**Barton Springs Orchard**

This scenario is intended to represent an orchard that may include
cultivation of peaches, nectarines or pecans. USDA data for Hays and
Travis counties do not include harvest data for these crops from
1990-2007 (USDA 2007); however, the 2002 agricultural census for the two
counties includes over 2000 acres of land in orchards (USDA 2002).
Discussions with extension agents in Hays and Travis counties indicated
that some cultivation of peaches and nectarines occurs in the Barton
Springs Segment (BSS) of the Edward Aquifer, specifically in Hays County
(Bryan Davis, personal communication). Crop parameters for this scenario
were chosen to be reflective of a peach orchard in the BSS.

For soil parameters, the Brackett soil series was selected because it is
a benchmark soil, is highly representative of areas in the BSS, and
represents a soil with high-end values for vulnerability, drainage,
erodibility, and slope. Brackett is a Hydrologic Group C soil with a
USLE K factor of 0.37. Soil parameters for the "Brackett-Rock
outcrop-Comfort complex, 1 to 8 percent slopes" were selected from Soil
Data Mart to parameterize this scenario (USDA 2001; USDA 2006).

The meteorological station selected for this scenario is located in
Austin, Texas. This station is the closest available weather station
that includes data required for PRZM.

Number range CHAPTER

+-----------------+----------+-----------------------------------------+
| **Table 1. PRZM |          |                                         |
| 3.12 Climate    |          |                                         |
| and Time        |          |                                         |
| Parameters for  |          |                                         |
| Barton Springs, |          |                                         |
| TX.**           |          |                                         |
+-----------------+----------+-----------------------------------------+
| **Parameter**   | *        | **Source/Comments**                     |
|                 | *Value** |                                         |
+-----------------+----------+-----------------------------------------+
| Starting Date   | Jan. 1,  | Meteorological File from Austin, TX     |
|                 | 1961     | (W13958)                                |
+-----------------+----------+-----------------------------------------+
| Ending Date     | Dec. 31, | Meteorological File from Austin, TX     |
|                 | 1990     | (W13958)                                |
+-----------------+----------+-----------------------------------------+
| Pan Evaporation | 0.69     | PRZM Manual Figure 5.1 (EPA 1998).      |
| Factor (PFAC)   |          |                                         |
+-----------------+----------+-----------------------------------------+
| Snowmelt Factor | 0.36     | PRZM Manual, Table 5.1 (EPA 1998).      |
| (SFAC)          |          |                                         |
+-----------------+----------+-----------------------------------------+
| Minimum Depth   | 25       | Mid point of range (20-30), PRZM        |
| of              |          | Manual, Figure 5.2 (EPA 1998).          |
|                 |          |                                         |
| Evaporation     |          |                                         |
| (ANETD)         |          |                                         |
+-----------------+----------+-----------------------------------------+

  ----------------- ----------- ------------------------------------------
  **Table 2. PRZM               
  3.12 Erosion and              
  Landscape                     
  Parameters for                
  Barton Springs -              
  orchard.**                    

  **Parameter**     **Value**   **Source/Comments**

  Method to         4 (MUSS)    Default value.
  Calculate Erosion             
  (ERFLAG)                      

  USLE K Factor     0.37 tons   Brackett-Rock Outcrop-Comfort Complex Soil
  (USLEK)           EI^-1^ ◊    (USDA 2006).

  USLE LS Factor    0.69        Calculated according to Haan and Barfield
  (USLELS)                      (1978) equation: LS =
                                ((λ/72.6)^m^)((430x^2^ + 30x +
                                0.43)/6.613), where λ = slope length, x =
                                SLP/100 and m = constant. In this case, λ
                                = 400 m (default value) and m = 0.4 (EPA
                                2004).

  USLE P Factor     1           Default for orchards.
  (USLEP)                       

  Field Area        10 ha       Default value for area of standard farm
  (AFIELD)                      pond.

  NRCS Hyetograph   4           PRZM Manual, Figure 5.12 (EPA, 1998).
  (IREG)                        

  Slope (SLP)       4 %         Brackett-Rock Outcrop-Comfort Complex Soil
                                Slope range 1-8% (USDA 2006).

