Soil pH in Siskiyou, CA: Lime or Sulfur?

Typical topsoil pH in Siskiyou, CA

Typical topsoil in Siskiyou, CA is pH 6.75, already right for vegetable garden (6-7). Test before adding anything.

What Siskiyou needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, tomatoes, roses.
• Sulfur: potatoes 3 lb/100 sq ft over 2 applications; strawberries 1.8 lb/100 sq ft; blueberries 4.1 lb/100 sq ft over 3 applications; azaleas and rhododendrons 3.5 lb/100 sq ft over 2 applications; blue hydrangeas 3.5 lb/100 sq ft over 2 applications; pink hydrangeas 1.2 lb/100 sq ft.

What to do next

If your test lands near 6.75, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, roses.

How mixed the soil is

Of the 1,022,857 surveyed acres in Siskiyou, CA, 56% are near neutral (6.5-7.3), 25% are moderately acidic (5.5-6.5), 17% are alkaline (above 7.3), 1% are strongly acidic (below 5.5). Mapped soils run from pH 5.3 to 9, a spread of 3.7 units across 385 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 18.4% clay and 3.41% 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. 9% of mapped components carry free carbonate (lime already in the ground).

Siskiyou against the rest of California

pH 6.75 is 0.21 above the California median of 6.54. 35 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: Santa Barbara (6.69), Sierra (6.71), Los Angeles (6.72), Fresno (6.75), Lassen (6.77), Mono (6.79), Alameda (6.81), Monterey (6.81).

The range in California runs from Del Norte at 5.43 to Imperial at 8.16; Siskiyou sits 48% of the way up.