Columbia, Missouri. Contents

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1 Supplemental Material to Accompany: Long-term Agro-ecosystem Research in the Central Mississippi River Basin, USA - SWAT Simulation of Flow and Water Quality in the Goodwater Creek Experimental Watershed Claire Baffaut 1, Fessehaie Ghidey 1, E. John Sadler 1, and Stephen H. Anderson 2 1 USDA-ARS Cropping Systems and Water Quality Research Unit 2 University of Missouri, Department of Soil, Environmental and Atmospheric Sciences Columbia, Missouri Contents S1. Field operation scenarios... 2 S2. Land use and land management distribution... 4 S3. SWAT sensitive parameters in GCEW... 5 S4. Simulated effects of operation scheduling... 6 S5. Simulated effectiveness of herbicide incorporation... 7 S6. Simulated effectiveness of reducing atrazine application rate... 8 S7. References... 8 Tables: Supplemental Table S1. Crop and tillage management for corn, grain sorghum, soybean, and winter wheat Supplemental Table S2. Land use and land management distribution before and after Hydrologic Response Unit definition Supplemental Table S3: SWAT model parameters identified as sensitive and adjusted during calibration Supplemental Table S4. Effect of using planting progress reports on simulated annual atrazine and sediment export from GCEW Supplemental Table S5. Effect of incorporation after application on simulated annual atrazine export from GCEW Supplemental Table S6. Effect of atrazine application rates on simulated atrazine export from GCEW.... 8

2 S1. Field operation scenarios Field operation scenarios were derived from producer specific information obtained through surveys conducted in 1992 and 2007, along with information on agronomic rates of fertilizers corresponding to expected crop yields in the region and label rates for herbicides. Dates were initially defined. Heat unit indices are defined in two ways, depending upon the growing status of a crop. If a crop is not growing, the heat unit index is defined as the fraction of cumulative heat degree days since the beginning of the year by the average annual number of heat degree days, relative to a base temperature of 0 o C. If a crop is growing, the heat unit index is defined as the fraction of cumulative heat degree days since the beginning of the growing season by the total number of heat degree days needed to bring the plant to maturity, relative to the base temperature of the plant. Supplemental Table S1. Crop and tillage management for corn, grain sorghum, soybean, and winter wheat. Crop Type Management Date HUI 1 Corn Conventional Corn Conservation Corn no-till Sorghum Conventional Disking Injection of Anhydrous 130 kg ha -1 Spreading of Elemental 33.6 kg ha -1 Spreading of Elemental 24.3 kg ha -1 Field Cultivation Planting corn Atrazine broadcast 2.25 kg ha -1 Harvest / Kill Generic Conservation Tillage Injection of Anhydrous 130 kg ha -1 Spreading of Elemental 33.6 kg ha -1 Spreading of Elemental 39.4 kg ha -1 Generic Conservation Cultivation Planting corn Atrazine broadcast 2.25 kg ha -1 Harvest / Kill Knifing of Anhydrous 130 kg ha -1 Spreading of Elemental 33.6 kg ha -1 Spreading of Elemental 24.3 kg ha -1 Atrazine broadcast 1.25 kg ha -1 No-till mixing Planting corn Atrazine broadcast 1.25 kg ha -1 Harvest Disking Injection of Anhydrous 130 kg ha -1 Spreading of Elemental 33.6 kg ha -1 Spreading of Elemental 39.4 kg ha -1 Field Cultivation Planting sorghum Atrazine broadcast 2.25 kg ha -1 Harvest / Kill Nov 1 March 15 April 1 April 2 April 3 April 25 May 8 Oct 1 Nov 1 March 15 April 1 April 2 April3 April 25 May 8 Oct 1 March 25 April 8 April 9 April 10 April 11 May 5 May 16 Oct 10 Nov 1 March 15 April 1 April 2 April3 April 25 May 8 Oct Soybean General Conservation Plowing Nov

3 Crop Type Management Date HUI 1 Conservation Spreading of Elemental 15.1 kg ha -1 Generic Conservation Cultivation Planting soybeans Harvest / Kill May 1 May 2 May 5 Oct Soybean no-till Wheat no-till 1 Heat Unit Index Spreading of Elemental 15.1 kg ha -1 No-till incorporation Planting soybeans Harvest Spreading of Elemental 44.8 kg ha -1 Spreading of Elemental 30 kg ha -1 No-till incorporation Planting wheat Spreading of Elemental 67.2 kg ha -1 Harvest / Kill wheat Planting soybean Harvest / Kill soybean May 9 May 10 May 12 Oct 1 Oct 12 Oct 13 Oct 14 Oct 15 March 15 June 25 July 3 Oct

