Soil pH in Orange, CA: Lime or Sulfur?

Typical topsoil pH in Orange, CA

Typical topsoil in Orange, CA is pH 7.12, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Orange needs, by plant

• Just outside, test first: lawn (cool-season grass) (off by 0.1), vegetable garden (off by 0.1), roses (off by 0.1).
• Beds or pots instead: tomatoes, potatoes, strawberries, blueberries, azaleas and rhododendrons, blue hydrangeas, pink hydrangeas.

What to do next

If your test lands near 7.12, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, roses.

How mixed the soil is

Of the 413,106 surveyed acres in Orange, CA, 41% are alkaline (above 7.3), 38% are near neutral (6.5-7.3), 21% are moderately acidic (5.5-6.5). Mapped soils run from pH 4 to 9, a spread of 5 units across 208 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 20.6% clay and 1.35% 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. 39% of mapped components carry free carbonate (lime already in the ground), enough that sulfur gets neutralised before it does much.

Orange against the rest of California

pH 7.12 is 0.58 above the California median of 6.54. 47 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: Yolo (6.9), Stanislaus (6.96), Modoc (7.04), Sutter (7.1), San Luis Obispo (7.12), Riverside (7.15), Ventura (7.22), Merced (7.27).

The range in California runs from Del Norte at 5.43 to Imperial at 8.16; Orange sits 62% of the way up.