  Hydraulic Length  356 m       Default value for Pond (EPA, 2004)
  (HL)                          

  Irrigation Flag   2           Irrigation during cropping period (Kamas
  (IRFLAG)                      et al. 1998).

  Irrigation Type   4           Drip irrigation (Kamas et al. 1998).
  (IRTYP)                       

  Leaching Factor   0           Default value (EPA 2005).
  (FLEACH)                      

  Fraction of Water 0.5         Default value (EPA 2005).
  Capacity when                 
  Irrigation is                 
  Applied (PCDEPL)              

  Maximum Rate at   0.056       Default value (for cropping period CN
  which Irrigation              (79)) (EPA 2005).
  is Applied                    
  (RATEAP)                      

  ◊ EI = 100                    
  ft-tons \* in/                
  acre\*hr                      
  ----------------- ----------- ------------------------------------------

+-----------------------+-----------+---------------------------------+
| **Table 3. PRZM 3.12  |           |                                 |
| Crop Parameters for   |           |                                 |
| Barton Springs -      |           |                                 |
| orchard.**            |           |                                 |
+-----------------------+-----------+---------------------------------+
| **Parameter**         | **Value** | **Source/Comments**             |
+-----------------------+-----------+---------------------------------+
| Initial Crop (INICRP) | 1         | Default value                   |
+-----------------------+-----------+---------------------------------+
| Initial Surface       | 3         | Consistent with GA peach        |
| Condition             |           | scenario.                       |
|                       |           |                                 |
| (ISCOND)              |           |                                 |
+-----------------------+-----------+---------------------------------+
| Number of Different   | 1         | Set to number of crops in       |
| Crops (NDC)           |           | simulation. Default value.      |
+-----------------------+-----------+---------------------------------+
| Number of Cropping    | 30        | Set to weather data in          |
| Periods (NCPDS)       |           | meteorological file: Austin, TX |
|                       |           | (W13958).                       |
+-----------------------+-----------+---------------------------------+
| Maximum rainfall      | Number    | Consistent with GA peach        |
| interception storage  | range     | scenario.                       |
| of crop (CINTCP)      | CH        |                                 |
|                       | APTER0.25 |                                 |
+-----------------------+-----------+---------------------------------+
| Maximum Active Root   | 43        | Set to CORED. According to GA   |
| Depth (AMXDR)         |           | peach scenario, roots may grow  |
|                       |           | in excess of 5 feet (152 cm).   |
+-----------------------+-----------+---------------------------------+
| Maximum Canopy        | 60        | Consistent with GA peach        |
| Coverage (COVMAX)     |           | scenario.                       |
+-----------------------+-----------+---------------------------------+
| Soil Surface          | 3         | Consistent with GA peach        |
| Condition After       |           | scenario.                       |
| Harvest (ICNAH)       |           |                                 |
|                       |           | Residue is left on a field      |
|                       |           | after harvest.                  |
+-----------------------+-----------+---------------------------------+
| Maximum Canopy Height | 300 cm    | Consistent with GA peach        |
| (HTMAX)               |           | scenario.                       |
+-----------------------+-----------+---------------------------------+
| Date of Crop          | 1/4/61    | Peach trees require chilling    |
| Emergence             |           | temperatures (32-45^o^F) to     |
|                       |           | break dormancy, which begins    |
| (EMD, EMM, IYREM)     |           | vegetative growth and flower    |
|                       |           | production (Kamas et al. 1998). |
|                       |           | Austin mean temperatures for    |
|                       |           | 1971-2000 indicate chilling     |
|                       |           | temperatures are reasonable to  |
|                       |           | occur November- March (NOAA     |
|                       |           | 2005). Emergence and harvest    |
|                       |           | dates are set according to this |
|                       |           | information. Harvest is assumed |
|                       |           | to be when peach trees are      |
|                       |           | defoliated. Maturity            |
|                       |           | corresponds to the time when    |
|                       |           | the trees are fully leafed out. |
|                       |           | This time is estimated to take  |
|                       |           | 1 month.                        |
+-----------------------+-----------+---------------------------------+
| Date of Crop Maturity | 1/5/61    |                                 |
|                       |           |                                 |
| (MAD, MAM, IYRMAT)    |           |                                 |
+-----------------------+-----------+---------------------------------+
| Date of Crop Harvest  | 16/11/61  |                                 |
|                       |           |                                 |
| (HAD, HAM, IYRHAR)    |           |                                 |
+-----------------------+-----------+---------------------------------+
| Maximum Dry Weight    | 0.0       | Not used in scenario.           |
| (WFMAX)               |           |                                 |
+-----------------------+-----------+---------------------------------+
| SCS Curve Number (CN) | 84, 79,   | Gleams Manual Table H-4,        |
|                       | 82        | meadow, hydrologic group C,     |
|                       |           | good condition (USDA, 2000)     |
+-----------------------+-----------+---------------------------------+
| Manning\'s N Value    | 0.023     | San Antonio winter wheat sgp 30 |
| (MNGN)                |           | (I93WWWWM). Mulch tillage (MT), |
|                       |           | which includes a few tillage    |
|                       |           | operations that are less in     |
|                       |           | number and less aggressive than |
|                       |           | conventional tillage. This is   |
|                       |           | inconsistent with the GA peach  |
|                       |           | scenario, which incorporates    |
|                       |           | conventional tillage. The cover |
|                       |           | code includes light cover (5)   |
|                       |           | which is commonly used with     |
|                       |           | mulch till (7-35% residue cover |
|                       |           | on soil surface).               |
+-----------------------+-----------+---------------------------------+
| USLE C Factor (USLEC) | 0.028 --  | San Antonio winter wheat sgp 30 |
|                       | 0.162     | (I93WWWWM).                     |
+-----------------------+-----------+---------------------------------+

