Soil pH in Riverside, CA: Lime or Sulfur?

Typical topsoil pH in Riverside, CA

Typical topsoil in Riverside, CA is pH 7.15, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Riverside needs, by plant

• Just outside, test first: lawn (cool-season grass) (off by 0.2), vegetable garden (off by 0.2), roses (off by 0.2).
• Beds or pots instead: tomatoes, potatoes, strawberries, blueberries, azaleas and rhododendrons, blue hydrangeas, pink hydrangeas.

What to do next

If your test lands near 7.15, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, roses.

How mixed the soil is

Of the 1,160,828 surveyed acres in Riverside, CA, 47% are near neutral (6.5-7.3), 36% are alkaline (above 7.3), 17% are moderately acidic (5.5-6.5). Mapped soils run from pH 5.6 to 8.9, a spread of 3.3 units across 533 soil components. No single class covers 60% of the county, so two gardens a few miles apart here can need opposite treatments. Test your own bed.

Clay, organic matter and rates

Topsoil here averages 13.3% clay and 1.04% 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. 33% of mapped components carry free carbonate (lime already in the ground), enough that sulfur gets neutralised before it does much.

Riverside against the rest of California

pH 7.15 is 0.61 above the California median of 6.54. 49 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: Modoc (7.04), Sutter (7.1), Orange (7.12), San Luis Obispo (7.12), Ventura (7.22), Merced (7.27), Tulare (7.27), Kern (7.49).

The range in California runs from Del Norte at 5.43 to Imperial at 8.16; Riverside sits 63% of the way up.