Soil pH in Skamania, WA: Lime or Sulfur?

Typical topsoil pH in Skamania, WA

Typical topsoil in Skamania, WA is pH 5.86, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Skamania needs, by plant

• Already in range: potatoes, strawberries, azaleas and rhododendrons.
• Just outside, test first: lawn (cool-season grass) (off by 0.1), vegetable garden (off by 0.1), roses (off by 0.1), pink hydrangeas (off by 0.1).
• Lime: tomatoes 4.2 lb/100 sq ft.
• Sulfur: blueberries 2.1 lb/100 sq ft over 2 applications; blue hydrangeas 1.4 lb/100 sq ft.

What to do next

If your test lands near 5.86, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, potatoes, strawberries, roses, azaleas and rhododendrons, pink hydrangeas.

How mixed the soil is

Of the 343,244 surveyed acres in Skamania, WA, 65% are moderately acidic (5.5-6.5), 21% are strongly acidic (below 5.5), 14% are near neutral (6.5-7.3). Mapped soils run from pH 5 to 7.2, a spread of 2.2 units across 218 soil components. 65% 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 14.3% clay and 3.31% 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.

Skamania against the rest of Washington

pH 5.86 is 0.55 below the Washington median of 6.41. 18 of 39 Washington counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Island (5.67), Snohomish (5.68), Cowlitz (5.74), Thurston (5.76), Spokane (6.41), Okanogan (6.45), Kittitas (6.47), Pend Oreille (6.49).

The range in Washington runs from Grays Harbor at 4.93 to Adams at 7.45; Skamania sits 37% of the way up.