The field used to represent soybean production in Mississippi is located in Yazoo County. According to the 1997 Census of Agriculture, Mississippi harvested more than 2 million acres of soybeans and ranks 12th in production in the U.S. The crop is generally planted in Spring (late April) and harvested beginning in September. Row spacing is generally 30 to 38-inches, but spacing could be a little as 7 inches. Field canopies tend to be very close to 100 percent early in the season and less as harvest nears. The crop may be grown under irrigation by furrow or canal systems. Most crops are planted by conventional tillage, but, no-till, or conservation methods are employed as well. The soil selected to simulate the field is a Loring silt loam. Loring silt loam is a fine-silty, mixed, active, thermic, Qxyaquic Fragiudalfs. Nearly all soils are cleared and used to grow cotton, small grains, soybeans, hay and pasture. Loring silt loam is a moderately well drained with a fragipan, medium to rapid runoff, moderate permeability above the fragipan and moderately slowly permeable in the fragipan soils formed in loess. They are located on level to strongly sloping uplands and stream terraces. Slopes are generally between 0 to 20 percent. The soils are extensive in the lower Mississippi drainage basin. Loring silt loam is a Hydrologic Group C soil.
|Starting Date||January 1, 1948||Meteorological File - Little Rock, AR (W13963)|
|Ending Date||December 31, 1983||Meteorological File - Little Rock, AR (W13963)|
|Pan Evaporation Factor (PFAC)||0.75||PRZM Manual Figure 5.1 (EPA, 1998)|
|Snowmelt Factor (SFAC)||0.25 cm C- 1||PRZM Manual Table 5.1 (EPA, 1998)|
|Minimum Depth of Evaporation (ANETD)||17.0 cm||PRZM Manual Figure 5.2 (EPA, 1998)|
|Method to Calculate Erosion (ERFLAG)||4 (MUSS)||PRZM Manual (EPA, 1998)|
|USLE K Factor (USLEK)||0.42 tons EI-1*||FARM Manual, Table 3.1 (EPA, 1985)|
|USLE LS Factor (USLELS)||0.051||Haan and Barfield, 1978.|
Input data from: Tim Pepper, Yazoo Co. Ag Extension Agent (622-746-2453)
|USLE P Factor (USLEP)||0.75||Tim Pepper, Yazoo Co. Ag Extension Agent (622-746-2453)|
|Field Area (AFIELD)||172 ha||Area of Shipman Reservoir watershed (EPA, 1999)|
|NRCS Hyetograph (IREG)||3||PRZM Manual Figure 5.12 (EPA, 1998)|
|Slope (SLP)||2%||Tim Pepper, Yazoo Co. Ag Extension Agent (622-746-2453)|
|Hydraulic Length (HL)||600 m||Shipman Reservoir (EPA, 1999)|
* EI = 100 ft-tons * in/ acre*hr
|Initial Crop (INICRP)||1||Set to one for all crops (EPA, 2001)|
|Initial Surface Condition (ISCOND)||1||PRZM Input Collator (Burns, 1992)|
|Number of Different Crops (NDC)||1||Set to crops in simulation - generally one|
|Number of Cropping Periods (NCPDS)||36||Set to weather data. Meteorological File - Little Rock, AR (W13963)|
|Maximum rainfall interception storage of crop (CINTCP)||0.2||PRZM Manual, Table 5.4 (EPA, 1998)|
|Maximum Active Root Depth (AMXDR)||30 cm||PRZM Manual, Table 5.9 (EPA, 1998)|
|Maximum Canopy Coverage (COVMAX)||100||Default for row crops (EPA, 2001)|
|Soil Surface Condition After Harvest (ICNAH)||3||Tim Pepper, Yazoo Co. Ag Extension Agent (622-746-2453)|
|Date of Crop Emergence
(EMD, EMM, IYREM)
|15/04||Tim Pepper, Yazoo Co. Ag Extension Agent (622-746-2453)|
|Date of Crop Maturity
(MAD, MAM, IYRMAT)
|Date of Crop Harvest
(HAD, HAM, IYRHAR)
|Maximum Dry Weight (WFMAX)||0.0||Set to "0" Not used in simulation|
|SCS Curve Number (CN)||87, 84, 86||Gleams Manual Table A.3; Fallow = SR/poor, Cropping and Residue = Row Crop, SR/poor|
|Manning's N Value (MNGN)||0.014||RUSLE Project, OA6SBCGC; Soybean, conventional tillage, Natchez, MS. Using boarding LRR (O) (USDA, 2000)|
|USLE C Factor (USLEC)||0.040 - 0.654||RUSLE Project; OA6SBCGC; Soybean, conventional tillage, Natchez, MS. Using boarding LRR (O) (USDA, 2000)|
|Total Soil Depth (CORED)||155 cm||PIC (Burns, 1992) Confirmed with: NRCS, National Soils Characterization Database (NRCS, 2001)|
|Number of Horizons (NHORIZ)||6|
|First, Second, Third, Fourth, Fifth, and Sixth Soil Horizons (HORIZN = 1,2,3,4,5,6)|
||PIC (Burns, 1992) Confirmed with: NRCS, National Soils Characterization Database (NRCS, 2001) http://soils.usda.gov/survey/nscd/|
|Bulk Density (BD)||
|Initial Water Content (THETO)||
|Compartment Thickness (DPN)||
|Field Capacity (THEFC)||
|Wilting Point (THEWP)||
|Organic Carbon Content (OC)|
Burns. 1992. Burns, L.A., (Coordinator), B.W. Allen, Jr., M.C. Barber, S.L. Bird, J.M. Cheplick, M.J. Fendley, D.R. Hartel, C.A. Kittner, F.L. Mayer, Jr., L.A. Suarez, and S.E. Wooten. Pesticide and Industrial Chemical Risk Analysis and Hazard Assessment, Version 3.0. (PIRANHA) Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Athens, GA. 1992.
EPA. 1985. Field Agricultural Runoff Monitoring (FARM) Manual, (EPA/600/3-85/043) Environmental Research Laboratory, U.S. Environmental Protection Agency, Athens, GA.
EPA. 1998. Carsel, R.F., J.C. Imhoff, P.R. Hummel, J.M. Cheplick, and A.S. Donigian, Jr. PRZM-3, A Model for Predicting Pesticide and Nitrogen Fate in the Crop Root and Unsaturated Soil Zones: Users Manual for Release 3.0. National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Athens, GA.
EPA. 1999. Jones, R.D., J. Breithaupt, J. Carleton, L. Libelo, J. Lin, R. Matzner, and R. Parker. Guidance for Use of the Index Reservoir in Drinking Water Exposure Assessments. Environmental Fate and Effects Division, Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington. D.C.
EPA. 2001. Abel, S.A. Procedure for Conducting Quality Assurance and Quality Control of Existing and New PRZM Field and Orchard Crop Standard Scenarios. Environmental Fate and Effects Division, Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington, D.C.
Haan, C.T. and B.J. Barfield. 1978. Hydrology and Sedimentology of Surface Mined Lands. Office of Continuing Education and Extension, College of Engineering, University of Kentucky, Lexington, Kentucky 40506. pp. 286.
USDA. 1984. Usual Planting and Harvesting Dates for U.S. Field Crops, Statistical Reporting Service, U.S. Department of Agriculture, Agriculture Handbook #628, pp.78.
USDA. 2000. Revised Universal Soil Loss Equation (RUSLE) EPA Pesticide Project. U.S. Department of Agriculture, National Resources Conservation Service (NRCS) and Agricultural Research Service (ARS).