The field used to represent corn production in Mississippi is located in the Southern Mississippi Valley Uplands. According to the 1997 Census of Agriculture, Mississippi is not a major corn producing state in the U.S. (not among the top 20 states) with approximately 600,000 acres in production. The crop is generally planted in the early Spring (April) and harvested beginning in August. Continuous corn is practice is much of the region, however, rotation with other crops such as soybean is the practiced as well. Most of the corn is planted for feed grain. Planting depth and row spacing (generally 30 inches) follows general practices for the U.S. Conventional tillage dominates with more than 50 percent of the practice, followed by conservation tillage, no-tillage, and ridge tillage. The crop is rarely grown under irrigation. The soil selected to simulate the field is a benchmark soil, Grenada silt loam. Grenada silt loam is a fine-silty, mixed, active, thermic Oxyaquic Fraglossudalfs. Most of the soil is used for the production of row crops such as corn, cotton, and soybeans, the principal crops. Grenada silt loam is a very deep, moderately well drained, medium to slow runoff, moderately permeable above a fragipan and slow in the fragipan soil. The fragipan is at a depth of about two feet. The soils formed in loess. They are located on uplands and stream terraces of low relief in the Southern Mississippi Valley Silty Uplands. Slopes are generally between 0 to 8 percent, but may range to 12 percent. The soils are extensive throughout the region. Grenada 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)||25.0 cm||PRZM Manual Figure 5.2 (EPA, 1998)|
|Method to Calculate Erosion (ERFLAG)||4 (MUSS)||PRZM Manual (EPA, 1998)|
|USLE K Factor (USLEK)||0.43 tons EI-1*||GLEAMS Table of Representative Soils (USDA, 1990)|
|USLE LS Factor (USLELS)||0.221||GLEAMS Table of Representative Soils (USDA, 1990)|
|USLE P Factor (USLEP)||1.00||PRZM Manual (EPA, 1998)|
|Field Area (AFIELD)||172 ha||Area of Shipman Reservoir watershed (EPA, 1999)|
|NRCS Hyetograph (IREG)||4||PRZM Manual Figure 5.12 (EPA, 1998)|
|Slope (SLP)||6%||Mid-point of series range. Selected according to QA/QC Guidance (EPA, 2001)|
|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)||0.25||PRZM Table 5.4 (EPA, 1998)|
|Maximum Active Root Depth (AMXDR)||90 cm||PRZM Input Collator; (Burns, 1992); PRZM Table 5.9 (EPA, 1998)|
|Maximum Canopy Coverage (COVMAX)||100||PRZM Input Collator (Burns, 1992); Set to default for most row crops (EPA, 2001)|
|Soil Surface Condition After Harvest (ICNAH)||3||PRZM Input Collator, PIC (Burns, 1992)|
|Date of Crop Emergence
(EMD, EMM, IYREM)
|11/04||Usual Planting and Harvest Dates for US Field Crops (USDA, 1984)|
|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)||91, 87, 88||Gleams Manual Table A.3, Fallow = SR/poor, Cropping and Residue = Row Crop, SR/Poor condition (USDA, 1990)|
|Manning's N Value (MNGN)||0.014||RUSLE Project, OA6CGSBC; Corn, grain, conventional tillage, Natchez, MS (USDA, 2000)|
|USLE C Factor (USLEC)||0.024 - 0.848||RUSLE Project; OA6CGSBC; Corn, grain, conventional tillage, Natchez, MS (USDA, 2000)|
|Total Soil Depth (CORED)||100 cm||PIC (Burns, 1992) Confirmed with: NRCS, National Soils Characterization Database (NRCS, 2001)|
|Number of Horizons (NHORIZ)||4 (3 Base, Top horizon split in two)|
|First, Second, Third and Fourth Soil Horizons (HORIZN = 1,2,3,4)|
|Horizon Thickness (THKNS)||
||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. 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.
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. 1990. Davis, F.M., R.A. Leonard, W.G. Knisel. GLEAMS User Manual, Version 1.8.55. USDA-ARS Southeast Watershed Research Laboratory, Tifton GA. SEWRL-030190FMD.
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).