**Southern California**

**Outdoor Ornamental Nursery Scenario**

This scenario is one of a suite of scenarios intended to represent
outdoor ornamental nursery scenarios in the United States. It should be
noted that nurseries are diverse and represent a range of topographic,
cultivation, and plant types. Scenarios, when possible have been
developed to represent conservative nursery practices that will yield
"high-end" runoff, but not unrealistic of actual nurseries in the area.
Similarly, selection of curve numbers are based on best available data
from TR-55 until further calibration can be performed using regional
runoff data, which at the time of scenario development is generally
unavailable for nurseries. Figure 1 provides an overview of available
curve numbers from TR-55 in order to provide context to the relative
magnitude of the curve number used in this scenario. The closest curve
number that could be associated with outdoor nurseries is for
"farmsteads", due to similar cover conditions. Curve numbers are
generally among the highest available, exceeded primarily by soils in
poor condition.

This scenario is parameterized to generally represent outdoor ornamental
nursery production in southern California. The scenario nominally
represents outdoor ornamental nurseries in San Diego County, CA since it
is the county with the most number of acres in production in the region.
In 2002, the state of California ranked number 1 in the U.S. for total
number of ornamental nursery acres in the outdoors (i.e., not under
glass), with nearly 52,000 acres in the open (USDA 2002a). San Diego
County ranks number 1 in the state with approximately 10,139 acres of
outdoor nurseries in the county according to the 2002 USDA census of
agriculture (USDA 2002a). The total value of agricultural products sold
in San Diego County in 2002 was approximately 950 million dollars, of
which approximately 65% of the revenue was generated from the sale of
nursery and greenhouse crops (and sod) (USDA 2002b). San Diego County is
primarily within MLRA's 19 and 20.

Plants cultivated by outdoor nurseries are diverse. For this scenario,
crop parameters have been selected when possible to be representative of
typical outdoor nursery practices in southern California. Based on local
expert information as well as nursery production and pesticide
application data, this scenario has been parameterized to represent
outdoor container nurseries producing fruit and nut trees. Nurseries in
southern California are primarily wholesale (J. Bethke, personal
communication) and are typically container operations (C. Wilen,
personal communication). According to the USDA 2003 nursery crops
summary (USDA, 2004a), the most commonly produced nursery plants in
California are fruit and nut trees (33 million plants) and deciduous
shrubs (27 million plants). In addition, fruit and nut trees receive
approximately 66 thousand pounds of pesticide active ingredient per year
(USDA, 2004b). In 2003, the majority (52%) of fruit and nut trees in
California were sold in containers. Lesser amounts were sold as
bare-root and balled-&-burlapped. Irrigation is often used. Methods are
primarily drip irrigation and most nurseries have on site irrigation
specialists (J. Bethke, personal communication).

Metfile W23188 is located in San Diego, CA and is the closest
meteorological station to San Diego County, CA. It is within
approximately 28 miles of the county centroid. Its data were collected
in San Diego, CA located in the south-western part of the state. The
station is located approximately 4 meters above mean sea level (AMSL).
Although San Diego County is mountainous with elevations ranging from
near sea level to over 3,000 feet AMSL, the San Diego station is
expected to be the most representative climate station in the area. The
next closest station is Long Beach located approximately 100 miles from
the scenario and is also approximately 4 meters AMSL. San Diego receives
an average rainfall of 10.8 inches (NOAA, 2006). San Diego County's
climate is arid and irrigation is required year-round (Jim Bethke,
personal communication)

Nursery soils in southern California are commonly sandy loams (Jim
Bethke, personal communication). Exact locations and geographic extent
of nurseries in the region are not available; therefore soils were
selected based on soil recommendations of local experts, the geographic
extent of nursery supporting soils in the area, the drainage group,
slope, and erodibility. The Cieneba series was selected for this
scenario since it is a sandy loam, is of large extent in the region
(USDA, 1999; 2006), and is a hydrologic group C soil (Table 5).

