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

Typical topsoil pH in San Mateo, CA

Typical topsoil in San Mateo, CA is pH 6.26, already right for vegetable garden (6-7). Test before adding anything.

What San Mateo needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, tomatoes, strawberries, roses, pink hydrangeas.
• Sulfur: potatoes 1.8 lb/100 sq ft; blueberries 3 lb/100 sq ft over 2 applications; azaleas and rhododendrons 2.3 lb/100 sq ft over 2 applications; blue hydrangeas 2.3 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 6.26, 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 180,413 surveyed acres in San Mateo, CA, 70% are moderately acidic (5.5-6.5), 17% are near neutral (6.5-7.3), 7% are alkaline (above 7.3), 6% are strongly acidic (below 5.5). Mapped soils run from pH 5 to 8.5, a spread of 3.5 units across 375 soil components. 70% 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 22.4% clay and 2.75% 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. None of the mapped components carry free carbonate.

San Mateo against the rest of California

pH 6.26 is 0.28 below the California median of 6.54. 17 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: Calaveras (6.17), Shasta (6.17), Tehama (6.2), Yuba (6.25), Butte (6.27), Lake (6.28), Sacramento (6.29), Trinity (6.29).

The range in California runs from Del Norte at 5.43 to Imperial at 8.16; San Mateo sits 30% of the way up.