Soil series profile

Rositas soil series

Rositas is a somewhat excessively drained soil with a loamy fine sand surface, mapped on 784,663 acres in 11 counties across 3 states. Hydrologic group A.

#279 by mapped area Typic Torripsamments (Entisols)

Drainage class: Somewhat excessively drained
Hydrologic group: A
Typical topsoil pH: 8.0
Mapped area: 785k

Typical Rositas profile

Texture and pH by depth

Depth to scale. More strongly shaded layers hold more clay. Horizon names are the soil survey's (A = topsoil, B = subsoil, C = parent material).

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Typical Rositas horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–4 in (C1)	Loamy fine sand	8.0	5%	85%	0.2%
4–60 in (C2)	Fine sand	8.0	3%	92%	0.2%

Representative values from the most extensive Rositas map unit (Rositas loamy fine sand, 0 to 2 percent slopes, survey area CA683). Other map units of this series vary within the series range.

Stock photo for illustration, not a sample of this soil series. Credit on the Sources & method page.

What this means

What Rositas soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Rositas soils is moderately alkaline: pH 8.0 (most land between 7.8 and 8.2). Acid-loving plants such as blueberries and azaleas struggle without amended beds, and some trees and shrubs show iron chlorosis (yellow leaves with green veins).

Sandy topsoil covers 98% of mapped Rositas acres. It drains fast and warms early in spring, but dries out and loses nutrients quickly: mulch, compost and steady watering help. The most common surface texture is sand (37% of mapped Rositas acres).

97% of mapped Rositas acres is excessively or somewhat excessively drained: water moves through fast, so gardens need more frequent watering in dry spells.

For lawns and yards

98% of mapped acres is in hydrologic group A, where water soaks in fast. Lawns there dry out quickly; deeper, less frequent watering and organic matter help.

For a septic system

For conventional septic absorption fields, NRCS rates 91% of the acres in mapped Rositas soils very limited, <1% somewhat limited and 8% not limited.

Where the soil is very limited (slow permeability, a high water table, flooding, shallow bedrock or steep slopes), alternative systems such as mound or sand-filter designs are common and cost more.

Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.

Generated from the mapped numbers above using fixed rules, not a site visit. See how these notes are written.

Where Rositas soil is found

Mapped acres

Rositas is mapped in California, Arizona and Nevada.

Counties with the most mapped Rositas soil
County	Acres	Share of county land
Imperial County, CA	267,036	18.2%
Maricopa County, AZ	149,780	2.4%
Yuma County, AZ	87,834	4.0%
San Diego County, CA	42,622	1.8%
Riverside County, CA	29,486	1.0%
Pima County, AZ	15,939	0.3%
La Paz County, AZ	14,167	0.5%
Mohave County, AZ	10,533	0.1%
Pinal County, AZ	10,468	0.3%
San Bernardino County, CA	5,697	0.1%
Clark County, NV	4,669	0.1%

Septic absorption fields

NRCS rating, share of Rositas acres

Not limited 8%

Somewhat limited <1%

Very limited 91%

Not rated <1%

Septic tank absorption field rating across mapped Rositas acres. Scale 0 to 100% of mapped land.

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Septic tank absorption field rating across mapped Rositas acres.
Category	Share of acres
Not limited	8.3%
Somewhat limited	0.2%
Very limited	91.0%
Not rated	0.4%

Drainage, water table and flooding

Share of Rositas acres

Depth to seasonal high water table: About 2.9 feet (35 in) (median where reported); within 18 inches on <1% of acres.
Flooding: Mapped as flooding on 1% of acres (0% occasional, <1% frequent).
Slope: Typically 1–10% (median 5%).
Topsoil organic matter: Median 0.2%.

Drainage class

Excessively drained 6%

Somewhat excessively drained 91%

Well drained <1%

Moderately well drained 0%

Somewhat poorly drained 3%

Poorly drained 0%

Very poorly drained 0%

Not rated <1%

Drainage class across mapped Rositas acres. Scale 0 to 100% of mapped land.

Show as a table

Drainage class across mapped Rositas acres.
Category	Share of acres
Excessively drained	5.9%
Somewhat excessively drained	90.9%
Well drained	0.3%
Moderately well drained	0.0%
Somewhat poorly drained	2.5%
Poorly drained	0.0%
Very poorly drained	0.0%
Not rated	0.4%

Hydrologic soil group

A: fast infiltration (mostly sandy or gravelly) 98%

B: moderate infiltration 0%

C: slow infiltration 1%

D: very slow infiltration (clayey, shallow or wet) 0%

A/D: D as is, A if drained 0%

B/D: D as is, B if drained 0%

C/D: D as is, C if drained 0%

Not rated <1%

Hydrologic soil group across mapped Rositas acres. Scale 0 to 100% of mapped land.

Show as a table

Hydrologic soil group across mapped Rositas acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	98.2%
B: moderate infiltration	0.0%
C: slow infiltration	1.3%
D: very slow infiltration (clayey, shallow or wet)	0.0%
A/D: D as is, A if drained	0.0%
B/D: D as is, B if drained	0.0%
C/D: D as is, C if drained	0.0%
Not rated	0.4%

Sources & data dates

Source: USDA NRCS Soil Survey Geographic Database (SSURGO), queried through Soil Data Access. Public domain.
Data date: SSURGO as published on November 3, 2026 (most recent survey area update October 26, 2026). NRCS refreshes SSURGO each October.
Scope: All map unit components named Rositas (component kind "Series") in SSURGO: 784,663 acres.
Method: Shares are by mapped acres of Rositas components. The profile comes from the single largest Rositas component. Full methodology.

Independent reference site. No government affiliation or endorsement.

Full narrative description: USDA Official Soil Series Description for Rositas.