The Cieneba series consists of very shallow and shallow, somewhat
excessively drained soils that formed in material weathered from
granitic rock (USDA, 1999). Cieneba is a Hydrologic Group C soil, which
represents approximately 17% of the soils in San Diego County (Table 5).
Cieneba soils have a USLE K factor ranging from 0.24 to 0.32, which is
common among soils in San Diego County. Six soils have a USLE K greater
than 0.32, however these soils are significantly less extensive than
Cieneba and are not sandy loams which are typical of nurseries in the
area (Jim Bethke, personal communication). Approximately 9% of San Diego
County soils have a pH range lower than Cieneba soils. Based on the
official soil series description, Ceineba soils have an A horizon from 0
to 10 inches (0-25 cm) deep and a C horizon from 10 to over 30 inches
(25-76 cm) deep (USDA, 2006). Soil parameters are based on "Cieneba
coarse sandy loam, 15 to 30 percent slopes" soils based on typical
nursery soils and slope range up to 35 degrees (Jim Bethke, personal
communication).

+-----------------+----------+-----------------------------------------+
| **Table 1. PRZM |          |                                         |
| 3.12 Climate    |          |                                         |
| and Time        |          |                                         |
| Parameters for  |          |                                         |
| Southern        |          |                                         |
| California --   |          |                                         |
| Ornamental      |          |                                         |
| Nurseries.**    |          |                                         |
+-----------------+----------+-----------------------------------------+
| **Parameter**   | *        | **Source/Comments**                     |
|                 | *Value** |                                         |
+-----------------+----------+-----------------------------------------+
| Starting Date   | Jan. 1,  | Meteorological File San Diego, CA       |
|                 | 1961     | (W23188)                                |
+-----------------+----------+-----------------------------------------+
| Ending Date     | Dec. 31, | Meteorological File San Diego, CA       |
|                 | 1990     | (W23188)                                |
+-----------------+----------+-----------------------------------------+
| Pan Evaporation | 0.7      | PRZM Manual Figure 5.1. Value           |
| Factor (PFAC)   |          | represents the center of San Diego      |
|                 |          | county.                                 |
+-----------------+----------+-----------------------------------------+
| Snowmelt Factor | 0        | PRZM Manual guidance. No snowfall       |
| (SFAC)          |          | observed at San Diego Lindbergh Field   |
|                 |          | (NOWData, NOAA).                        |
+-----------------+----------+-----------------------------------------+
| Minimum Depth   | 32.5 cm  | PRZM Manual Figure 5.2 (EPA, 1998)      |
| of              |          |                                         |
|                 |          | Set to guidance default for free        |
| Evaporation     |          | draining soils.                         |
| (ANETD)         |          |                                         |
+-----------------+----------+-----------------------------------------+

+-----------------+--------+-------------------------------------------+
| **Table 2. PRZM |        |                                           |
| 3.12 Erosion    |        |                                           |
| and Landscape   |        |                                           |
| Parameters for  |        |                                           |
| San Diego       |        |                                           |
| County,         |        |                                           |
| California --   |        |                                           |
| Ornamental      |        |                                           |
| Nurseries.**    |        |                                           |
+=================+========+===========================================+
| **Parameter**   | **V    | **Source/Comments**                       |
|                 | alue** |                                           |
+-----------------+--------+-------------------------------------------+
| Method to       | 4      | PRZM Guidance (EPA, 2004)                 |
| Calculate       | (MUSS) |                                           |
| Erosion         |        |                                           |
| (ERFLAG)        |        |                                           |
+-----------------+--------+-------------------------------------------+
| USLE K Factor   | 0.32   | USDA NRCS Soil Data Mart                  |
| (USLEK)         |        | (http://soildatamart.nrcs.usda.gov/)      |
|                 |        |                                           |
|                 |        | Value listed for the soil series Cieneba  |
|                 |        | coarse sandy loam.                        |
+-----------------+--------+-------------------------------------------+
| USLE LS Factor  | 10.3   | LS equation (Haan and Barfield, 1978)     |
| (USLELS)        |        |                                           |
|                 |        | LS value for 22.5 % slope and 400' slope  |
|                 |        | length                                    |
+-----------------+--------+-------------------------------------------+
| USLE P Factor   | 1.0    | Set to 1 for orchards as per PRZM         |
| (USLEP)         |        | Scenario Guidance (EPA, 2004).            |
+-----------------+--------+-------------------------------------------+
| Field Area      | 172 ha | Area of Shipman Reservoir watershed (PRZM |
| (AFIELD)        |        | Guidance, EPA, 2004)                      |
+-----------------+--------+-------------------------------------------+
| NRCS Hyetograph | 1      | PRZM Manual Figure 5.12 (EPA, 1998)       |
| (IREG)          |        |                                           |
+-----------------+--------+-------------------------------------------+
| Slope (SLP)     | 22.5%  | A good portion of the outdoor production  |
|                 |        | is on hillsides with as much as a 35      |
|                 |        | degree slope (J. Bethke, UC Cooperative   |
|                 |        | Extension), but few pesticides are used   |
|                 |        | on steep slopes. Therefore, mid-point for |
|                 |        | the soil series Cieneba coarse sandy loam |
|                 |        | (15-30%) was selected. USDA NRCS Soil     |
|                 |        | Data Mart                                 |
|                 |        | (<http://soildatamart.nrcs.usda.gov/>).   |
|                 |        | PRZM Scenario Guidance (EPA, 2004).       |
+-----------------+--------+-------------------------------------------+
| Hydraulic       | 600 m  | Shipman Reservoir (PRZM Guidance, EPA,    |
| Length (HL)     |        | 2004)                                     |
+-----------------+--------+-------------------------------------------+
| Irrigation Flag | 1      | Year-round irrigation. C. Wilen (UCCE)    |
| (IRFLAG)        |        |                                           |
+-----------------+--------+-------------------------------------------+
| Number range    | 4      | Methods are primarily drip irrigation and |
| CH              | (drip) | most nurseries have on site irrigation    |
| APTERIrrigation |        | specialists (J. Bethke, personal          |
| Type (IRTYP)    |        | communication). Irrigation Guidance for   |
|                 |        | developing PRZM Scenario, Table 3; (June  |
|                 |        | 15, 2005); and C. Wilen (UCCE).           |
+-----------------+--------+-------------------------------------------+
| Leaching Factor | 0      | Default value. Irrigation Guidance for    |
| (FLEACH)        |        | developing PRZM Scenario, Table 3; (June  |
|                 |        | 15, 2005).                                |
+-----------------+--------+-------------------------------------------+
| Fraction of     | 0.5    | Default value. Irrigation Guidance for    |
| Water Capacity  |        | developing PRZM Scenario, Table 3; (June  |
| when Irrigation |        | 15, 2005).                                |
| is Applied      |        |                                           |
| (PCDEPL)        |        |                                           |
+-----------------+--------+-------------------------------------------+
| Maximum Rate at | 0.46   | Default value. Irrigation Guidance for    |
| which           |        | developing PRZM Scenario, Table 1; (June  |
| Irrigation is   |        | 15, 2005). Set based on f= 0 and cropping |
| Applied         |        | curve number of 82.                       |
| (RATEAP)        |        |                                           |
+-----------------+--------+-------------------------------------------+

+-----------------+--------+-------------------------------------------+
| **Table 3. PRZM |        |                                           |
| 3.12 Crop       |        |                                           |
| Parameters for  |        |                                           |
| San Diego       |        |                                           |
| County,         |        |                                           |
| California --   |        |                                           |
| Ornamental      |        |                                           |
| Nurseries.**    |        |                                           |
+=================+========+===========================================+
| **Parameter**   | **V    | **Source/Comments**                       |
|                 | alue** |                                           |
+-----------------+--------+-------------------------------------------+
| Initial Crop    | 1      | Default value                             |
| (INICRP)        |        |                                           |
+-----------------+--------+-------------------------------------------+
| Initial Surface | 1      | 1 = fallow. Many nurseries lay down       |
| Condition       |        | gravel under the containers. J. Bethke,   |
|                 |        | UC Cooperative Extension, Farm            |
| (ISCOND)        |        | Advisor-Nurseries and Floriculture. This  |
|                 |        | condition is more representative of       |
|                 |        | fallow.                                   |
+-----------------+--------+-------------------------------------------+
| Number of       | 1      | Set to number of crops in simulation.     |
| Different Crops |        | Default value.                            |
| (NDC)           |        |                                           |
+-----------------+--------+-------------------------------------------+
| Number of       | 30     | Set to weather data in meteorological     |
| Cropping        |        | file: San Diego, CA (W23188)              |
| Periods (NCPDS) |        |                                           |
+-----------------+--------+-------------------------------------------+
| Maximum         | 0.1    | Table 5-4 PRZM manual, light density      |
| rainfall        |        | crops (EPA, 1998).                        |
| interception    |        |                                           |
| storage of crop |        |                                           |
| (CINTCP)        |        |                                           |
+-----------------+--------+-------------------------------------------+
| Maximum Active  | 0 cm   | Set to zero to simulate container grown   |
| Root Depth      |        | operations. The majority of southern      |
| (AMXDR)         |        | California's nursery operations are       |
|                 |        | containerized (C. Wilen, UC Cooperative   |
|                 |        | Extension, IPM advisor for Ornamental     |
|                 |        | Nurseries).                               |
+-----------------+--------+-------------------------------------------+
| Maximum Canopy  | 60%    | Based on high-resolution color aerial     |
| Coverage        |        | photography of ornamental nurseries in    |
| (COVMAX)        |        | San Diego County.                         |
+-----------------+--------+-------------------------------------------+
| Maximum Canopy  | 183 cm | Height varies widely as many different    |
| Height (HTMAX)  | (6ft)  | cultivars are grown. Value selected to    |
|                 |        | represent typical fruit or nut tree at    |
|                 |        | sale.                                     |
+-----------------+--------+-------------------------------------------+
| Soil Surface    | 1      | 1 = fallow. Many nurseries lay down       |
| Condition After |        | gravel under the containers. J. Bethke,   |
| Harvest (ICNAH) |        | UC Cooperative Extension, Farm            |
|                 |        | Advisor-Nurseries and Floriculture. This  |
|                 |        | condition is more representative of       |
|                 |        | fallow.                                   |
+-----------------+--------+-------------------------------------------+
| Date of Crop    | 01     | James Bethke, UC Cooperative Extension,   |
| Emergence       | /03/61 | Farm Advisor-Nurseries and Floriculture.  |
|                 |        | Values are set to keep E/T and canopy     |
| (EMD, EMM,      |        | coverage terms working correctly for this |
| IYREM)          |        | deciduous scenario. Set to typical leaf   |
|                 |        | bloom dates (March 1). Adjusted to the    |
|                 |        | nearest corresponding RUSLE date (RUSLE   |
|                 |        | Project; C25CBCBC).                       |
+-----------------+--------+-------------------------------------------+
| Date of Crop    | 01     | Values are set to keep E/T and canopy     |
| Maturity        | /04/61 | coverage terms working correctly for this |
|                 |        | deciduous scenario. Set to 1 month post   |
| (MAD, MAM,      |        | leaf bloom.                               |
| IYRMAT)         |        |                                           |
+-----------------+--------+-------------------------------------------+
| Date of Crop    | 01     | James Bethke, UC Cooperative Extension,   |
| Harvest (HAD,   | /11/61 | Farm Advisor-Nurseries and Floriculture.  |
| HAM, IYRHAR)    |        | Values are set to keep E/T and canopy     |
|                 |        | coverage terms working correctly for this |
|                 |        | deciduous scenario. Set to typical        |
|                 |        | leaf-off dates.                           |
+-----------------+--------+-------------------------------------------+
| Maximum Dry     | 0.0    | Not used in scenario                      |
| Weight (WFMAX)  |        |                                           |
+-----------------+--------+-------------------------------------------+
| SCS Curve       | 82,    | TR-55, Table 2-2c (USDA 1986). Value for  |
| Number (CN)     | 82, 87 | farmsteads, buildings, lanes, driveways,  |
|                 |        | and surrounding lots. Hydrologic Group C. |
|                 |        | Third curve number represents a cleared   |
|                 |        | condition similar to a gravel road.       |
+-----------------+--------+-------------------------------------------+
| Manning's N     | 0.014  | RUSLE Project; C25CBCBC for San Diego, CA |
| Value (MNGN)    |        | orchards with conventional till and no    |
|                 |        | cover (cover code 6). These data were     |
|                 |        | used to approximate values for nurseries  |
|                 |        | in southern California as no data for     |
|                 |        | ornamental nurseries were included in the |
|                 |        | project.                                  |
+-----------------+--------+-------------------------------------------+
| USLE C Factor   | 0      | RUSLE Project; C25CBCBC for San Diego, CA |
| (USLEC)         | .252 - | orchards with conventional till and no    |
|                 | 0.368  | cover (cover code 6). These data were     |
|                 |        | used to approximate values for nurseries  |
|                 |        | in southern California as no data for     |
|                 |        | ornamental nurseries were included in the |
|                 |        | project. Note: RUSLE dates and C factors  |
|                 |        | from the RUSLE project have been          |
|                 |        | reordered and tied to emergence dates.    |
+-----------------+--------+-------------------------------------------+

+---------------+-------------------+---------------------------------+
| **Table 4.    |                   |                                 |
| PRZM 3.12     |                   |                                 |
| Cieneba       |                   |                                 |
| Coarse Sandy  |                   |                                 |
| Loam Soil     |                   |                                 |
| Parameters    |                   |                                 |
| for San Diego |                   |                                 |
| County,       |                   |                                 |
| California -- |                   |                                 |
| Ornamental    |                   |                                 |
| Nurseries**   |                   |                                 |
+---------------+-------------------+---------------------------------+
| **Parameter** | **Value**         | **Source/Comments**             |
+---------------+-------------------+---------------------------------+
| Total Soil    | 25 cm             | NRCS Soil Data Mart (SDM)       |
| Depth (CORED) |                   | (htt                            |
|               |                   | p://soildatamart.nrcs.usda.gov) |
+---------------+-------------------+---------------------------------+
| Number of     | 2                 | NRCS Soil Data Mart (SDM)       |
| Horizons      |                   | ([http://soi                    |
| (NHORIZ)      |                   | ldatamart.nrcs.usda.gov](http:/ |
|               |                   | /soildatamart.nrcs.usda.gov/)). |
|               |                   | The third horizon from SDM was  |
|               |                   | excluded because it is bedrock. |
+---------------+-------------------+---------------------------------+
| Horizon       | 10 cm (HORIZN =   | NRCS Soil Data Mart (SDM)       |
| Thickness     | 1)                | ([http://soi                    |
| (THKNS)       |                   | ldatamart.nrcs.usda.gov](http:/ |
|               | 15 cm (HORIZN =   | /soildatamart.nrcs.usda.gov/)). |
|               | 2)                |                                 |
+---------------+-------------------+---------------------------------+
| Bulk Density  | 1.55 g/cm^3^      | NRCS Soil Data Mart (SDM)       |
| (BD)          | (HORIZN = 1)      | ([http://soi                    |
|               |                   | ldatamart.nrcs.usda.gov](http:/ |
|               | 1.55 g/cm^3^      | /soildatamart.nrcs.usda.gov/)). |
|               | (HORIZN = 2)      | Midpoint of the reported range. |
|               |                   | PRZM Scenario Guidance (EPA,    |
|               |                   | 2004).                          |
+---------------+-------------------+---------------------------------+
| Initial Water | 0.168 cm^3^/cm^3^ | NRCS Soil Data Mart (SDM);      |
| Content       | (HORIZN =1)       | values are mean 1/3-bar water   |
| (THETO)       |                   | contents of Cieneba coarse      |
|               | 0.168 cm^3^/cm^3^ | sandy loam soils.               |
|               | (HORIZN =2)       |                                 |
+---------------+-------------------+---------------------------------+
| Compartment   | 0.1 cm (HORIZN =  | NRCS Soil Data Mart (SDM)       |
| Thickness     | 1)                | ([http://soi                    |
| (DPN)         |                   | ldatamart.nrcs.usda.gov](http:/ |
|               | 5.0 cm (HORIZN =  | /soildatamart.nrcs.usda.gov/)). |
|               | 2)                | PRZM Scenario Guidance (EPA,    |
|               |                   | 2004).                          |
+---------------+-------------------+---------------------------------+
| Field         | 0.168 cm^3^/cm^3^ | NRCS Soil Data Mart (SDM);      |
| Capacity      | (HORIZN =1)       | values are mean 1/3-bar water   |
| (THEFC)       |                   | contents of Cieneba coarse      |
|               | 0.168 cm^3^/cm^3^ | sandy loam soils.               |
|               | (HORIZN =2)       |                                 |
+---------------+-------------------+---------------------------------+
| Wilting Point | 0.08 cm^3^/cm^3^  | NRCS Soil Data Mart (SDM);      |
| (THEWP)       | (HORIZN =1)       | values are mean 15-bar water    |
|               |                   | contents of Cieneba coarse      |
|               | 0.08 cm^3^/cm^3^  | sandy loam soils.               |
|               | (HORIZN =2)       |                                 |
+---------------+-------------------+---------------------------------+
| Organic       | 0.44 % (HORIZN =  | NRCS SDM; values for horizons 1 |
| Carbon        | 1)                | to 3 = mean %OM / 1.724. PRZM   |
| Content (OC)  |                   | Scenario Guidance (EPA, 2004).  |
|               | 0.44 % (HORIZN =  |                                 |
|               | 2)                |                                 |
+---------------+-------------------+---------------------------------+

***Sensitive Parameter Uncertainties***

[Meteorological File]{.underline}

As characterized above, Metfile W23188 (San Diego, CA) is the closest
metfile to San Diego County, which was used to represent this scenario.
The metfile is located approximately 28 miles from the center of San
Diego County and is generally representative of the area. However, the
terrain is mountainous and elevations vary widely. The metstation is
located near sea level (4 meters AMSL). Rainfall in southern California
may be over or underestimated by this station due to terrain and
orographic effects. A sensitivity analysis of meteorological stations in
the surrounding region would reduce uncertainty in the PRZM results.

