The field used to represent cotton production in Texas is located in Milam County, although cotton is grown throughout Texas. According to the 1997 Census of Agriculture, Texas ranked 1st among the major cotton producing states in the U.S. with more than 5 million acres in production. Most cotton is grown in the High Plains (67%) and Rolling Plains (20%) regions of the state. Cotton is planted in the late winter/early Spring (February and March) in the Lower Rio Grande region and progresses into June in the southern High Plains. Cotton is planted by the "skip-row" or "ultra-narrow row" method. Skip row refers to the technique where every third row is "skipped" to permit the crop to take advantage of soil moisture in semi-arid regions. Ultra-narrow row (UNR) cotton is spaced at 20 inches apart which tends to increase yields and efficiency of productions systems. Both systems require the use of irrigation. Fifty percent of cotton production in the High Plains is irrigated and less than ten percent in the Rolling Plains is irrigated. Furrow irrigation is the most common in the Lower Rio Grande and sprinkler systems are most common in the High Plains. Low Energy Precision Application center pivot irrigation is beginning to make inroad in the area because of its lower pressure requirements, lower evaporation losses and water savings. Row spacing is generally 38-inches with 3-4 plants per foot row in all but UNR cotton. Row canopies tend to be very close to 100 percent, while the canopy between rows is much less. All cotton is defoliated prior to harvesting. Conventional tillage is the dominant practice. 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. Crockett 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)||0.7||PRZM Manual Figure 5.1 (EPA, 1998)|
|Snowmelt Factor (SFAC)||0.3 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)||0.3 tons EI-1*||FARM Manual, Table 3.1 (EPA, 1985)|
|USLE LS Factor (USLELS)||0.365||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)||4||PRZM Manual Figure 5.12 (EPA, 1998)|
|Slope (SLP)||2.5%||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||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)||60 cm||PRZM Input Collator, PIC (Burns, 1992); PRZM Table 5.9 (EPA, 1998)|
|Maximum Canopy Coverage (COVMAX)||100||PRZM Input Collator, PIC (Burns, 1992) Per QA/QC Guidance (EPA, 2001)|
|Soil Surface Condition After Harvest (ICNAH)||3||Residues left on field until following year or cover crop is planted.|
|Date of Crop Emergence
(EMD, EMM, IYREM)
|25/04||Personal communication with Cullen "Dusty" Tittle, Milam Co. Extension Agent. Maturation and harvest close together because the plants are desiccated anywhere from late Aug through Sept.|
|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)||89, 86, 87||Gleams Manual Table; Fallow = Fallow SR/CT/poor; Cropping and Residue = Row Crop SR/CT/poor (USDA, 1990)|
|Manning's N Value (MNGN)||0.023||RUSLE Project, J94CTCTN; Cotton, no-tillage, Waco TX (USDA, 2000)|
|USLE C Factor (USLEC)||0.111 - 0.365||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. 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).