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CALIFORNIA CITRUS (Southern)
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The field used to represent citrus production in California is located in Fresno County in the Central Valley, although citrus production areas are quite extensive (San Joaquin, Coastal-Intermediate Region, Imperial Valley, Coachella Valley, and the Southern Interior Region). According to the 1997 Census of Agriculture, California is the major producer of citrus (lemons and oranges) for the fresh market, and among the highest producers in other citrus (grapefruit, tangerines, tangelos, and mandarins). Citrus is generally grown on the foothills to avoid frost damage. Areas under and between rows of trees are generally non-cultivated/non-maintained. Row spacing is approximately 22 feet and between tree spacing is approximately 18 feet. Row canopies tend to be 100 percent, while the canopy between rows is less to permit the operation of maintenance and harvest equipment. Irrigation is mostly by low-volume drip or micro-sprinkler systems, although furrow and overhead sprinklers are also used. The soil selected to simulate the field is a benchmark soil, Exeter loam. Exeter loam, is a fine-loamy, mixed, superactive, thermic Typic Durixeralfs. These soils are often used for citrus production under irrigation. Exeter loam is a moderately deep, moderately well drained, very slow to medium runoff soil that formed in alluvium mainly from granite sources. The soil also consists of a duripan. The Exeter loam has moderately slow permeability above the duripan and very slow permeability within the duripan. These soil are generally found on alluvial fans and stream terraces at elevations of up to 700 feet above mean sea level and have slopes of 0 to 9 percent. The soil is extensive in MLRA 17. Exeter loam is a Hydrologic Group C soil.
| Parameter | Value | Source |
|---|---|---|
| Starting Date | January 1, 1948 | Meteorological File - Southern: Bakersfield, CA (W23155) |
| Ending Date | December 31, 1983 | Meteorological File - Southern: Bakersfield, CA (W23155) |
| Pan Evaporation Factor (PFAC) | 0.7 | PRZM Manual Figure 5.1 (EPA, 1998) |
| Snowmelt Factor (SFAC) | 0.55 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) |
| Parameter | Value | Source |
|---|---|---|
| Method to Calculate Erosion (ERFLAG) | 4 (MUSS) | PRZM Manual (EPA, 1998) |
| USLE K Factor (USLEK) | 0.28 tons EI-1* | NRI - Average value listed for the soil series Exeter |
| USLE LS Factor (USLELS) | 0.21 | NRI - Average value listed for the soil series Exeter |
| USLE P Factor (USLEP) | 1.0 | NRI - Average value listed for the soil series Exeter |
| 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) | 5% | Mark Freeman Fresno County Cooperative Extension Agent. |
| Hydraulic Length (HL) | 600 m | Shipman Reservoir (EPA, 1999) |
| Irrigation Flag (IRFLAG) | 2 (cropping period only) | Mark Freeman Fresno County Cooperative Extension Agent. |
| Irrigation Type (IRTYP) | 1 (Flood) | Mark Freeman Fresno County Cooperative Extension Agent. |
| Leaching Factor (FLEACH) | 0.1 | Estimated |
| Fraction of Water Capacity when Irrigation is Applied (PCDEPL) | 0.55 | Mark Freeman Fresno County Cooperative Extension Agent. |
| Maximum Rate at which Irrigation is Applied (RATEAP) | 0.4 cm hr-1 | PRZM Manual, Table 5.33 (EPA, 1998) |
* EI = 100 ft-tons * in/ acre*hr
| Parameter | Value | Source |
|---|---|---|
| Initial Crop (INICRP) | 1 | Set to one for all crops (EPA, 2001) |
| Initial Surface Condition (ISCOND) | 3 | Mark Freeman Fresno County Cooperative Extension Agent. |
| 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 - Bakersfield, CA (W23155) |
| Maximum rainfall interception storage of crop (CINTCP) | 0.25 | Maximum recommended value for grass (EPA, 2001) |
| Maximum Active Root Depth (AMXDR) | 60 cm | Mark Freeman Fresno County Cooperative Extension Agent. |
| Maximum Canopy Coverage (COVMAX) | 80 | Mark Freeman Fresno County Cooperative Extension Agent. |
| Soil Surface Condition After Harvest (ICNAH) | 3 | Mark Freeman Fresno County Cooperative Extension Agent. |
| Date of Crop Emergence (EMD, EMM, IYREM) |
02/01 | Value set to a default evergreen cycle with no specific crop growth milestone such as flowering of fruit set. |
| Date of Crop Maturity (MAD, MAM, IYRMAT) |
03/01 | Value set to a default evergreen cycle with no specific crop growth milestone such as flowering of fruit set. |
| Date of Crop Harvest (HAD, HAM, IYRHAR) |
31/12 | Value set to a default evergreen cycle with no specific crop growth milestone such as flowering of fruit set. |
| Maximum Dry Weight (WFMAX) | 0.0 | Set to "0" Not used in simulation |
| SCS Curve Number (CN) | 84, 79, 82 | Gleams Manual Table A.3, Meadows, no fallow conditions (USDA, 1990) |
| Manning's N Value (MNGN) | 0.023 | RUSLE Project; D26CCCCM for cover alley citrus (USDA, 2000) |
| USLE C Factor (USLEC) | 0.096 - 0.150 | RUSLE Project; Variable with date, D26CCCCM for cover alley citrus (USDA, 2000) |
| Parameter | Value | Verification Source |
|---|---|---|
| Total Soil Depth (CORED) | 183 cm | NRCS, National Soils Characterization Database (NRCS, 2001) |
| Number of Horizons (NHORIZ) | 2 (Base horizons) | |
| First and Second Soil Horizons (HORIZN = 1,2) | ||
| Horizon Thickness (THKNS) |
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NRCS, National Soils Characterization Database (NRCS, 2001)
http://soils.usda.gov/survey/nscd/
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| Bulk Density (BD) |
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| Initial Water Content (THETO) |
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| Compartment Thickness (DPN) |
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| Field Capacity (THEFC) |
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| Wilting Point (THEWP) |
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| Organic Carbon Content (OC) |
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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. 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).