[Slope]{.underline}

The scenario USLELS value was calculated with the Haan and Barfield
equation (1978) using a 22.5% slope and an assumed 400-foot slope
length, as per PRZM scenario development guidance (EPA, 2004). Nurseries
in southern California are sometimes located on hillsides with as much
as a 35 degree slope (J. Bethke, UC Cooperative Extension), but few
pesticides are used on steep slopes. Therefore, mid-point for the soil
series Cieneba coarse sandy loam (15-30%) was selected based on PRZM
Scenario Guidance (EPA, 2004). This scenario may underestimate runoff
and erosion for nurseries located on slopes greater than 22.5%

[USLE C Factor and Manning's N Value]{.underline}

The RUSLE Project does not include data for ornamental nursery crops.
Therefore, USLE C Factor and Manning's N values were selected from data
on California orchards conventional till and no cover. This involves
some uncertainty since many nurseries create a surface layer of gravel
or cloth. Of the available locations, San Diego California has the most
similar meteorological conditions and no cover as this scenario.

[Soil Data]{.underline}

No geospatial data were available to determine the exact locations and
geographic extent of nurseries in the region. The USGS GIRAS
Landuse/Landcover data (EPA, 1994) for the Conterminous United States
includes a nurseries classification; however the data are generally 25
years old at the time of this scenario development and preliminary
review of the data indicates that nurseries are not well represented.
This is likely due to the resolution of the data (30 m) and age of the
data set (based on 1970's and 80's imagery). As a result, soils were
selected based on soil recommendations of local experts, the geographic
extent of the listed soils in the area, the drainage group, slope, and
erodibility. The soil selected is a hydrologic group C soil.

[Crop Parameters]{.underline}

Outdoor ornamental nurseries are highly diverse in the numbers, sizes,
and types of plants grown. Ornamental nurseries also vary in the
cultivation methods which can range from potted plants (container
operations) to field nurseries that may harvest and package plants as
bare root or balled and burlapped. This scenario has been parameterized
to be representative of the most "typical" nursery plants in the area
(see description above). Runoff and erosion may be over or
underestimated depending on the type of nursery modeled and a
sensitivity analysis has high value in this regard.

[Curve Number]{.underline}

The curve number is the most sensitive parameter in PRZM scenarios. The
curve number for this scenario was based on TR-55 (Table 2-2c).
Nurseries can be covered in roads, wooded areas, field borders, and
buildings. Therefore the curve number closest to this scenario was the
value for a hydrologic group C soil representative of farmsteads,
buildings, lanes, driveways, and surrounding lots. Runoff and erosion
may be under or over-estimated for alternative nursery operations and
model validation has high value in this regard. Based on preliminary
investigation, no runoff data are available for validating runoff from
outdoor nursery operations in this geographic area.

![](media/image1.png){width="9.129166666666666in"
height="5.352083333333334in"}

**Figure 1. TR-55 (USDA, 1986) Farmstead curve number used for scenario
development relative to other available cover types, soil treatments,
and conditions.**