4 S2. Land use and land management distribution Supplemental Table S2. Land use and land management distribution before and after Hydrologic Response Unit definition. Land Use % of watershed area before HRU definition % of watershed area after HRU definition Residential Corn Conventional Corn Conservation Corn No-till Soybean Conventional Soybean Conservation Soybean No-till Grain Sorghum Conventional Wheat No-till Woodland - Grazed Woodland - Non grazed Hay Pasture Pasture CRP Water

5 S3. SWAT sensitive parameters in GCEW Supplemental Table S3: SWAT model parameters identified as sensitive and adjusted during calibration. Model output Stream Flow Sediment Yield Atrazine Load P transport Parameter Definition Default Value Baseline Value Adjusted Value SFTMP Snow fall temperature SMTMP Snow melt temperature SMFMX Snow melt max rate SMFMN Snow melt min rate TIMP Snow pack temperature lag factor SNOCOVMX Minimum snow water content for 100% snow cover Fraction of snow volume represented by SNCSOCOV SNOCOVMX that corresponds to 50% snow cover ESCO Soil evaporation compensation factor EPCO Plant evaporation compensation factor SURLAG Surface runoff lag coefficient SHALLST Initial depth of water in the shallow aquifer DEEPST Initial depth of water in the deep aquifer GW_DELAY Groundwater delay time ALPHA_BF Baseflow alpha factor GWQMN Shallow aquifer depth of water required for return flow to occur GW_REVAP Groundwater revap coeffcient REVAPMN Shallow aquifer depth of water required for revap to occur RCHRG_DP Deep aquifer percolation fraction USLE_P USLE support practice factor USLE_K USLE erodibility factor USLE_C Minimum value of USLE crop factor SWAT database Adjusted by tillage according to the values given by Alberts et al. (1985) CH_COV1 Channel erodibility factor CH_COV2 Channel cover factor ADJ_PKR Peak rate adjustment factor PRF Peak rate adjustment factor for sediment routing SPCON Linear parameter for channel sediment routing SPEXP Exponent parameter for channel sediment routing HLIFE_S Atrazine half life PERCOP Atrazine percolation coefficient P_UPDIS Phosphorus uptake distribution parameter PPERCO Phosphorus percolation coefficient PSP Phosphorus sorption coefficient PHOSKD Phosphorous soil partitioning coefficient ERORGP Phosphorus enrichment ratio BC4 Rate constant for mineralization of organic P to dissolved P in stream reach

6 S4. Simulated effects of operation scheduling The following table presents annual values of herbicide and sediment transport out of GCEW from 1993 to The coefficients of determination and slope of the regression between measured and simulated values are also presented. Supplemental Table S4. Effect of using planting progress reports on simulated annual atrazine and sediment export from GCEW. Annual Atrazine Loss, g ha -1 Sediment transport, kg ha -1 Year Measured With planting progress reports Without planting progress reports Measured With planting progress reports Without planting progress reports Mean r 2, Regression slope : The coefficient of determination and the regression slopes are between the measured and simulated values.

7 S5. Simulated effectiveness of herbicide incorporation Incorporating herbicide was simulated by adding a tillage operation after the application. Three tillage implements were considered: a no-till incorporation, a field cultivation, and a deeper disk cultivation. The following table shows the annual unit area loss for the watershed from the 18- year, 1993 to 2010 period. Supplemental Table S5. Effect of incorporation after application on simulated annual atrazine export from GCEW. Annual Atrazine Loss, g/ha Year Measured Simulated No Conservation Field Disk incorporation tillage implement Cultivation Average Reduction 2% 17% 36%

8 S6. Simulated effectiveness of reducing atrazine application rate The following table shows the simulated annual unit area loss for the watershed during the 18- year, 1993 to 2010 period. Supplemental Table S6. Effect of atrazine application rates on simulated atrazine export from GCEW. Annual Atrazine Loss, g/ha Simulated Year Measured Simulated percent reduction in 2.25 kg/ha 1.46 kg/ha atrazine loss % % % % % % % % % % % % % % % % % % Average % S7. References Alberts, E. E., R. C. Wendt, and R. E. Burwell Corn and soybean cropping effects on soil losses and C factors. Soil Sci. Soc. Am. J. 49: