soybean rotation system with herbicide surface applied and not incorporated. The study was conducted from 1995-2001. During each event, runoff volumes were measured and water samples were collected at equal flow increments and analyzed for atrazine and metolachlor concentrations. The percentages of applied atrazine and metolachlor transported to surface runoff from the no-till field (F2) were 2.8 and 2.0 times those from mulch tillage (F1), respectively. Although, the percent of applied atrazine and metolachlor transported to surface runoff from the plots was 1.9 and 2.8 times that from F1, the difference was not statistically significant because of low number of data points. The exponential model that predicts herbicide concentrations as a function of application rate, runoff volume, and days after application developed from plot-scale data performed well in calculating field atrazine concentrations from both mulch and no-till systems with r2 = 0.71 and Nash and Suttcliffe efficiency (Ens) = 0.66. However, model performance in calculating metolachlor concentrations was poor. When the model was modified to use the parameter cumulative temperature instead of days after application, it improved model performance in calculating atrazine and metolachlor concentrations, particularly at field scale. Overall, the study confirmed plot-scale results that atrazine concentrations and losses were significantly higher for a no-till system than for a mulch tillage system in which the herbicide was incorporated. The study also showed that the model developed using plot-scale data was applicable in calculating concentrations at the field-scale, particularly for atrazine.

Last Modified: 10/21/2014
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