<table style="width:100%;">
<colgroup>
<col style="width: 16%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 7%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="11"><strong>Table 5. Soils of San Diego County, California
Ranked by Area<sup>a,b</sup>. Includes Soils Comprising Greater than 1%
of Total Soil Acres.</strong></td>
</tr>
<tr class="even">
<td><strong>Soil</strong></td>
<td><strong>Total Acres</strong></td>
<td><strong>%<br />
Area</strong></td>
<td><strong>Hydrologic Group</strong></td>
<td><strong>Erodibility</strong></td>
<td><strong>Slope</strong></td>
<td><strong>pH</strong></td>
<td><strong>OM</strong></td>
<td><strong>Sand</strong></td>
<td><strong>Silt</strong></td>
<td><strong>Clay</strong></td>
</tr>
<tr class="odd">
<td>CIENEBA</td>
<td>332986</td>
<td>16.5%</td>
<td>C</td>
<td>0.24-0.32</td>
<td>9-75</td>
<td>5.8-6.5</td>
<td>0.75</td>
<td>67.9-68.5</td>
<td>19-19.6</td>
<td>12.5</td>
</tr>
<tr class="even">
<td>TOLLHOUSE</td>
<td>131885</td>
<td>6.5%</td>
<td>D</td>
<td>0.24</td>
<td>9-65</td>
<td>6.7</td>
<td>1.5</td>
<td>65.2</td>
<td>23.3</td>
<td>11.5</td>
</tr>
<tr class="odd">
<td>FALLBROOK</td>
<td>127959</td>
<td>6.3%</td>
<td>B</td>
<td>0.24-0.28</td>
<td>2-50</td>
<td>6.1-6.7</td>
<td>0.75-1.25</td>
<td>65.9-68.8</td>
<td>16.2-19.6</td>
<td>13-15</td>
</tr>
<tr class="even">
<td>SHEEPHEAD</td>
<td>106947</td>
<td>5.3%</td>
<td>C</td>
<td>0.17</td>
<td>9-65</td>
<td>6.3</td>
<td>2</td>
<td>63.5</td>
<td>26.5</td>
<td>10</td>
</tr>
<tr class="odd">
<td>LA POSTA</td>
<td>106823</td>
<td>5.3%</td>
<td>B</td>
<td>0.17</td>
<td>5-65</td>
<td>6.7</td>
<td>2</td>
<td>81.9</td>
<td>10.6</td>
<td>7.5</td>
</tr>
<tr class="even">
<td>LAS POSAS</td>
<td>85559</td>
<td>4.2%</td>
<td>C</td>
<td>0.32</td>
<td>2-65</td>
<td>7</td>
<td>0.75</td>
<td>63.1</td>
<td>19.4</td>
<td>17.5</td>
</tr>
<tr class="odd">
<td>REDDING</td>
<td>66957</td>
<td>3.3%</td>
<td>D</td>
<td>0.32</td>
<td>2-50</td>
<td>5.6</td>
<td>1.25</td>
<td>43</td>
<td>39.5</td>
<td>17.5</td>
</tr>
<tr class="even">
<td>VISTA</td>
<td>62783</td>
<td>3.1%</td>
<td>B</td>
<td>0.24-0.28</td>
<td>5-65</td>
<td>6.7</td>
<td>0.75-1.25</td>
<td>65.4-66.8</td>
<td>22.2-23.6</td>
<td>11</td>
</tr>
<tr class="odd">
<td>CROUCH</td>
<td>61952</td>
<td>3.1%</td>
<td>B</td>
<td>0.17-0.2</td>
<td>8-75</td>
<td>6.3</td>
<td>2</td>
<td>63.9-66.5</td>
<td>24-26.6</td>
<td>9.5</td>
</tr>
<tr class="even">
<td>HUERHUERO</td>
<td>53158</td>
<td>2.6%</td>
<td>D</td>
<td>0.37</td>
<td>2-30</td>
<td>5.6</td>
<td>1.5</td>
<td>42.1</td>
<td>37.9</td>
<td>20</td>
</tr>
<tr class="odd">
<td>SAN MIGUEL</td>
<td>52442</td>
<td>2.6%</td>
<td>D</td>
<td>0.64</td>
<td>9-30</td>
<td>5.6</td>
<td>0.75</td>
<td>30.1</td>
<td>54.9</td>
<td>15</td>
</tr>
<tr class="even">
<td>DIABLO</td>
<td>47441</td>
<td>2.4%</td>
<td>D</td>
<td>0.17</td>
<td>2-50</td>
<td>7.2</td>
<td>2</td>
<td>22.1-23.3</td>
<td>27.9-29.2</td>
<td>47.5-50</td>
</tr>
<tr class="odd">
<td>ROSITAS</td>
<td>46567</td>
<td>2.3%</td>
<td>A</td>
<td>0.17-0.24</td>
<td>0-15</td>
<td>8.2</td>
<td>0.25</td>
<td>80.2-96.8</td>