+---------+-------------------+---------------------------------------+
| **Table |                   |                                       |
| 4. PRZM |                   |                                       |
| 3.12    |                   |                                       |
| Bracke  |                   |                                       |
| tt-Rock |                   |                                       |
| O       |                   |                                       |
| utcrop- |                   |                                       |
| Comfort |                   |                                       |
| Complex |                   |                                       |
| Soil    |                   |                                       |
| Par     |                   |                                       |
| ameters |                   |                                       |
| for     |                   |                                       |
| Barton  |                   |                                       |
| Sp      |                   |                                       |
| rings - |                   |                                       |
| orc     |                   |                                       |
| hard.** |                   |                                       |
+---------+-------------------+---------------------------------------+
| **Para  | **Value**         | **Source/Comments**                   |
| meter** |                   |                                       |
+---------+-------------------+---------------------------------------+
| Total   | 43 cm             | NRCS Soil Data Mart Database, Hays    |
| Soil    |                   | County, for Brackett-Rock             |
| Depth   |                   | outcrop-Comfort complex, 1 to 8       |
| (CORED) |                   | percent slopes.                       |
|         |                   | (<                                    |
|         |                   | http://soildatamart.nrcs.usda.gov/>). |
|         |                   |                                       |
|         |                   | Additional data were listed for a     |
|         |                   | 4^th^ HORIZN. However, these were not |
|         |                   | included in this soil profile since   |
|         |                   | the 4^th^ HORIZN is composed of       |
|         |                   | bedrock.                              |
|         |                   |                                       |
|         |                   | Number range CHAPTERPRZM Scenario     |
|         |                   | Guidance (2004).                      |
|         |                   |                                       |
|         |                   | Adjusted using the relationship % OC  |
|         |                   | = % Organic Matter/1.724 (Doucette    |
|         |                   | 2000).                                |
+---------+-------------------+---------------------------------------+
| Number  | 3                 |                                       |
| of      |                   |                                       |
| H       |                   |                                       |
| orizons |                   |                                       |
| (       |                   |                                       |
| NHORIZ) |                   |                                       |
+---------+-------------------+---------------------------------------+
| Horizon | 10 cm (HORIZN =1) |                                       |
| Th      |                   |                                       |
| ickness | 5 cm (HORIZN =2)  |                                       |
| (THKNS) |                   |                                       |
|         | 28 cm (HORIZN =3) |                                       |
+---------+-------------------+---------------------------------------+
| Bulk    | 1.4 g/cm3 (HORIZN |                                       |
| Density | =1)               |                                       |
| (BD)    |                   |                                       |
|         | 1.4 g/cm3 (HORIZN |                                       |
|         | =2)               |                                       |
|         |                   |                                       |
|         | 1.4 g/cm3 (HORIZN |                                       |
|         | =3)               |                                       |
+---------+-------------------+---------------------------------------+
| Initial | 0.28 cm3/cm3      |                                       |
| Water   | (HORIZN =1)       |                                       |
| Content |                   |                                       |
| (THETO) | 0.28 cm3/cm3      |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.251 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Comp    | 0.1 cm (HORIZN    |                                       |
| artment | =1)               |                                       |
| Th      |                   |                                       |
| ickness | 5 cm (HORIZN =2)  |                                       |
| (DPN)   |                   |                                       |
|         | 4 cm (HORIZN =3)  |                                       |
+---------+-------------------+---------------------------------------+
| Field   | 0.28 cm3/cm3      |                                       |
| C       | (HORIZN =1)       |                                       |
| apacity |                   |                                       |
| (THEFC) | 0.28 cm3/cm3      |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.251 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Wilting | 0.164 cm3/cm3     |                                       |
| Point   | (HORIZN =1)       |                                       |
| (THEWP) |                   |                                       |
|         | 0.164 cm3/cm3     |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.142 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Organic | 1.16 % (HORIZN    |                                       |
| Carbon  | =1)               |                                       |
| Content |                   |                                       |
| (OC)    | 1.16 % (HORIZN    |                                       |
|         | =2)               |                                       |
|         |                   |                                       |
|         | 0.73 % (HORIZN    |                                       |
|         | =3)               |                                       |
+---------+-------------------+---------------------------------------+

