Soil pH in Skagit, WA: Lime or Sulfur?
Typical topsoil pH in Skagit, WA
Typical topsoil in Skagit, WA is pH 5.58, too acidic for vegetable garden. Expect roughly 10.4 lb of lime per 100 sq ft, but only after a soil test confirms it.
What Skagit needs, by plant
- Already in range: potatoes, strawberries, azaleas and rhododendrons.
- Just outside, test first: blueberries (off by 0.1), blue hydrangeas (off by 0.1).
- Lime: lawn (cool-season grass) 10.4 lb/100 sq ft over 3 applications; vegetable garden 10.4 lb/100 sq ft over 3 applications; tomatoes 10.4 lb/100 sq ft over 3 applications; roses 10.4 lb/100 sq ft over 3 applications; pink hydrangeas 8 lb/100 sq ft over 2 applications.
What to do next
If your test confirms pH near 5.58, spread about 104 lb of ground limestone per 1,000 sq ft of vegetable bed in 3 doses, ideally in fall.
How mixed the soil is
Of the 677,438 surveyed acres in Skagit, WA, 42% are strongly acidic (below 5.5), 41% are moderately acidic (5.5-6.5), 18% are near neutral (6.5-7.3). Mapped soils run from pH 4.1 to 7, a spread of 2.9 units across 328 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 11% clay and 6.24% organic matter, which this site treats as clay. At 6.24% 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.
Skagit against the rest of Washington
pH 5.58 is 0.83 below the Washington median of 6.41. 12 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: King (5.45), Pierce (5.48), Kitsap (5.49), San Juan (5.56), Clark (5.62), Island (5.67), Snohomish (5.68), Cowlitz (5.74).
The range in Washington runs from Grays Harbor at 4.93 to Adams at 7.45; Skagit sits 26% of the way up.