Soil pH in Cowlitz, WA: Lime or Sulfur?
Typical topsoil pH in Cowlitz, WA
Typical topsoil in Cowlitz, WA is pH 5.74, too acidic for vegetable garden. Expect roughly 9.2 lb of lime per 100 sq ft, but only after a soil test confirms it.
What Cowlitz needs, by plant
- Already in range: potatoes, strawberries, azaleas and rhododendrons.
- Just outside, test first: blueberries (off by 0.2), blue hydrangeas (off by 0.2).
- Lime: lawn (cool-season grass) 9.2 lb/100 sq ft over 2 applications; vegetable garden 9.2 lb/100 sq ft over 2 applications; tomatoes 9.2 lb/100 sq ft over 2 applications; roses 9.2 lb/100 sq ft over 2 applications; pink hydrangeas 5.8 lb/100 sq ft over 2 applications.
What to do next
If your test confirms pH near 5.74, spread about 92 lb of ground limestone per 1,000 sq ft of vegetable bed in 2 doses, ideally in fall.
How mixed the soil is
Of the 562,542 surveyed acres in Cowlitz, WA, 70% are moderately acidic (5.5-6.5), 23% are strongly acidic (below 5.5), 8% are near neutral (6.5-7.3). Mapped soils run from pH 5 to 6.7, a spread of 1.7 units across 277 soil components. 70% 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 16.7% clay and 5.83% organic matter, which this site treats as clay. At 5.83% 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.
Cowlitz against the rest of Washington
pH 5.74 is 0.67 below the Washington median of 6.41. 16 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: Skagit (5.58), Clark (5.62), Island (5.67), Snohomish (5.68), Thurston (5.76), Skamania (5.86), Spokane (6.41), Okanogan (6.45).
The range in Washington runs from Grays Harbor at 4.93 to Adams at 7.45; Cowlitz sits 32% of the way up.