Soil pH in Modoc, CA: Lime or Sulfur?

Typical topsoil pH in Modoc, CA

Typical topsoil in Modoc, CA is pH 7.04, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Modoc needs, by plant

• Just outside, test first: lawn (cool-season grass) (off by 0), vegetable garden (off by 0), tomatoes (off by 0.2), roses (off by 0).
• Sulfur: potatoes 3.5 lb/100 sq ft over 2 applications; strawberries 2.3 lb/100 sq ft over 2 applications; blueberries 4.6 lb/100 sq ft over 3 applications; azaleas and rhododendrons 4.1 lb/100 sq ft over 3 applications; blue hydrangeas 4.1 lb/100 sq ft over 3 applications; pink hydrangeas 1.8 lb/100 sq ft.

What to do next

If your test lands near 7.04, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, roses.

How mixed the soil is

Of the 960,106 surveyed acres in Modoc, CA, 63% are near neutral (6.5-7.3), 23% are alkaline (above 7.3), 15% are moderately acidic (5.5-6.5). Mapped soils run from pH 5.6 to 9.6, a spread of 4 units across 1,165 soil components. 63% 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 21.2% clay and 2.59% 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. 13% of mapped components carry free carbonate (lime already in the ground).

Modoc against the rest of California

pH 7.04 is 0.5 above the California median of 6.54. 45 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: San Joaquin (6.81), Colusa (6.89), Yolo (6.9), Stanislaus (6.96), Sutter (7.1), Orange (7.12), San Luis Obispo (7.12), Riverside (7.15).

The range in California runs from Del Norte at 5.43 to Imperial at 8.16; Modoc sits 59% of the way up.