TEXAS WHEAT (Winter)
The field used to represent wheat production in Texas is located in the Blacklands region, however, wheat is grown throughout Texas. According to the 1997 Census of Agriculture, Texas ranked 7th among the major wheat producing states in the U.S. with more than 2.5 million acres in production. Most wheat is grown in the High Plains region of the state. Wheat is planted in the early fall (mid-September through October) and harvested in the summer. Row spacing ranges from 6 to 9 inches with seeds planted at a depth of 2 inches or less. The soil selected to simulate the field is a Crockett fine sandy loam. Crockett fine sandy loam is a fine, smectitic, thermic Udertic Paleustalfs. The series is mainly used to grow cotton, grain sorghum, and small grains, but more than half the acreage is now in pasture. Crocket fine sandy loam is a deep. Moderately well drained, very slowly permeable soil with low to very high runoff depending on slope. These soils formed in residuum derived from weathered alkaline marine clays, sandy clays, or shale, interbedded with sandier materials mainly of Cretaceous age. They are located on broad nearly level to moderately sloping uplands. Slopes are generally between 1 to 5 percent, but may range from 0 to 10 percent. The series is extensive in MLRA 86, 87A, and 87B. Crockett fine sandy loam is a Hydrologic Group C soil.
|Starting Date||January 1, 1950||Meteorological File - Austin, TX (W13958)|
|Ending Date||December 31, 1983||Meteorological File - Austin, TX (W13958)|
|Pan Evaporation Factor (PFAC)||0.71||PRZM Manual Figure 5.1 (EPA, 1998.)|
|Snowmelt Factor (SFAC)||0.5 cm C- 1||PRZM Manual Table 5.1 (EPA, 1998)|
|Minimum Depth of Evaporation (ANETD)||10.0 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*||FARM Manual, Table 3.1 (EPA, 1985)|
|USLE LS Factor (USLELS)||0.103365||Haan and Barfield, 1978|
|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)||1||PRZM Manual Figure 5.12 (EPA, 1998)|
|Slope (SLP)||3%||consultation with Tom Gerik (254.774.6128)|
most highly erodible soils with slopes >5% in Blacklands area have been put into CRP or pasture. Wheat is mostly grown on soils with slopes 1-3%; the best wheat soils are Houston clay or Austin.
|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||Set to default for fallow surface prior to planting|
|Number of Different Crops (NDC)||1||Set to crops in simulation - generally one|
|Number of Cropping Periods (NCPDS)||36||Set to weather data. Austin, TX (W13958)|
|Maximum rainfall interception storage of crop (CINTCP)||0.2||PRZM Table 5.4 (EPA, 1998)|
|Maximum Active Root Depth (AMXDR)||110 cm||Consultation with Tom Gerik (254-774-6128)|
|Maximum Canopy Coverage (COVMAX)||99||Tom Gerik (254-774-6128)|
|Soil Surface Condition After Harvest (ICNAH)||3||Tom Gerik (254-774-6128), winter wheat in Blacklands area is harvested from mid-May to early June. The earliest repeat crop is the following spring. The stubble is left alone until mid to late summer, when it is disked once in August/September.|
|Date of Crop Emergence
(EMD, EMM, IYREM)
|10/10||Usual Planting and Harvesting Dates for U.S. 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)||94, 87, 88||Gleams Manual Table; Fallow = Fallow SR/poor; Cropping and Residue = Small grain SR/good (USDA, 1990)|
|Manning's N Value (MNGN)||0.014||RUSLE Project, J94CTCTN; Cotton, no-tillage, Waco TX (USDA, 2000)|
|USLE C Factor (USLEC)||0.026 - 0.318||RUSLE Project; J94CTCTN; Cotton, no-tillage, Waco TX (USDA, 2000)|
|Total Soil Depth (CORED)||100 cm||PIC (Burns, 1992) Confirmed with: NRCS, National Soils Characterization Database (NRCS, 2001)|
|Number of Horizons (NHORIZ)||3 (Top horizon split in two)|
|First, Second, and Third Soil Horizons (HORIZN = 1,2,3)|
|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. 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. 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).