**References**

Davis, B. 2006. Texas Cooperative Extension. Hays County Extension
Agent. Agriculture and Natural Resources. Personal communication. 12
December 2006.

Number range CHAPTEREPA. 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.

Number range CHAPTEREPA. 2004. Pesticide Root Zone Model (PRZM) Field
and Orchard Crop Scenarios: Guidance for Selecting Field Crop and
Orchard Scenario Input Parameters. November 15, 2001; Revisions July
2004.

EPA. 2005. Irrigation Guidance for developing PRZM Scenario. June 15,
2005.

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.

Kamas, J., McEachern, G.R., Stein, L., and N. Roe. 1998. Peach
production in Texas. Texas A&M University, Extension. Available URL:
http://aggie-horticulture.tamu.edu/extension/peach/peach.html.
\[Accessed 16 January 2007\].

NOAA. 2005. Austin climate summary: average montyly temperatures, rain,
and freeze data. National Oceanic & Atmospheric Administration. National
Weather Service Forecast Office. Last modified 26 October 2005.
Available URL: http://www.srh.noaa.gov/ewx/html/cli/ausnorm.htm
\[Accessed 16 January 2007\].

USDA 2000. Knisel, W.G., and Davis, F.M., 2000, GLEAMS: Groundwater
Loading Effects of Agricultural Management Systems, Version 3.0:
Agricultural Research Service, U.S. Department of Agriculture,
Publication No. SEWRL-WGK/FMD-050199, 191 p.

USDA. 2002. 2002 Census of Agriculture. U.S. Department of Agriculture,
National Agricultural Statistics Service. Accessed March 2006. Online
at: http://www.nass.usda.gov/index.asp.

Number range CHAPTERUSDA. 2001. Official Series Description. Brackett
Series. Information from the website:
http://ortho.ftw.nrcs.usda.gov/osd/dat/B/BRACKETT.html.

USDA. 2006. Soil Survey Areas of Hays Counties, Texas. U.S. Department
of Agriculture, Natural Resources Conservation Service (NRCS), Soil Data
Mart. March 1, 2006. Online at: http://soildatamart.nrcs.usda.gov.

USDA. 2007. U.S. Department of Agriculture, National Agricultural
Statistics Service, Agricultural Statistics Data Base. January 17, 2007.
Online at: http://www.nass.usda.gov/.