Soil pH in San Diego, CA: Lime or Sulfur?

Typical topsoil pH in San Diego, CA

Typical topsoil in San Diego, CA is pH 6.46, already right for vegetable garden (6-7). Test before adding anything.

What San Diego needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, tomatoes, strawberries, roses, pink hydrangeas.
• Sulfur: potatoes 2.3 lb/100 sq ft over 2 applications; blueberries 3.5 lb/100 sq ft over 2 applications; azaleas and rhododendrons 2.8 lb/100 sq ft over 2 applications; blue hydrangeas 2.8 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 6.46, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, strawberries, roses, pink hydrangeas.

How mixed the soil is

Of the 1,165,357 surveyed acres in San Diego, CA, 60% are moderately acidic (5.5-6.5), 28% are near neutral (6.5-7.3), 11% are alkaline (above 7.3). Mapped soils run from pH 5.6 to 8.2, a spread of 2.6 units across 270 soil components. 60% of the land falls in one class, so the county figure is a fair first guess for most yards here.

Clay, organic matter and rates

Topsoil here averages 14.4% clay and 1.23% organic matter, which this site treats as loam. Moving it one pH unit takes about 7 lb of lime or 2.3 lb of sulfur per 100 sq ft. 11% of mapped components carry free carbonate (lime already in the ground).

San Diego against the rest of California

pH 6.46 is 0.08 below the California median of 6.54. 27 of 58 California counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Napa (6.37), Plumas (6.4), Santa Cruz (6.42), Santa Clara (6.44), San Francisco (6.5), Madera (6.58), Solano (6.63), Contra Costa (6.69).

The range in California runs from Del Norte at 5.43 to Imperial at 8.16; San Diego sits 38% of the way up.