Soil pH in Wahkiakum, WA: Lime or Sulfur?

Typical topsoil pH in Wahkiakum, WA

Typical topsoil in Wahkiakum, WA is pH 5.05, too acidic for vegetable garden. Expect roughly 17.3 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Wahkiakum needs, by plant

• Already in range: potatoes, blueberries, azaleas and rhododendrons, blue hydrangeas.
• Lime: lawn (cool-season grass) 17.3 lb/100 sq ft over 4 applications; vegetable garden 17.3 lb/100 sq ft over 4 applications; tomatoes 17.3 lb/100 sq ft over 4 applications; strawberries 11.5 lb/100 sq ft over 3 applications; roses 17.3 lb/100 sq ft over 4 applications; pink hydrangeas 13.8 lb/100 sq ft over 3 applications.

What to do next

If your test confirms pH near 5.05, spread about 173 lb of ground limestone per 1,000 sq ft of vegetable bed in 4 doses, ideally in fall.

How mixed the soil is

Of the 153,848 surveyed acres in Wahkiakum, WA, 74% are strongly acidic (below 5.5), 26% are moderately acidic (5.5-6.5). Mapped soils run from pH 4.3 to 7, a spread of 2.7 units across 45 soil components. 74% 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 16.4% clay and 10.46% organic matter, which this site treats as clay. At 10.46% organic matter the soil buffers like a heavier one, which pushes it into the clay bracket. Moving it one pH unit takes about 11.5 lb of lime or 3.4 lb of sulfur per 100 sq ft. None of the mapped components carry free carbonate.

Wahkiakum against the rest of Washington

pH 5.05 is 1.36 below the Washington median of 6.41. 2 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: Grays Harbor (4.93), Pacific (4.99), Lewis (5.08), Clallam (5.23), Jefferson (5.24), Mason (5.4).

The range in Washington runs from Grays Harbor at 4.93 to Adams at 7.45; Wahkiakum sits 5% of the way up.