<td>0.7-17.3</td>
<td>2.5</td>
</tr>
<tr class="even">
<td>BANCAS</td>
<td>45751</td>
<td>2.3%</td>
<td>B</td>
<td>0.24</td>
<td>5-65</td>
<td>6.7</td>
<td>1.5-2</td>
<td>42.1</td>
<td>37.9</td>
<td>20</td>
</tr>
<tr class="odd">
<td>VISALIA</td>
<td>45088</td>
<td>2.2%</td>
<td>B</td>
<td>0.2</td>
<td>0-15</td>
<td>6.3</td>
<td>2.5</td>
<td>67.4</td>
<td>19.6</td>
<td>13</td>
</tr>
<tr class="even">
<td>HOLLAND</td>
<td>44735</td>
<td>2.2%</td>
<td>B/C</td>
<td>0.24</td>
<td>2-60</td>
<td>5.8</td>
<td>3</td>
<td>62.8-66.1</td>
<td>19.9-26.2</td>
<td>11-14</td>
</tr>
<tr class="odd">
<td>FRIANT</td>
<td>43688</td>
<td>2.2%</td>
<td>D</td>
<td>0.2</td>
<td>9-70</td>
<td>6.3</td>
<td>1.5</td>
<td>66.1</td>
<td>19.9</td>
<td>14</td>
</tr>
<tr class="even">
<td>MOTTSVILLE</td>
<td>42838</td>
<td>2.1%</td>
<td>A/D</td>
<td>0.24</td>
<td>0-15</td>
<td>6.3</td>
<td>2</td>
<td>82.8</td>
<td>10.7</td>
<td>6.5</td>
</tr>
<tr class="odd">
<td>OLIVENHAIN</td>
<td>41806</td>
<td>2.1%</td>
<td>D</td>
<td>0.32-0.37</td>
<td>2-50</td>
<td>5.8</td>
<td>0.75</td>
<td>42.1</td>
<td>37.9</td>
<td>20</td>
</tr>
<tr class="even">
<td>LAS FLORES</td>
<td>32818</td>
<td>1.6%</td>
<td>D</td>
<td>0.37</td>
<td>2-30</td>
<td>6.1</td>
<td>0.75</td>
<td>86.8</td>
<td>6.7</td>
<td>6.5</td>
</tr>
<tr class="odd">
<td>CARRIZO</td>
<td>30347</td>
<td>1.5%</td>
<td>A</td>
<td>0.24</td>
<td>0-9</td>
<td>7.9</td>
<td>0.25</td>
<td>96</td>
<td>1.5</td>
<td>2.5</td>
</tr>
<tr class="even">
<td>PLACENTIA</td>
<td>30231</td>
<td>1.5%</td>
<td>D</td>
<td>0.37</td>
<td>0-15</td>
<td>6.1</td>
<td>1.25</td>
<td>65.1</td>
<td>18.9</td>
<td>16</td>
</tr>
<tr class="odd">
<td>TUJUNGA</td>
<td>27553</td>
<td>1.4%</td>
<td>A</td>
<td>0.15</td>
<td>0-5</td>
<td>7</td>
<td>0.75</td>
<td>96</td>
<td>1.5</td>
<td>2.5</td>
</tr>
<tr class="even">
<td>RAMONA</td>
<td>26131</td>
<td>1.3%</td>
<td>B</td>
<td>0.37</td>
<td>0-30</td>
<td>6.1</td>
<td>0.75</td>
<td>68.5</td>
<td>24</td>
<td>7.5</td>
</tr>
<tr class="odd">
<td>RIVERWASH</td>
<td>22131</td>
<td>1.1%</td>
<td>D</td>
<td>0.1-0.17</td>
<td>0-5</td>
<td>-</td>
<td>0.05</td>
<td>92.9-97.9</td>
<td>1.6-6.6</td>
<td>0.5</td>
</tr>
<tr class="even">
<td colspan="11"><p>Notes:</p>
<p><sup>a</sup> pH, OM, Sand, Silt, and Clay are based on representative
values from USDA Soil Data Mart.</p>
<p><sup>b</sup> Table excludes soils less than 1% of total soil area.
Areas such as gravel pits, urban land, lagoons, etc were not included in
the % area computations. Also excludes areas not yet complete in soil
data mart.</p></td>
</tr>
</tbody>
</table>

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**Contacts**

**James A. Bethke**

UC Cooperative Extension, Farm Advisor-Nurseries and Floriculture

334 Via Vera Cruz, Suite 152

San Marcos, CA 92078

Phone: 760-752-4715

Fax: 760-752-4725

Email: <bethke@ucr.edu>

**Cheryl Wilen, Ph.D.**

Area Integrated Pest Management Advisor

Los Angeles, Orange, and San Diego Counties

5555 Overland Ave

Suite 4101, Bldg 4

San Diego, CA 92123-1219

Phone: (858) 694-2845

Email: <cawilen@ucdavis.edu>